# First Insights on the Behavior of Foamed Polystyrenes in the Marine Environment and on the Ways to Reduce This Pollution

Mikaël Kedzierski, Gwenaël Le Maguer, Audrey Maffessoli, Stéphane Bruzaud

► To cite this version:

Mikaël Kedzierski, Gwenaël Le Maguer, Audrey Maffessoli, Stéphane Bruzaud. First Insights on the Behavior of Foamed Polystyrenes in the Marine Environment and on the Ways to Reduce This Pollution. 7.1, Université Bretagne Sud. 2021, pp.214. hal-05206440

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OCEAN
WISE

Reducing
EPS marine litter
in the North East
Atlantic

13/04/2021

Oceanwise

WP 7 - Mitigating EPS impact:

Living Labs of Eco-innovation

# First insights on the behavior of foamed polystyrenes in the marine environment and on the ways to reduce this pollution

Mikaël Kedzierski, Gwenaël Le Maguer, Audrey

Maffessoli, Stéphane Bruzaud

Institut de Recherche Dupuy de Lôme (IRDL)
<figure><img src="image_3.png" /></figure>

**OCEAN**
**WISE**

Reducing
EPS marine litter
in the North East
Atlantic

# Reducing EPS and XPS Marine litter in the north east Atlantic

## WP 7 - Mitigating EPS impact: Living Labs of Eco-innovation

### 7.1: Testing key properties of alternative materials to EPS

### Disclaimer

This document covers activities implemented with the financial assistance of the INTERREG Atlantic Area. It only reflects the author's view, thus the Atlantic Area Programme authorities are not liable for any use that may be made of the information contained therein.
<table><tr><td>Work Package</td><td>7</td></tr><tr><td>Action</td><td>7.1</td></tr><tr><td>Last updated</td><td>12/04/2021</td></tr><tr><td>Version</td><td>1.0</td></tr><tr><td>Organisation</td><td>Institut de Recherche Dupuy de Lôme (IRDL)</td></tr></table>
FIRST INSIGHTS ON THE BEHAVIOR OF FOAMED
POLYSTYRENES IN THE MARINE ENVIRONMENT
AND ON THE WAYS TO REDUCE THIS POLLUTION

Mikaël Kedzierski, Gwenaël Le Maguer, Audrey Maffessoli, Stéphane Bruzaud

Report on the studies carried out on behalf of the OceanWise Interreg
project by the Institut de Recherche Dupuy de Lôme (IRDL).

This report was coordinated and mainly produced by the IRDL members. Other partners
may have occasionally contributed to certain sections of the report and are listed at the
beginning of each section. This report is part of WP 7 of the OceanWise project. Other
reports have been produced on other aspects of WP 7.

**Citation:** Kedzierski, M., Le Maguer, G., Maffessoli, A., Bruzaud, S., 2021.

First insights on the behavior of foamed polystyrenes in the marine environment
and on the ways to reduce this pollution. OceanWise reports. 214p.
# AUTHORS

## Main contributors

* **Mikaël Kedzierski** (IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France)

* Conceptualization

* Methodology

* Validation

* Investigation

* Formal analysis

* Writing - Original Draft

* Writing - Review & Editing

* Supervision

* **Gwenaël Le Maguer** (Archipel Institute, Université Bretagne Sud, 56100 Lorient, France)

* Writing - Review & Editing

* Project administration

* **Audrey Maffessoli**

* Project administration

* Resources

* **Stéphane Bruzaud** (IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France)

* Writing - Review & Editing

* Supervision

* Project administration

* Funding acquisition
## Other contributors

### Part 2

* **Maïwenn Le Gall** (IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France)

### Part 3

* **Benjamin Lechat** (IRDL UMR CNRS 6027, Université Bretagne Sud, 56000 Vannes, France)

* **Olivier Sire** (IRDL UMR CNRS 6027, Université Bretagne Sud, 56000 Vannes, France)

* **Véronique Le Tilly** (IRDL UMR CNRS 6027, Université Bretagne Sud, 56000 Vannes, France)

### Part 4

* **Benjamin Gallard** (C2MA, Ecole des Mines d'Alès, Alès, France)

* **Anne Bergeret** (C2MA, Ecole des Mines d'Alès, Alès, France)

### Part 5

* **Edgar Pigeon** (IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France)

### Part 6

* **Emeric Lelu** (IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France)

### Part 7

* **Dalyal Copin** (Institut Régional des Matériaux Avancés, 56100 Lorient, France)

### Part 8

* **Dominique Frère** (TEMOS UMR CNRS 9016, Université Bretagne Sud, 56100 Lorient, France)
Contact

Dr. Mikaël Kedzierski

Université Bretagne Sud

Centre de Recherche C. HUYGENS

Rue de Saint-Maudé - BP 92116

F-56321 LORIENT Cedex

mikael.kedzierski@univ-ubs.fr
# TABLES
TABLE OF CONTENTS

TABLE OF CONTENTS

FIRST INSIGHTS ON THE BEHAVIOR OF FOAMED POLYSTYRENES IN THE
MARINE ENVIRONMENT AND ON THE WAYS TO REDUCE THIS POLLUTION...... 0

AUTHORS.................................................................................................................. 2

Main contributors ........................................................................................................ 2

Other contributors ........................................................................................................ 3

Contact................................................................................................................................. 4

TABLES...................................................................................................................... 5

TABLE OF CONTENTS........................................................................................................ 6

TABLE OF ILLUSTRATIONS................................................................................................ 12

TABLE OF TABLES........................................................................................................ 16

TABLE OF EQUATIONS.................................................................................................... 17

INTRODUCTION............................................................................................................ 20

INTRODUCTION............................................................................................................ 20

1. The OceanWise project........................................................................................................ 20

1.1. Main Objective .................................................................................................................. 20

1.2. A common Challenge ........................................................................................................ 22

1.3. An opportunity .................................................................................................................. 24

1.4. A transnational approach.................................................................................................... 25

1.5. Workpackages .................................................................................................................. 27

2. Mitigating EPS impact: Living Labs of Eco-innovation (LLEco) .................................................. 28

2.1. Presentation of WP 7 ........................................................................................................ 28

2.2. WP7 actions.................................................................................................................... 28

2.3. Presentation of the report.................................................................................................... 30
TABLE OF CONTENTS

INSIGHT OF THE BEHAVIOR OF POLYSTYRENE IN THE MARINE

ENVIRONMENT .................................................................................................................. 34

PART 1. EPS and XPS ageing in the natural environment .................................................. 35

1. Introduction.................................................................................................................. 35

2. Materials and methods .................................................................................................. 36

2.1. Samples .................................................................................................................. 36

2.2. Study sites.................................................................................................................. 37

2.3. Meteorological conditions over the study period .................................................... 41

2.4. methods .................................................................................................................. 44

3. Results.......................................................................................................................... 47

3.1. Sample thickness variation .................................................................................. 47

3.2. Evolution of the porosity .................................................................................... 48

3.3. Mechanic properties of polystyrene samples.................................................... 49

3.4. FTIR Index ................................................................................................................ 53

4. Synthesis .................................................................................................................... 56

4.1. Marine ageing versus atmospheric ageing.......................................................... 56

4.2. Duration of the study .......................................................................................... 57

4.3. Differences between materials............................................................................ 58

5. Conclusion .................................................................................................................... 58

6. Supplementary materials.......................................................................................... 59

6.1. Mechanic properties of polystyrene samples.................................................... 59

6.2. FTIR indexes ............................................................................................................ 61

PART 2. Accelerated mechanical abrasion of Expanded Polystyrene........................................ 64

Abstract ............................................................................................................................ 64

Keywords............................................................................................................................ 64

1. Introduction.................................................................................................................. 65

2. Materials and methods .................................................................................................. 67

2.1. Samples .................................................................................................................. 67

2.2. Experimental conditions .................................................................................... 67
TABLE OF CONTENTS

<table><tr><td>2.3.</td><td>Microscopy observation</td><td>68</td></tr><tr><td>3.</td><td>Results and discussion</td><td>68</td></tr><tr><td>3.1.</td><td>Weight variation</td><td>68</td></tr><tr><td>3.2.</td><td>Variation of dimensions</td><td>71</td></tr><tr><td>3.3.</td><td>Microscopy observations</td><td>73</td></tr><tr><td>4.</td><td>Conclusion</td><td>76</td></tr><tr><td colspan="2">References</td><td>78</td></tr></table>

PART 3. Microplastic contamination of packaged meat: occurrence and associated risks..... 80

<table><tr><td>Abstract</td><td>80</td></tr><tr><td>Keywords</td><td>80</td></tr><tr><td>1. Introduction</td><td>81</td></tr><tr><td>2. Materials and methods</td><td>83</td></tr><tr><td>2.1. Sample collection and preparation</td><td>83</td></tr><tr><td>2.2. Isolation, visual characterization, and identification of microplastics</td><td>85</td></tr><tr><td>2.3. Estimated per capita consumption of microplastics and statistical analysis</td><td>85</td></tr><tr><td>3. Results</td><td>86</td></tr><tr><td>3.1. Particles</td><td>86</td></tr><tr><td>3.2. Fibres</td><td>90</td></tr><tr><td>4. Discussion</td><td>91</td></tr><tr><td>4.1. Contamination of the surface of meat products with microplastics</td><td>91</td></tr><tr><td>4.2. Ingesting MP-XPS: A threat to human health?</td><td>92</td></tr><tr><td>4.3. Microfibres: Another contaminant</td><td>96</td></tr><tr><td>5. Conclusion</td><td>97</td></tr><tr><td>References</td><td>99</td></tr></table>

WAYS TO REDUCE POLYSTYRENE WASTES ................................................................. 108

PART 4. Production of foamed PLA................................................................................ 109

<table><tr><td>1. Introduction</td><td>109</td></tr><tr><td>2. Materials and methods</td><td>110</td></tr><tr><td>2.1. Materials</td><td>110</td></tr></table>
TABLE OF CONTENTS

<table><tr><td>2.2.</td><td>Characterization</td><td>112</td></tr><tr><td>3.</td><td>Results</td><td>112</td></tr><tr><td>3.1.</td><td>Void fraction</td><td>112</td></tr><tr><td>3.2.</td><td>Sample observation</td><td>113</td></tr><tr><td>4.</td><td>Conclusion</td><td>115</td></tr><tr><td colspan="2">References</td><td>116</td></tr></table>

PART 5. Study of the properties of three objects made of expanded polystyrene and comparison with foamed PLA

<table><tr><td>1.</td><td>Introduction</td><td>118</td></tr><tr><td>2.</td><td>Materials and methods</td><td>118</td></tr><tr><td>2.1.</td><td>Samples</td><td>118</td></tr><tr><td>2.2.</td><td>Differential scanning calorimetry (DSC)</td><td>118</td></tr><tr><td>2.3.</td><td>Energy dispersive X-ray spectroscopy</td><td>119</td></tr><tr><td>2.4.</td><td>Porosity</td><td>119</td></tr><tr><td>2.5.</td><td>Compression tests</td><td>120</td></tr><tr><td>3.</td><td>Results and discussion</td><td>120</td></tr><tr><td>3.1.</td><td>DSC</td><td>120</td></tr><tr><td>3.2.</td><td>SEM-EDX</td><td>121</td></tr><tr><td>3.3.</td><td>Porosity</td><td>123</td></tr><tr><td>3.4.</td><td>Compression tests</td><td>124</td></tr><tr><td>4.</td><td>Conclusion</td><td>126</td></tr></table>

PART 6. Aging of foamed polylactic acid (PLA) in marine and atmospheric environments

<table><tr><td colspan="2">Abstract</td><td>127</td></tr><tr><td>1.</td><td>Introduction</td><td>127</td></tr><tr><td>2.</td><td>Materials and Methods</td><td>129</td></tr><tr><td>2.1.</td><td>Polylactic acid</td><td>129</td></tr><tr><td>2.2.</td><td>Aging sites</td><td>129</td></tr><tr><td>2.3.</td><td>Meteorological conditions over the study period</td><td>130</td></tr><tr><td>2.4.</td><td>FTIR</td><td>131</td></tr><tr><td>2.5.</td><td>Porosity</td><td>132</td></tr></table>
TABLE OF CONTENTS

<table><tr><td>2.6.</td><td>Tensile test</td><td>133</td></tr><tr><td>2.7.</td><td>Scanning electronic microscope (SEM-EDX)</td><td>134</td></tr><tr><td>3.</td><td>Results</td><td>134</td></tr><tr><td>3.1.</td><td>FTIR</td><td>134</td></tr><tr><td>3.2.</td><td>Porosity</td><td>135</td></tr><tr><td>3.3.</td><td>Tensile test</td><td>138</td></tr><tr><td>3.4.</td><td>Scanning electronic microscope (SEM-EDX)</td><td>140</td></tr><tr><td>4.</td><td>Discussion and conclusion</td><td>143</td></tr><tr><td colspan="2">Reference</td><td>144</td></tr></table>

Part 7. Assessment of biodegradation in seawater at the sediment-water interface 146

<table><tr><td>1.</td><td>Introduction</td><td>146</td></tr><tr><td>2.</td><td>Material and methods</td><td>146</td></tr><tr><td>2.1.</td><td>Samples presentation</td><td>146</td></tr><tr><td>2.2.</td><td>Method</td><td>147</td></tr><tr><td>3.</td><td>Results</td><td>147</td></tr><tr><td>4.</td><td>Conclusions</td><td>151</td></tr></table>

Part 8. Why are there plastics in the natural environment? Understanding the roots of our personal plastic waste management behaviours 152

<table><tr><td>Abstract</td><td>152</td></tr><tr><td>Keywords</td><td>153</td></tr><tr><td>1.</td><td>Introduction</td><td>153</td></tr><tr><td>1.1.</td><td>The rise of plastic packaging</td><td>153</td></tr><tr><td>1.2.</td><td>Voluntary abandonment of plastic waste: a source of plastics pollution</td><td>155</td></tr><tr><td>1.3.</td><td>From plastic waste to pollution</td><td>155</td></tr><tr><td>1.4.</td><td>Objectives</td><td>157</td></tr><tr><td>2.</td><td>A cost-benefit balance that modulates our individual plastic waste management behaviours</td><td>157</td></tr><tr><td>2.1.</td><td>Risk avoidance mechanisms: general cases</td><td>157</td></tr><tr><td>2.2.</td><td>Out of sight, out of mind?</td><td>158</td></tr><tr><td>2.3.</td><td>Two particular cases?</td><td>160</td></tr><tr><td>3.</td><td>Uncontrolled landfilling</td><td>161</td></tr></table>
TABLE OF CONTENTS

<table><tr><td>3.1.</td><td>A behaviour deeply rooted in time</td><td>162</td></tr><tr><td>3.2.</td><td>Resistance of populations to good waste management practices</td><td>162</td></tr><tr><td>4.</td><td>Reuse: a (lost) cultural legacy</td><td>166</td></tr><tr><td>4.1.</td><td>Management of ceramic packaging waste in the past</td><td>166</td></tr><tr><td>4.2.</td><td>The transition to the consumer society</td><td>167</td></tr><tr><td>4.3.</td><td>Reuse behaviour: an under-exploited source of innovation to improve plastic waste management?</td><td>168</td></tr><tr><td>5.</td><td>Synthesis and conclusions</td><td>170</td></tr><tr><td>5.1.</td><td>The weight of the consequences</td><td>170</td></tr><tr><td>5.2.</td><td>Behavioural issues</td><td>171</td></tr><tr><td>5.3.</td><td>Ways to reduce waste abandonment</td><td>172</td></tr><tr><td colspan="2">References</td><td>174</td></tr><tr><td colspan="2">CONCLUSION</td><td>186</td></tr><tr><td colspan="2">Conclusion</td><td>189</td></tr><tr><td colspan="2">REFERENCES</td><td>190</td></tr><tr><td colspan="2">References</td><td>190</td></tr></table>
TABLE OF ILLUSTRATIONS

TABLE OF ILLUSTRATIONS

Figure 1. OceanWise aims to jointly develop and implement a set of long-term measures to reduce the impact of expanded polystyrene (EPS) products as marine litter in the Atlantic Area.
21

Figure 2. Different types of consumer goods made of polystyrene will be specifically studied in the OceanWise project.
22

Figure 3. Marine litter composition by material (Source: OSPAR).
23

Figure 4. OceanWise is a European project with thirteen partners from five countries: Portugal, Spain, France, Ireland and the United Kingdom.
25

Figure 5. Project structure.
26

Figure 6. Materials selected for study. From left to right, a fish box lid, a food tray and an insulation plate.
37

Figure 7. Samples of polystyrene aged on the roof of the university.
38

Figure 8. Design of the aging support for polystyrene samples destined for the marine environment. Example of fish boxes (left) and insulation plates (right).
39

Figure 9. Plastic's ageing experimentation.
40

Figure 10. Installation of an ageing support in the net.
41

Figure 11. Vantage Pro2 Weather Station.
42

Figure 12. Measurements of the environmental conditions. A) Measurements of rainfall (mm) and marine and atmospheric temperatures (°C). B) Measurement of solar and UV radiations (W/m²).
44

Figure 13. Binocular loupe observation of a polystyrene sample. The pore walls are coloured with a black ink.
45

Figure 14. Sample thickness variation. CAP: Fish box; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean.
48
TABLE OF ILLUSTRATIONS

Figure 15. Evolution of the number average diameter of the porosity. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean. 49

Figure 16. Evolution the ratio of the Young's modulus (E) and its initial value (Eᵢ) for the different samples. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean. 51

Figure 17. Evolution of the ratio of the compressive strength (Rs) and its initial value (Rsᵢ) for the different samples. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean. 53

Figure 18. Evolution of the Carbonyl Index of the samples. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean. 54

Figure 19. Evolution of the 1010 Index of the samples. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean. 55

Figure 20. Evolution of the 1637 Index of the samples. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean. 56

Figure 21. Mass variations of the samples as a function of time and size range of the sand particles, and for dry and wet environments. 70

Figure 22. Volume variations of the samples as a function of time and size range of the sand particles, and for dry and wet environments. 73

Figure 23. Microscopic observation of an insulation plate sample aged with dry sand. 74

Figure 24. Microscopic observation of the isolation EPS after accelerated degradation in dry environment (125µm sand). 75

Figure 25. MP-XPS observed with a dissecting microscope (the Photoshop software was used to improve the image brightness). 87

Figure 26. Number of MP-XPS per kilogram of meat observed at the surface of and inside the food packaging for the different brands. 88
TABLE OF ILLUSTRATIONS

<table><tr><td>Figure 27. Amounts of microfibres per kilogram of packaged meat observed on the surface and inside of the food packaging examined. * Results that show statistical differences (p-value &lt; 0.05).</td><td>91</td></tr><tr><td>Figure 28. SEM images of the PLA plate section.</td><td>114</td></tr><tr><td>Figure 29. Measurement of precipitation (mm) and marine and atmospheric temperatures (°C).</td><td>131</td></tr><tr><td>Figure 30. Measurement of solar and UV radiations (W/m²).</td><td>131</td></tr><tr><td>Figure 31. Optical microscope image of PLA aged 6 months in the atmosphere and artificially coloured black to highlight changes in geometry.</td><td>132</td></tr><tr><td>Figure 32. Evolution of carbonyl indices of samples aged 1 year in marine and air environments.</td><td>135</td></tr><tr><td>Figure 33. Evolution of the number of mean diameter as a function of time for samples aged in air and sea environments.</td><td>138</td></tr><tr><td>Figure 34. Evolution of the young modulus as a function of time for samples aged in air and sea environments.</td><td>140</td></tr><tr><td>Figure 35. Observation under a scanning electron microscope of (a) unaged PLA (b) aged 6 months in air environment (c) aged 10 months in air environment (d) aged 12 months in air environment.</td><td>141</td></tr><tr><td>Figure 36. Observation under a scanning electron microscope of (a) PLA aged 6 months in marine environment (b) aged 10 months in marine environment (c) aged 12 months in marine environment with 500 µm.</td><td>142</td></tr><tr><td>Figure 37. Biodegradation rate of PLA foam in marine environment.</td><td>149</td></tr><tr><td>Figure 38. Biodegradation rate of PLA-PBAT in marine environment.</td><td>151</td></tr><tr><td>Figure 39. Time lines of packaging history (data from Berger, 2003; Risch, 2009).</td><td>154</td></tr></table>
TABLE OF TABLES

TABLE OF TABLES

<table><tr><td>Table 1. Young's modulus (E, GPa)</td><td>59</td></tr><tr><td>Table 2. Compressive strength (Rs, kPa)</td><td>60</td></tr><tr><td>Table 3. FTIR indexes</td><td>61</td></tr><tr><td>Table 4. Dimensions of the samples</td><td>67</td></tr><tr><td>Table 5. Sample characteristics</td><td>84</td></tr><tr><td>Table 6. Mass of MP-XPS per kilogram of meat for the different brands estimated from each density hypothesis</td><td>89</td></tr><tr><td>Table 7. Consumption of MP-XPS per person based on a meat consumption of 135 g/d/person</td><td>90</td></tr><tr><td>Table 8. Formulations carried out</td><td>111</td></tr><tr><td>Table 9. Condition of PLA extrusion tested</td><td>112</td></tr><tr><td>Table 10. Void fractions as a function of the different formulations</td><td>113</td></tr><tr><td>Table 11. Glass transition temperature (Tg) of the different materials tested</td><td>121</td></tr><tr><td>Table 12. Atomic percent (%)</td><td>123</td></tr><tr><td>Table 13. Characteristics of the porosity</td><td>124</td></tr><tr><td>Table 14. Mechanical properties of the materials</td><td>125</td></tr><tr><td>Table 15. Evolution of the dn for PLA samples aged in atmospheric and marine environment</td><td>137</td></tr><tr><td>Table 16. Evolution of the young modulus, stress at break, strain at break during air aging</td><td>138</td></tr><tr><td>Table 17. Evolution of the young modulus, stress at break, strain at break during marine aging</td><td>139</td></tr><tr><td>Table 18. Extrapolation using Hills (3 constants)</td><td>148</td></tr><tr><td>Table 19. Extrapolation using Boltzmann double sigmoid</td><td>150</td></tr></table>
TABLE OF EQUATIONS

TABLE OF EQUATIONS

<table><tr><td>di = 2Aiπ (Equation 1)</td><td>45</td></tr><tr><td>pi = Zx - LxZy - LyZxZy (Equation 2)</td><td>45</td></tr><tr><td>dn = dipini (Equation 3)</td><td>46</td></tr><tr><td>CI = 1740/694A (Equation 4)</td><td>46</td></tr><tr><td>1010I = 1010A/694A (Equation 5)</td><td>47</td></tr><tr><td>1637I = 1637A/694A (Equation 6)</td><td>47</td></tr><tr><td>Nt = NMP/m*m<sub>t</sub> (Equation 7)</td><td>85</td></tr><tr><td>Vf = 1 - ρfρp * 100 (Equation 8)</td><td>112</td></tr><tr><td>CI = 1740A / 1450A (Equation 9)</td><td>132</td></tr><tr><td>di = 2Aiπ (Equation 10)</td><td>133</td></tr><tr><td>pi = Zx - LxZy - LyZxZy (Equation 11)</td><td>133</td></tr><tr><td>dn = dipini1pi (Equation 12)</td><td>133</td></tr></table>
TABLE OF EQUATIONS
# INTRODUCTION

## 1. The OceanWise Project

### 1.1. Main Objective

OceanWise aims to jointly develop and implement a set of long-term measures to reduce the impact of expanded polystyrene (EPS) products as marine litter in the Atlantic Area (AA). Based on resource-efficiency, participatory methods and Circular Economy (CE) principles, it will generate new and best practice within sectors using, manufacturing or recycling EPS.

To achieve this, it is intended to explore new ways to (Figure 1):

* Identify EPS products and their source that are more likely to reach the marine environment and impact on its ecosystems;

* Propose and test plausible options (reduce, reuse, recycle, recover) to achieve better environmental outcomes within different sectors;

* Engage producer and designer communities on the sustainability of specific applications and to explore more circular models;

* Develop CE-oriented methodologies to assess new opportunities, barriers and policy options.
<figure><img src="image_4.png" /><figcaption>Figure 1. OceanWise aims to jointly develop and implement a set of long-term measures to reduce the impact of expanded polystyrene (EPS) products as marine litter in the Atlantic Area.</figcaption></figure>

This proposal is driven by the EU-Marine Strategy Framework Directive (MSFD) and the OSPAR Convention's Regional Action Plan on Marine Litter (RAP-ML). There is a strong impetus to devolve ideas and commitments to national, regional & local political levels. In particular, in alignment with the OSPAR RAP-ML, the project will support RAP action no.49, focused on 'the prevalence and impact of EPS in the marine environment, and engage with industry to make proposals for alternative materials and/or how to reduce its impacts.' The objectives of OceanWise align with the CE Package for Europe.

Concerning the first way (i.e. "Identify EPS products and their source that are more likely to reach the marine environment and impact on its ecosystems"), four families of polystyrene objects were selected by the OceanWise consortium (Figure 2). These are those related to:
* the fishing industry;

* the food industry;

* consumer goods;

* goods for open-air festivals and tourism.

<figure><img src="image_5.png" /><figcaption>Figure 2. Different types of consumer goods made of polystyrene will be specifically studied in the OceanWise project.</figcaption></figure>

## 1.2. A common Challenge

Expanded polystyrene (EPS) in the marine environment is a common problem around EU Atlantic coasts and sea. It is of particular concern due to the large amounts found on beaches and the potential hazard it poses to marine wildlife and, potentially, to human health (Figure 3). EPS is a plastic foam material used globally in packaging and insulation including as food trays, drink/food containers and fish boxes. Although EPS is recyclable, it seldom is, due to the low cost-effectiveness of transporting and recycling expanded material.
<figure><img src="image_6.png" /><figcaption>Figure 3. Marine litter composition by material (Source: OSPAR).</figcaption></figure>

EPS weighs little compared to its volume, which makes it very cost-effective when compared to other packaging options. It is also deemed safe for use with food. Its lightness means EPS is easily blown from garbage bins and landfills.

Furthermore, it is non-biodegradable and tends to fragment, with small pieces travelling long distances. Thus it can become marine litter and fragment into microplastics that persist in the marine environment and contaminate the food chain. According to OSPAR beach monitoring surveys, small plastic/ polystyrene pieces are among the most common type of marine litter items, i.e. found in the highest numbers on the regular reference beaches, and account for up to 30% of total items.
OceanWise intends to address this challenge by developing knowledge to reduce the impacts
of EPS items and by raising the ability of competent authorities and key sectors across the
Atlantic region to implement more sustainable management options.

1.3. *An opportunity*

OceanWise is a unique attempt to tackle a specific marine litter item requiring immediate action (i.e. EPS products). This approach will integrate the recent path of transition to a circular economy by tackling EPS litter from its origins, addressing the entire life-cycle of products based on interaction with the industry and other key sectors using EPS, to seek their active involvement to find solutions from the root level. OceanWise represents the first collaborative attempt to address EPS as a source of ML in the Atlantic Area (Figure 4). It will develop concrete steps towards prevention of this environmental pressure, as well as foster innovation and more sustainable practices. In order to achieve this, OceanWise intends to set up in each partner region Living Labs of Eco-innovation (LLEco) to address the EPS applications challenges. These living labs will mobilise and engage in dialogue with various private and public sectors that produce, use and manage this material. These will be key to integrate circularity knowledge on EPS and its alternatives and to find new and practical options to reduce, reuse, recycle and recover EPS products; significant as an essential pillar for the circular economy. By jointly attempting to reduce “escapes” or inputs of EPS into the marine environment, the project will not only contribute to reducing impacts that ML exerts on natural ecosystems and vital economic sectors but constitute a concrete, motivated effort to improve management.
<figure><img src="image_7.png" /><figcaption>Figure 4. OceanWise is a European project with thirteen partners from five countries: Portugal, Spain, France, Ireland and the United Kingdom.</figcaption></figure>

OceanWise comprises 13 partners ranging from national governmental organizations and operational agencies to knowledge centres from the five countries. In addition, the OSPAR Secretariat has joined the partnership as associated partner, adding institutional support and advice to the project, as the OSPAR Convention includes all the countries of the North-East Atlantic area.

1.4. A transnational approach

EPS litter is common in the EU Atlantic coastal and marine environment and has a
transboundary impact. It circulates with oceanic currents and can affect areas distant from its
origin. Its nature and potentially harmful impact call for joint effort across the region.

Addressing this is key to implementation of the MSFD's aim of reaching/maintaining Good Environmental Status (GES) for the marine ecosystem. It also contributes to the implementation of the OSPAR Regional Action Plan for marine litter. It is recognised that effective reduction of EPS marine litter in the North-East Atlantic can only be achieved co-operatively and transnationally. OceanWise will seek to carry out participatory processes to engage and mobilize key stakeholders across the region (Figure 5). A living labs approach will be used to build common understanding on the varying applications of EPS across the region and create a dynamic for the emergence of communities able to work autonomously in the pursuit of sustainability in the reduction and responsible co-management of EPS-based products. The knowledge gained from the collaborative processes will promote responsible attitudes and the build-up of a circular economy cluster. It will bring together transnational technical and lay knowledge on new transdisciplinary collective solutions and practical options which benefit from economies of scale by transnational uptake. These will be valuable for building common understanding and pursuing joint management pathways.

<figure><img src="image_8.png" /><figcaption>Figure 5. Project structure.</figcaption></figure>
1.5. Workpackages

The project consists of 8 workpackages. The first workpackage deals with the coordination of
all aspects of OceanWise - administrative, financial, promotional and operational - will be
assured on behalf of all beneficiaries by DGRM, who will be supported by an external project
coordination office (EPCO). The second workpackage is directed by DGRM that is responsible
for communication activities for OceanWise. Workpackage 3, led by UCC – MaREI, ensures
that OceanWise activities address key audiences at regional level; specifically, including
marine environment protection, innovation, and sectors (e.g. fisheries) that rely upon marine
ecosystem services. The workpackage 4 aims to improve interaction and collaboration by
building a collaborative governance mode threw the Interactive Stakeholders' Platform. WP5
seeks to provide a common knowledge base on PES and its alternatives, not only in terms of
use, applications and production, but also in terms of stakeholders and existing policies,
incentives and producer responsibility systems related to the topic. The WP6 addresses the
following 3 actions: the review of circularity indicators / tools, the review of models and the
circularity assessment of current solutions. The WP7 aims to evaluate the promising solutions
to replace the use of EPS products, through analyses and real-life living-labs of eco-innovation
on potential harm issues and usability pilots with target industries. It is particularly in this
workpackage, fed by the decisions of the consortium and the information from the other
workpackages, that this document is embedded. This workpackage will be described in more
detail in the following section. Last, WP8 will collate the lessons learned from the OceanWise
project and compile them into a publicly available report. The report will include
recommendations for the future management of EPS with the aim of reducing inputs to the
marine environment. It will take into account the concerns of stakeholders and build on the
lessons learned to maximise the impact of the project.
## 2. Mitigating EPS impact: Living Labs of Eco-innovation (LLEco)

### 2.1. Presentation of WP 7

The purpose of the WP7 is to evaluate the promising solutions to replace the use of EPS products, through analyses and real-life living-labs of eco-innovation on potential harm issues and usability pilots with target industries. The materials and products (or prototypes) to be studied will be identified in WP4 and WP5. Key properties regarding the aimed applications will be assessed and compared with EPS ones: functional properties, durability and biodegradability, environmental impact and ecotoxicity, costs.

Mainly, the functional properties evaluations will be led by UBS with help from Seabird, and BIM and CETMAR helping to identify the key requirements regarding the aimed applications. CEDRE and CEFAS will focus on the environmental impact and ecotoxicity assessment and comparison to EPS.

BIM and CETMAR will coordinate the field trials connecting with stakeholders. BIM and CETMAR will focus on the seafood sector, while other partners will target other sectors, namely fisheries and packaging (food and general) in Portugal.

WP7 is divided into three actions.

#### 2.2.WP7 actions

##### 2.2.1. Action 1: Testing key properties of alternative materials to EPS

A variety of properties of the most interesting/promising alternative materials selected in WP5 will be examined regarding the possible applications:

- mechanical properties and durability

- aging in the use conditions (marine environment, UV resistance)

- biodegradability
The results will provide key inputs for WP6, 7.3 and 8.

The aim of this action is to propose a selection of bioplastics and eco-friendly materials that are
new options for EPS substitution: relevant properties in regard with the aimed applications;
(bio)degradation rate in marine conditions; and environmental impact in comparison with EPS.

2.2.2. Action 2: Assessment and comparison of the potential impact and ecotoxicity of EPS
and new EPS substitute

It aims to evaluate and compare the potential impact of EPS and new EPS substitute. Firstly,
through lab and fields experimentations aiming at knowing POPs concentration and ad- and de-
sorption kinetics, and secondly, through OSPAR tests (microalgae and copepods) and
experiments in dedicated tanks with fish (Dicentrarchus labrax) to assess the potential
ecotoxicity.

The report will identify what POPs are preferentially adsorbed at which concentrations in
various environment; assess the POPs sorption kinetics and assess potential seafood
contamination.

2.2.3. Action 3: Living-labs of eco-innovation

The action focuses on field tests with alternative products, prototypes, materials, identified in
the WP5 and WP7.1 which prove the technical and commercial viability in comparison with
the current uses of EPS. They'll be performed in the aquaculture sector (transport of oyster
seeds or another task) and the food marketing/distribution sector, based on WP4 guidance. A
quality analysis will be made at arrival. The tests could be extended to alternative ways of EPS
treatment and reuse.
If this succeeds the specific trials will transmit confidence to the packaging manufacturers, to
the aquaculture and food sectors and to the recycling operators to promote the use of the
alternative materials.

## 2.3.Presentation of the report

### 2.3.1. Who are we?

The IRDL is the referent laboratory for mechanical systems in Europe related to the engineering of materials and systems used in industrial sectors related to the automobile, energy, aeronautics, health and transport industries and more specifically to all fields with a dynamic interaction with the marine environment, such as shipbuilding and offshore construction and marine energies. IRDL is divided in different research hub and the hub 1 is dedicated to research activities focused on showing and characterising polymer, fibrillar or mineral meso-structures with dynamic structuring in the presence of interfaces.

The main skills and expertise are in the field of physical chemistry and transformation processes aimed at controlling changes of phase (percolation of fillers, polymer or polymer-solvent mixtures), the multi-scale structuring (of networks of fibres, nanofillers) and being able to measure the consequences on the properties of use of the materials. The aim of these fundamental studies is therefore to design hybrid materials with controlled properties, such as functional nanocomposites, smart or stimulus-responsive composites or polymers, controlled biodegradability biopolymers or high performance and durable biocomposites.

The Archipel Institute ("Institut citoyen d'études maritimes et littorals") is a privileged interface between the UBS and the institutional, socio-economic and associative actors in the maritime and coastal field. It aims i) to facilitate and accelerate the circulation of information, the crossing of networks, the setting up of relationships within the university and with stakeholders, ii) to favour the emergence of projects and to support their realization (research development and
innovation projects; educational and cultural projects). The Archipel Institute is based on an inclusive, federating, participative dynamic, open to the whole community of staff and students of the UBS, and to its partners: academic, institutional, professional, associations, representatives of civil society, etc.

2.3.2. *Organization of the report*

The different parts of this report belong mainly to Action 1 of WP7. Two main lines of reflection will be developed. The first one will focus on the behaviour of polystyrene in the marine environment. This first axis is itself divided into three parts. Thus, the first part will focus on the acquisition of data on the ageing of polystyrene foams in the natural environment. The second part will focus on the behaviour of polystyrene foamed in the accelerated mechanical abrasion of Expanded Polystyrene. The aim will be to study the ageing of different polystyrene foams under both atmospheric and marine conditions. The objective here will be to try to reproduce the mechanical wear of the polystyrene debris at the beaches. The third part deals with the discovery of microplastics from foamed polystyrene food trays and the associated risks.

This part has been published in the scientific journal "Food Packaging and Shelf Life".

The second axis will deal with ways to reduce polystyrene waste. More specifically, the different parts that make up this axis deal with the relevance of using foamed PLA (Polylactic Acid) to help reduce the use of polystyrene foam. This biodegradable polymer was chosen by the consortium because, at the beginning of the project, it was the only one known to be relatively easily foamed (SEABIRD, 2020, 2019). Thus, part 4 deals with the sample production of foamed PLA samples. Part 5 compares some physical and chemical properties of different foamed polystyrenes with the foamed PLA sample. Part 6 studies the ageing and degradation of foamed PLA in marine and atmospheric environments. Part 7 presents the results of laboratory biodegradation tests on two foamed biopolymers. Finally, the last part opens up the question of how to reduce this type of pollution a little more widely. This part, published in
2020 in the scientific journal "Science of the Total Environment" attempts to suggest ways to
explain our individual behaviour in relation to plastic waste management.

Finally, a conclusion summarises the main results obtained in this work.

It should be noted that each part can be read independently. It will therefore appear to a reader
reading the entire report that some parts or information may be redundant.
INSIGHT OF THE BEHAVIOR OF POLYSTYRENE IN
THE MARINE ENVIRONMENT
## PART 1. EPS and XPS ageing in the natural environment

Mikaël Kedzierski<sup>a</sup>, Gwénaël Le Maguer<sup>b</sup>, Stéphane Bruzaud<sup>a</sup>,

### 1. Introduction

The main objective of workpackage 7 is to evaluate the most promising alternative solutions to replace polystyrene in certain uses. This involves, among other things, gaining a better understanding of the behaviour of these alternatives in the marine environment, particularly with regard to their ageing and degradation. It is indeed necessary to ensure that the alternative materials proposed are more virtuous than polystyrene in similar environmental conditions. Thus, the ageing behaviour of these alternative materials in the natural environment must be better understood and be able to be compared with that of polystyrene. However, it should be noted that although the ageing behaviour of polystyrene in the air environment is relatively well studied from a scientific point of view, its behaviour in the marine environment is the subject of few publications. The first stage of this work therefore consists of acquiring these initial ageing data on polystyrene objects aged in the marine environment. At the same time, samples of the same nature must also be aged in the air to determine whether the ageing behaviour of polystyrene in the marine and air environment is similar. These data can then be used as framing data to compare ageing test results obtained on alternative materials to polystyrene.

The objective of this first part is therefore to acquire these framing data. It will thus be possible to better understand the ageing behaviour of the polystyrene samples selected by the members of the OceanWise project. For this purpose, samples coming from different types of polystyrene objects have been placed in two types of environment: atmospheric and marine. The collected samples were then characterised using different analytical techniques.

<footnote><sup>a</sup> IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France</footnote>

<footnote><sup>b</sup> Archipel Institute, Université Bretagne Sud, 56100 Lorient, France</footnote>
## 2. Materials and methods

### 2.1. *Samples*

The different partners of the OceanWise consortium have chosen to target three types of polystyrene use: transportation of perishable goods, building insulation and human food packaging (Figure 6). In the first case, the consortium has chosen to target fish boxes, an object widely used in fishing ports and which can be found in the natural environment. Here, the samples used in this study come from EPS fish box lids (Styropack brand) collected in polystyrene recovery bins from the fishing port of Keroman (Lorient, France). In the second case, EPS insulation plates (Depron brand) used to thermally insulate buildings were chosen. This type of insulation plate is often torn off from buildings during natural disasters (flooding, hurricanes, tsunami). Finally, extruded polystyrene (XPS) trays were chosen by the consortium to illustrate the third case (Inde Plastik). For these different materials, no information on chemical composition or processing conditions is available.

The experiment was designed for a one-year follow-up, from September 2018 to September 2019. Polystyrene samples were collected every 2 months.
<figure><img src="image_9.png" /><figcaption>Figure 6. Materials selected for study. From left to right, a fish box lid, a food tray and an insulation plate.</figcaption></figure>

## 2.2. Study sites

### 2.2.1. Atmospheric ageing

The site dedicated to atmospheric ageing is located on the roof of the research centre of the Université Bretagne Sud in Lorient (47°44′50.80″ N, 3°23′42.06″ W ; France) (Figure 7). The samples were placed in polyethylene crates and tilted by 5°.
<figure><img src="image_10.png" /><figcaption>Figure 7. Samples of polystyrene aged on the roof of the university.</figcaption></figure>

2.2.2. Marine ageing

The plastic samples were threaded onto metal rods and held in place with nuts (Figure 8). A gap of a few centimeters is left between each polystyrene sample to allow good water circulation. Thus, six plastic samples are arranged per dispositive, with one dispositive being taken each month for each type of polystyrene sample.
<figure><img src="image_11.png" /><figcaption>Figure 8. Design of the aging support for polystyrene samples destined for the marine environment. Example of fish boxes (left) and insulation plates (right).</figcaption></figure>

The samples were placed in the port of Kernevel (GPS coordinates: 47°43′18.33″ N, 3°22′06.15″ W) located in the bay of Lorient, 3 km south of the city of Lorient and 2 km north of the city of Larmor-Plage (Figure 9A) (Kedzierski et al., 2018). The port of Kernevel is mainly constituted by floating docks that can accommodate up to 1,100 pleasure boats. Plastic samples were placed under a floating dock in a net (Figure 9B).
<figure><img src="image_12.png" /><figcaption>Figure 9. Plastic's ageing experimentation.</figcaption></figure>

A) Kernevel harbor is located in the Bay of Lorient (France). B) The plastic samples are stored in lantern nets under the sea surface.

The net has been installed in the marine environment since November 2015 and has since been largely colonized by living organisms (e.g. algae, marine invertebrates) (Figure 10). The net was immersed under the floating dock at a depth of 1 to 2 meters below the surface and at all tide levels. The distance from the sea floor varied between 1 and 7 meters depending on the tide.
<figure><img src="image_13.png" /><figcaption>Figure 10. Installation of an ageing support in the net.</figcaption></figure>

## 2.3. Meteorological conditions over the study period

### 2.3.1. Weather station

Weather measurements were made using a Vantage PRO 2 weather station (Davis Instruments). It was installed according to the manufacturer's recommendations in August 2018 on the roof of the research centre of the Université Bretagne Sud in Lorient (Figure 11). Polystyrene samples were placed at the base of the station.
<figure><img src="image_14.png" /><figcaption>Figure 11. Vantage Pro2 Weather Station.</figcaption></figure>

The rainfall measurement was carried out via a self-draining rain gauge (resolution 0.2 mm; accuracy: ±4%). The temperature was measured with a resolution of 0.1°C and an accuracy of 0.5°C (at 25°C). The measurement of solar radiation was carried out using a precision pyrometer (resolution 1 W/m²; accuracy: ±5%) over the wavelength range between 300 and 1100 nanometres. UV radiation was measured with a precision radiometer (resolution 0.1 MEDs; accuracy: ±8%) over a wavelength range between 290 and 390 nanometres.
Sea temperature measurements were taken using a Water Temp Pro v2 (HOBO) probe. This
probe was placed in the nets containing the samples. The temperature measurements were made
with a resolution of 0.02°C to 25°C and an accuracy of ±0.21°C.

All environmental measurements were performed over a period of one year, from September
2018 to September 2019.

2.3.2. Meteorological conditions

Total rainfall during the study period was 942mm with an average value of 52±40mm/month.

(Figure 12.b). Rainfall is generally higher during the winter period than during the summer period. Thus, the highest rainfall was recorded in December 2018 with 137 mm, and the lowest in July 2019 with only 1 mm.

The average seawater temperature varied between 9°C (in February) and 20°C (in July). The amplitude of the average atmospheric temperatures was between 7°C (in February) and 22°C (in July).

The average minimum solar radiation is recorded in December (93 W/m²) and the average maximum solar radiation in July (601 W/m²) (Figure 12.a). The intensity of UV radiation is minimum in December (1.2*10⁻³ W/m²) and maximum from May to July (3.3 to 3.4*10⁻² W/m²).
<figure><img src="image_15.png" /><figcaption>Figure 12. Measurements of the environmental conditions. A) Measurements of rainfall (mm) and marine and atmospheric temperatures (°C). B) Measurements of solar and UV radiations (W/m²).</figcaption></figure>

## 2.4. Methods

### 2.4.1. Porosity

Porosity is an important parameter for foamed polymers, as it strongly impacts the mechanical properties of the material (e.g. density, compressive strength). To study it, the different samples were cut in the thickness direction. The new surface obtained was gently stamped on an ink pad and then embossed on paper. In this way, the ink stained the cell walls, but not at the bottom of the cells (Figure 13). Three samples were prepared for each type of samples. Observations of the porosity of the samples were then made using a stereomicroscope (Leica MZ16 A). Four images were taken for each of the prepared samples. The 48 images obtained were analysed by the FIJI software (ImageJ).
<figure><img src="image_16.png" /><figcaption>Figure 13. Binocular loupe observation of a polystyrene sample. The pore walls are coloured with a black ink.</figcaption></figure>

For this, the measurement of the surface ($A_i$) of each cell was carried out and the equivalent diameter ($d_i$) of each cell was then calculated (eq. 1). However, at this step only the cells completely included in the mask were measured, while those intersected by the measurement mask are not taken into account in the analysis. Consequently, the larger the cells are, the higher their probability of intersecting the edge of the photography. This means that the population of large cells was underestimated. To overcome this problem, the method for correcting the measuring mask, developed by Miles and Lantuejoul (Avérous et al., 1995) was applied. Thus, the value of the diameter of each object is corrected by the probability of inclusion $P_i$ of the cells in the measurement mask (eq. 2). In this way, the area of the various pores photographed were measured in an automated manner. Then, the number average diameter (dn, µm; eq. 3) was calculated (Julien et al., 2012).

$$d_i = 2\sqrt{\frac{A_i}{\pi}} \quad (\text{Equation 1})$$

$$p_i = \frac{(Z_x - L_x)(Z_y - L_y)}{Z_x Z_y} \quad (\text{Equation 2})$$
$$ \overline{d}_n = \frac{\sum \left( \frac{d_i}{p_i} n_i \right)}{\sum n_i} \quad (Equation 3) $$

### 2.4.2. Measurement of mechanical properties

The compression tests were carried out according to the standard NF EN 826 (Thermal insulating products for building applications — Determination of compression behaviour) and using an electromechanical testing systems (MTS Synergie 1000 RT). For this purpose, five subsamples of each of the samples were manufactured (L*1 = 20*20mm) and stored for 24 hours under controlled atmospheric conditions (T=23±5°C et Rh=50±5%).

To carry out the compression tests the samples were subjected to a preload of 250±10 Pa. The compression speed was 0.1*d/min, where *d* is the thickness of the sample in mm. The compression was carried out until 10% relative deformation was reached. From the curve obtained, the values of compressive strength (GPa), compressive modulus of elasticity (GPa) and yield stress were determined (GPa). In this way, five tests per type of sample were carried out.

### 2.4.3. FTIR

The chemical characterization of samples was enabled using an Attenuated Total Reflection Fourier Transform Infrared spectrometer (ATR-FTIR Vertex70v, Bruker). The spectra were recorded in absorbance mode, in the 4000-600 cm⁻¹ region with 4 cm⁻¹ resolution and 16 scans. Each sample was kept in the germanium diamond cell (ATR Golden Gate) to get a high-quality spectrum. After each ATR-FTIR analysis, the sample holder was cleaned with ethanol.

The carbonyl index (CI) of the samples was calculated (eq. 4).

$$ CI = 1740/694A \quad (Equation 4) $$
This allows to survey the chemical ageing of the material and the formation of carbonyl bonds.

Two other index were proposed: the 1010 index (eq. 5) and the 1637 index (eq. 6).

$$1010I = 1010A/694A \qquad (Equation 5)$$

$$1637I = 1637A/694A \qquad (Equation 6)$$

These both reflect the intensity of the fouling present on the surface of the sample.

## 3. Results

### 3.1. Sample thickness variation

In the case of samples aged in atmospheric conditions, a decrease in sample thickness was observed (Figure 14). Thus, for fish box samples a decrease of 4±1% was observed after one year of ageing. This decrease was much more important for insulation plates with a reduction of 51±3% after one year of ageing. In the case of food trays, the reduction in sample thickness was intermediate with a decrease of 13±1%.

In the case of samples aged in the marine environment, the variations in sample thickness were much smaller. Thus, for fish box samples and insulation plates no significant variation was observed after one year (1.4±1.4% and 4±6.7% respectively). Finally for food trays, a slight increase in thickness was observed over the period November 2018 to July 2019 (10.3±2.3%).
<figure><img src="image_17.png" /><figcaption>Figure 14. Sample thickness variation. CAP: Fish box; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean.</figcaption></figure>

3.2.Evolution of the porosity

For samples aged in air, the variations in average pore diameter are relatively small over the study period (Figure 15). Thus, for fish box, a very slight decrease in mean pore diameter was observed after 12 months of ageing. Thus, over this period the pore diameter decreased from 84±10 µm to 78±16 µm (-7%). In the case of insulation boards, this decrease was more marked with a reduction in the average pore diameter of around 17µm (92±4 µm to 74±3 µm, i.e. -19%). Finally, in the case of food cans, an increase in the average pore diameter was observed with an increase of 23µm on average (74±18 µm to 97±18 µm, i.e. +31%).

In samples aged in the marine environment, the variations in the average pore diameter were very small. For fish box, the variation in pore size after one year of ageing was of the order of 2 µm (84±10 µm to 86±12 µm, i.e. +3%). In the case of insulation plates, the variation in pore diameter after one year of ageing was 4 µm (92±4 µm to 96±12 µm, i.e. +10%). Finally, for food packaging, after 9 months of ageing the variation was around 4 µm (74±18 µm to 78±12 µm, i.e. +4%).
Thus, the analysis of the porosity of the polystyrene samples showed a slightly more marked ageing in the air than in the sea. However, this observation should be put into perspective by the importance of the standard deviations obtained. Thus, only insulation boards aged in a marine environment showed a significant decrease in the average diameter of their pores.

<figure><img src="image_18.png" /><figcaption>Figure 15. Evolution of the number average diameter of the porosity. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean.</figcaption></figure>

### 3.3. Mechanic properties of polystyrene samples

#### 3.3.1. Young's modulus (E)

At T0, the Young's modulus (E) of the samples from the fish boxes averages 4.0±0.5 GPa. In the case of samples aged in the air, the modulus decreases during the first four months (-36%) (Figure 16). The values then remained relatively stable over the next 4 months, before decreasing again. Thus, after one year the Young's modulus of these samples decreased by 52% (1.9±0.3 GPa). In the case of samples aged in the marine environment, the modulus remains relatively constant during the first eight months (-5%). After one year of aging, a decrease in modulus of 47% (2.1±0.5 GPa) was measured.
At T0, the Young's modulus of the samples from the insulation plates was on average 0.5 MPa.
In the case of samples aged in air, during the first four months, the Young's modulus was
multiplied by 4.4 (2.4±0.5 MPa). It then tended to decrease slowly over the next eight months.
Thus, after one year of aging, the Young's modulus reached a value of 1.4±0.6 MPa. In the case
of samples aged in a marine environment, a similar behaviour was observed. Thus, the value of
the modulus was multiplied by about 5 over the first four months (2.7±0.6 MPa). It decreased
thereafter and stabilized around a value of 2.2±0.3 MPa after one year of aging.

At T0, the Young's modulus of the samples from the food trays was on average 1.2±0.3 MPa.
In the case of samples aged in air, during the first four months, the Young's modulus was
multiplied by 7.5 (9.5±1.3 MPa). Despite a slight decrease, the modulus then tended to remain
relatively stable, with a value of 8.1±0.6 MPa after one year of ageing. In the marine
environment, ageing showed a relatively similar behaviour with, however, a clearer decrease in
modulus after four months of ageing. Thus, between the fourth and eighth month of ageing, the
modulus value decreased from 9.3±1.3 to 5.3±2.2 MPa.
<figure><img src="image_19.png" /><figcaption>Figure 16. Evolution the ratio of the Young's modulus (E) and its initial value (Ei) for the different samples. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean.</figcaption></figure>

3.3.2. Compressive strength (Rs)

At T0, the compressive strength (Rs) of the samples from the fish crates averaged 127.7±1.4 MPa (Figure 17). For samples aged in air, the compressive strength remained relatively constant for one year. Thus, after 12 months of ageing, the value of the compressive strength of the samples was on average 124.1±4.2 MPa. In the case of samples aged in a marine environment, the compressive strength was more variable over time. Indeed, if the compression values remained relatively constant for the first eight months, but after one year of ageing a decrease was measured (-21%; 107.9±13.9 MPa).

At T0, the compressive strength of the insulation plates averaged 166.2±19.8 MPa. The inter-sample variability in compressive strength was relatively high compared to the fish box samples. In the case of samples aged in the air during the first four months, the variation in compressive strength was not significant (153.0±43 MPa). The Rs value decreased sharply over the following four months. Thus, after eight months of ageing, Rs reached a value of 56.9±12.1
MPa. This value remained relatively constant thereafter (60.4±32.4 MPa; -64% compared to the initial value). In the case of samples aged in a marine environment, a less abrupt decrease in compressive strength was measured. Thus, the *Rs* value decreased by 13% on average over the first four months (144.4±78.8 MPa). However, the variability of the measurements made this decrease not very significant. After eight months of ageing, the *Rs* value was 107.9±55.5 MPa. Finally, after one year of ageing, the *Rs* value was 79.9±49.2 MPa (-52%).

At T0, the compressive strength of the food trays averaged 57.6±79.1 MPa. Thus, from the non-aged state, the measurements showed a strong variability from one sample to another. In the case of the samples aged in air, the *Rs* value increased continuously during the experiment. Thus, after four months, the mean *Rs* value was multiplied by about four (201.6±66.3 MPa). It then reached 279.4±202.9 MPa after eight years of ageing, and 568.8±251.9 MPa after one year of ageing (i.e. a value multiplied by about 10 with respect to the initial value).

In the marine environment, ageing showed a relatively similar behaviour. Thus, the value of *Rs* increased from the fourth month of ageing (166.4±206.3 MPa), the variability of the measurements here being very high. Around eight months of ageing the mean value of *Rs* was 436.4±228.0 MPa, i.e. a multiplication by about 8 of its value compared to the initial value.
<figure><img src="image_20.png" /></figure>

Figure 17. Evolution of the ratio of the compressive strength (Rs) and its initial value (Rs_i) for the different samples. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean.

## 3.4. FTIR Index

### 3.4.1. Carbonyl index (CI)

In air, the carbonyl index of the different samples tends to increase (Figure 18). Thus, for fish boxes, the *CI* was multiplied by about 3 (3.1±0.1) in 10 months, before marking a decrease at the twelfth month (2.5±0.1). However, this increase in the carbonyl index was relatively small in the first six months (September to March), and was more marked between April and July (months 7 to 10). In the case of isolation plates, the increase in carbonyl index reached its maximum in July (3.1±0.1), then decreased in September (2.4±0.1). Finally, for food trays, the carbonyl index was stable for the first four months (1.0±0.0 in January). It then increased steadily and reached 2.9±0.0 in September.

In the marine environment, the carbonyl index behaved differently and showed more variability than in air-aged samples. In the case of fish crates, the *CI* increased during the first 4 months (2.8±0.3 in January) and then decreased, fluctuating between 1.4 and 1.8 during the summer
period. For insulation boards, the CI also increased during the first 4 months (2.8±0.2 in January) and then decreased to 0.2±0.3 in September. Finally, the CI of food trays followed a relatively similar pattern: an increase in the first four months (2.3±0.0 in January), then a decrease between January and March (1.4±0.1). Finally, between March and July the CI values remained relatively stable (between 1.6 and 1.8).

<figure><img src="image_21.png" /><figcaption>Figure 18. Evolution of the Carbonyl Index of the samples. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean.</figcaption></figure>

3.4.2. 1010I

In the atmosphere, the 1010 index of the different samples increased relatively steadily during the first ten months, and then decreased slightly (Figure 19). Thus, for fish crates, the 1010I was multiplied by about 3 (3.0±0.1) in 10 months, before marking a slight decrease at the twelfth month (2.6±0.5). In the case of insulation plates, the increase in 1010I peaked in July (3.3±0.1) and then decreased in September (2.4±0.1). Finally, for food trays, the 1010I increased steadily and reached 3.0±0.2 in July, before decreasing slightly in September (2.9±0.0).
In the marine environment, the 1010I increased much more strongly and showed more variability than for air-aged samples. In the case of fish crates, the value of 1010I increased strongly especially at the end of the summer period (12.9±6.2). For insulation plates, the 1010I also increased during the first 10 months (10.7±1.3 in July), then decreased to 6.0±1.1 in September. Finally, the 1010I of the food trays increased throughout the period for which samples were available and reached 12.1±2.9 in July.

<figure><img src="image_22.png" /><figcaption>Figure 19. Evolution of the 1010 Index of the samples. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean.</figcaption></figure>

3.4.3. 1637I

In the atmosphere, the 1637 index of the different samples increased relatively regularly during the first ten months of study before generally a decrease in September (Figure 20). Thus, for fish boxes, 1637I was multiplied by about 2 (2.1±0.1) in the space of 10 months, before a slight decrease in the twelfth month (1.8±0.2). In the case of insulation plates, the increase in 1637I reached its maximum in July (2.9±0.1), then decreased in September (2.0±0.1). Finally, for
food trays, the 1010I increased steadily and reached 1.9±0.1 in July and was maintained thereafter (2.0±0.0).

In the marine environment, 1637I increased more strongly and showed more variability than for samples aged in the air. In the case of fish crates, the value of 1637I increased strongly especially during the summer period (5.0±1.9). For insulation plates, the 1637I also increased during the 12 months of the study (4.1±0.4 in September). Finally, the 1637I of the food trays increased throughout the period for which samples were available and reaches 5.1±0.5 in July.

<figure><img src="image_23.png" /><figcaption>Figure 20. Evolution of the 1637 Index of the samples. CAP: Fish crate; ISOL: Insulation plate; KBB: Food packaging; r: roof; o: ocean.</figcaption></figure>

# 4. Synthesis

## 4.1. Marine ageing versus atmospheric ageing

The ageing of the samples resulted in different trends depending on the analysis, and the Carbonyl Index seems to be the most sensitive indicator to quickly highlight ageing in the air. His study highlighted two important points. Firstly, the intensity of the CI is probably correlated with parameters linked to seasonality and more particularly the cumulative intensity of solar
radiation and cumulative rainfall. However, the ageing mechanisms may not be quite the same from one sample to another. The present study does not allow us to specify whether these differences are related to the type of polystyrene foam (XPS vs. EPS), or have different additives from one sample to another. This is one of the main disadvantages of working with objects whose manufacturing process is not known to the researchers.

Chemical ageing is greatly slowed down when samples are immersed in the marine environment. Immersion offers good protection against U.V. rays. Fouling, whether organic or inorganic, is however much more important for samples aged at sea.

It should be noted, however, that a similar behaviour is generally observed for the same material during marine and air ageing. The amplitude of the modifications is generally greater in the air environment than in the marine environment. This opens up the possibility of proposing an approximate prediction of ageing in the marine environment based on observations made in the atmospheric environment.

## 4.2. Duration of the study

With regard to the thickness of the samples and the evolution of their porosity, few differences were observed between the beginning and the end of the study for most of the tests carried out. Thus, the study time (one year) seems too short to be able to clearly show the ageing of the polystyrene according to these parameters. Furthermore, the great variability of the results obtained for the same environment and for a given period of time means that it is often impossible to highlight a statistically significant variation. The only exception that can be noted is for insulation plates aged in an atmospheric environment and which show for these both parameters a clear ageing with a loss of its structural properties.
## 4.3. *Differences between materials*

The results obtained on the mechanical behaviour of the different materials make it possible to highlight very different behaviour from one foamed polystyrene to another. Indeed, some foamed PS gain in resistance to compression while others, on the contrary, lose their compressive strength. However, the variability of the results obtained is often very significant within the same material, which limits the ability to determine variations that are statistically significant.

It is therefore difficult at this stage to predict the behaviour of the material from its XPS/EPS nature. It is also difficult to predict the behaviour of foamed polystyrene based on its characteristics at T0.

## 5. Conclusion

Given the lack of data on the ageing of polystyrene in the marine environment, it was essential to acquire them first. For this purpose, different materials proposed by the OceanWise consortium were tested by our research team. Due to their low density, EPS float on the surface of the sea. They therefore combine both strictly aerial and strictly marine ageing. The air ageing results in a degradation of the polystyrene under the action of solar radiation. Conversely, the submerged side undergoes less ageing. The exact action of the biofouling remains to be clarified since it can both play a protective role (e.g. algae protecting the EPS from the sun's rays), but can also be an agent of degradation (e.g. crabs attacking the samples). Furthermore, different degradation behaviours were observed between the three objects tested, thus highlighting the impact of factors internal to the polymer (e.g. shape, additives). Thus, the data obtained will provide the basis for a better evaluation of the new materials proposed as an alternative to polystyrene foam.
6. Supplementary materials

6.1. Mechanic properties of polystyrene samples

6.1.1. Young's modulus (E, GPa)

<table><caption>Table 1. Young's modulus (E, GPa)</caption><thead><tr><th>Ageing environments</th><th>Samples</th><th></th><th>T0</th><th>T4</th><th>T8</th><th>T12</th></tr></thead><tbody><tr><td rowspan="6">Roof environment</td><td rowspan="2">CAP</td><td>Mean</td><td>4.0</td><td>2.5</td><td>2.7</td><td>1.9</td></tr><tr><td>Standard deviation</td><td>0.5</td><td>0.7</td><td>0.3</td><td>0.3</td></tr><tr><td rowspan="2">ISOL</td><td>Mean</td><td>0.5</td><td>2.4</td><td>1.7</td><td>1.4</td></tr><tr><td>Standard deviation</td><td>0.1</td><td>0.5</td><td>0.1</td><td>0.6</td></tr><tr><td rowspan="2">KBB</td><td>Mean</td><td>1.3</td><td>9.4</td><td>7.9</td><td>8.1</td></tr><tr><td>Standard deviation</td><td>0.4</td><td>1.3</td><td>0.8</td><td>0.6</td></tr><tr><td rowspan="6">Marine environment</td><td rowspan="2">CAP</td><td>Mean</td><td>4.0</td><td>3.7</td><td>3.8</td><td>2.1</td></tr><tr><td>Standard deviation</td><td>0.5</td><td>0.1</td><td>0.1</td><td>0.5</td></tr><tr><td rowspan="2">ISOL</td><td>Mean</td><td>0.5</td><td>2.7</td><td>2.1</td><td>2.3</td></tr><tr><td>Standard deviation</td><td>0.1</td><td>0.7</td><td>0.6</td><td>0.3</td></tr><tr><td rowspan="2">KBB</td><td>Mean</td><td>1.3</td><td>9.2</td><td>5.3</td><td></td></tr><tr><td>Standard deviation</td><td>0.4</td><td>1.3</td><td>2.2</td><td></td></tr></tbody></table>
6.1.2. Compressive strength (Rs, kPa)

<table><caption>Table 2. Compressive strength (Rs, kPa)</caption><thead><tr><th>Ageing environments</th><th>Samples</th><th></th><th>T0</th><th>T4</th><th>T8</th><th>T12</th></tr></thead><tbody><tr><td rowspan="8">Roof environment</td><td rowspan="2">CAP</td><td>Mean</td><td>127.7</td><td>124.2</td><td>133.7</td><td>124.1</td></tr><tr><td>Standard deviation</td><td>1.4</td><td>4.7</td><td>2.5</td><td>4.2</td></tr><tr><td rowspan="2">ISOL</td><td>Mean</td><td>166.2</td><td>153.0</td><td>56.9</td><td>60.4</td></tr><tr><td>Standard deviation</td><td>19.8</td><td>43.2</td><td>12.1</td><td>32.4</td></tr><tr><td rowspan="2">KBB</td><td>Mean</td><td>57.6</td><td>201.6</td><td>279.1</td><td>568.8</td></tr><tr><td>Standard deviation</td><td>79.1</td><td>66.3</td><td>202.9</td><td>51.9</td></tr><tr><td rowspan="8">Marine environment</td><td rowspan="2">CAP</td><td>Mean</td><td>127.7</td><td>124.0</td><td>131.8</td><td>100.9</td></tr><tr><td>Standard deviation</td><td>1.4</td><td>3.4</td><td>2.6</td><td>13.9</td></tr><tr><td rowspan="2">ISOL</td><td>Mean</td><td>166.2</td><td>144.4</td><td>107.9</td><td>79.9</td></tr><tr><td>Standard deviation</td><td>19.8</td><td>78.8</td><td>55.5</td><td>49.2</td></tr><tr><td rowspan="2">KBB</td><td>Mean</td><td>57.6</td><td>166.4</td><td>436.4</td><td></td></tr><tr><td>Standard deviation</td><td>79.1</td><td>206.3</td><td>228.0</td><td></td></tr></tbody></table>
6.2. FTIR indexes

<table><caption>Table 3. FTIR indexes.</caption><thead><tr><th></th><th>Samples</th><th></th><th>0</th><th>2</th><th>4</th><th>6</th><th>8</th><th>10</th><th>12</th></tr></thead><tbody><tr><td rowspan="12">Roof environment</td><td rowspan="6">CAP</td><td>Mean CI</td><td>1,0</td><td>1,2</td><td>1,5</td><td>1,5</td><td>2,2</td><td>3,1</td><td>2,5</td></tr><tr><td>SD CI</td><td>0,1</td><td>0,0</td><td>0,1</td><td>0,0</td><td>0,1</td><td>0,1</td><td>0,1</td></tr><tr><td>Mean FIc</td><td>1,0</td><td>1,4</td><td>1,6</td><td>1,6</td><td>2,2</td><td>3,0</td><td>2,6</td></tr><tr><td>SD Fic</td><td>0,2</td><td>0,1</td><td>0,1</td><td>0,1</td><td>0,1</td><td>0,1</td><td>0,5</td></tr><tr><td>Mean Fio</td><td>1,0</td><td>0,9</td><td>1,0</td><td>1,0</td><td>1,5</td><td>2,1</td><td>1,8</td></tr><tr><td>SD Fio</td><td>0,2</td><td>0,0</td><td>0,1</td><td>0,0</td><td>0,0</td><td>0,1</td><td>0,2</td></tr><tr><td rowspan="6">ISOL</td><td>Mean CI</td><td>1,0</td><td>1,4</td><td>1,3</td><td>1,8</td><td>2,0</td><td>3,1</td><td>2,4</td></tr><tr><td>SD CI</td><td>0,0</td><td>0,1</td><td>0,1</td><td>0,2</td><td>0,4</td><td>0,1</td><td>0,1</td></tr><tr><td>Mean FIc</td><td>1,0</td><td>1,4</td><td>1,5</td><td>2,0</td><td>1,8</td><td>3,3</td><td>2,4</td></tr><tr><td>SD Fic</td><td>0,0</td><td>0,1</td><td>0,2</td><td>0,3</td><td>0,3</td><td>0,1</td><td>0,1</td></tr><tr><td>Mean Fio</td><td>1,0</td><td>1,3</td><td>1,3</td><td>1,6</td><td>1,6</td><td>2,9</td><td>2,0</td></tr><tr><td>SD Fio</td><td>0,1</td><td>0,1</td><td>0,2</td><td>0,2</td><td>0,3</td><td>0,1</td><td>0,1</td></tr><tr><td rowspan="6">KBB</td><td>Mean CI</td><td>1,0</td><td>1,0</td><td>1,0</td><td>1,8</td><td>2,3</td><td>2,7</td><td>2,9</td></tr><tr><td>SD CI</td><td>0,1</td><td>0,1</td><td>0,0</td><td>0,0</td><td>0,1</td><td>0,1</td><td>0,0</td></tr><tr><td>Mean FIc</td><td>1,0</td><td>1,7</td><td>1,5</td><td>2,4</td><td>2,8</td><td>3,0</td><td>2,9</td></tr><tr><td>SD Fic</td><td>0,2</td><td>0,3</td><td>0,1</td><td>0,5</td><td>0,6</td><td>0,2</td><td>0,0</td></tr><tr><td>Mean Fio</td><td>1,0</td><td>0,9</td><td>0,8</td><td>1,4</td><td>1,6</td><td>1,9</td><td>2,0</td></tr><tr><td>SD Fio</td><td>0,2</td><td>0,2</td><td>0,0</td><td>0,2</td><td>0,1</td><td>0,1</td><td>0,0</td></tr><tr><td rowspan="3">Marine environment</td><td rowspan="3">CAP</td><td>Mean CI</td><td>1,0</td><td>2,0</td><td>2,8</td><td>0,6</td><td>1,9</td><td>1,5</td><td>1,9</td></tr><tr><td>SD CI</td><td>0,1</td><td>0,1</td><td>0,3</td><td>0,1</td><td>0,4</td><td>0,2</td><td>0,5</td></tr><tr><td>Mean FIc</td><td>1,0</td><td>2,6</td><td>4,4</td><td>3,8</td><td>5,6</td><td>6,1</td><td>12,9</td></tr></tbody></table>
PART 1. EPS and XPS ageing in the natural environment

<table><tbody><tr><td></td><td>SD Fic</td><td>0,2</td><td>0,2</td><td>0,5</td><td>0,7</td><td>2,3</td><td>0,7</td><td>6,2</td></tr><tr><td></td><td>Mean Fio</td><td>1,0</td><td>1,7</td><td>2,5</td><td>2,3</td><td>2,7</td><td>3,7</td><td>5,0</td></tr><tr><td></td><td>SD Fio</td><td>0,2</td><td>0,1</td><td>0,2</td><td>0,4</td><td>0,7</td><td>0,7</td><td>1,9</td></tr><tr><td rowspan="6">ISOL</td><td>Mean CI</td><td>1,0</td><td>2,1</td><td>2,3</td><td>1,4</td><td>1,5</td><td>1,4</td><td>0,2</td></tr><tr><td>SD CI</td><td>0,0</td><td>0,1</td><td>0,2</td><td>0,1</td><td>0,1</td><td>0,1</td><td>0,2</td></tr><tr><td>Mean FIc</td><td>1,0</td><td>2,7</td><td>2,9</td><td>5,6</td><td>6,1</td><td>10,7</td><td>6,0</td></tr><tr><td>SD Fic</td><td>0,0</td><td>0,3</td><td>0,1</td><td>1,7</td><td>1,0</td><td>1,3</td><td>1,1</td></tr><tr><td>Mean Fio</td><td>1,0</td><td>2,1</td><td>2,2</td><td>3,2</td><td>3,5</td><td>3,7</td><td>4,1</td></tr><tr><td>SD Fio</td><td>0,1</td><td>0,2</td><td>0,1</td><td>0,5</td><td>0,1</td><td>0,2</td><td>0,4</td></tr><tr><td rowspan="6">KBB</td><td>Mean CI</td><td>1,0</td><td>1,9</td><td>2,3</td><td>1,7</td><td>1,7</td><td>1,9</td><td></td></tr><tr><td>SD CI</td><td>0,1</td><td>0,1</td><td>0,0</td><td>0,1</td><td>0,4</td><td>0,2</td><td></td></tr><tr><td>Mean FIc</td><td>1,0</td><td>2,4</td><td>3,0</td><td>5,4</td><td>7,0</td><td>12,1</td><td></td></tr><tr><td>SD Fic</td><td>0,2</td><td>0,2</td><td>0,2</td><td>1,6</td><td>4,8</td><td>2,9</td><td></td></tr><tr><td>Mean Fio</td><td>1,0</td><td>1,5</td><td>2,0</td><td>2,9</td><td>2,8</td><td>5,1</td><td></td></tr><tr><td>SD Fio</td><td>0,2</td><td>0,1</td><td>0,0</td><td>0,5</td><td>1,0</td><td>0,5</td><td></td></tr></tbody></table>
PART 2. Accelerated mechanical abrasion of Expanded Polystyrene

Maïwenn Le Gallª, Gwénaël Le Maguerᵇ, Stéphane Bruzaudª, Mikaël Kedzierskiª

**Abstract**

Expanded polystyrene is a massively used plastic for packaging and insulation. This is why objects made from expanded polystyrene are among the top ten marine litter found on European beaches. In this context, the OceanWise project aims to propose a set of measures to reduce the impact of products made from EPS in the North-East Atlantic. In this project, accelerated mechanical abrasion has been studied for three types of EPS in the case of abrasion with dry sand and with sand and sea water. The dimensions and weight of the samples were recorded every 24 hours and microscopic observations were made on the samples at different stages of ageing. The results highlighted the influence of the type of environment and the size of the sand on the degradation of the polystyrene.

**Keywords**

Expanded Polystyrene, Mechanical abrasion, Accelerated aging, Microplastics, Microscopy
observation

<footnote>ª IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France</footnote>

<footnote>ᵇ Archipel institute, Université Bretagne Sud, 56100 Lorient, France</footnote>
# 1. Introduction

Various types of waste are present in the oceans: plastics, glass, ceramics or even metals. Due to the global consumption of polymers, plastic materials have become the main waste found in the marine environment. Problems associated with plastic materials have been reported since the 1970s (Xanthos and Walker, 2017). In Europe, despite the increase in the recycling rate since 2010, plastics waste management remains relatively poor (PlasticsEurope, 2018). A study conducted by the National Center for Ecological Analysis and Synthesis (NCEAS) at the University of Santa Barbara quantified the input of plastic waste from land to the ocean at 8 million tonnes (Jambeck et al., 2015). This plastic waste is not neutral for the environment and can, for example, have consequences for living beings. More than 700 species of marine organisms, including mammals, interact with plastic debris (Thompson, 2017). One of the most worrying aspects is the presence of microplastics, i.e. particles less than 5 mm in size, in the oceans. These microplastics result from the abrasion and degradation of plastic waste, favoured by light and oxygen, which can end up being ingested by marine organisms (ter Halle et al., 2017).

Foam plastic products made from expanded polystyrene are among the top ten marine litter found on European beaches. Expanded polystyrene (EPS) is a type of plastic widely used for packaging and insulation. The various properties of EPS explain its very wide use in the industrial world. EPS has a very low density (27.5 kg/m³), low manufacturing cost and also has very good insulating and mechanical properties (SEABIRD, 2019). These properties make it one of the most important materials in the construction industry. EPS is used in the majority of single-use food containers such as fish and meat trays. Nevertheless, this massive use of EPS has consequences for the environment. Although EPS is recyclable, it is rarely recyclable, due to its contamination by food or because of the low cost-effectiveness of transporting and recycling. As a result, it is most often recovered as energy or disposed of in landfill sites.
However, due to its light weight, EPS is easily blown away from bins and landfills (SEABIRD, 2019).

EPS is not biodegradable and tends to fragment, with small fragments being able to travel long distances. Thus, the degradation of EPS can occur in different marine environments, from the beach to the ocean. Different mechanisms interact with the polymer at different scales; there is physical and chemical degradation. The degradation mechanisms of a plastic in a natural environment are difficult to predict and understand. Several mechanisms intervene simultaneously on the material and at different rates when it ends up in a marine environment. When the material ends up on the surface of the water at low temperature, the degradation of the material will be slow. Photo-oxidation, water absorption and swelling may occur. When the material is left on a beach, a faster degradation is observed, the EPS will mainly undergo photo-oxidation and mechanical abrasion (Shim et al., 2014). Photo-oxidation is a well-studied mechanism, occurring first on the polymer when it ends up on the coast. The photodegradation mechanism occurs due to chain split phenomena. Yellowing of the exposed surface of the EPS was observed by Anthony Andrady et al (Andrady and Pegram, 1991). In the end, the specimen becomes brittle and crumbles into small fragments, which is consistent with a loss of mechanical properties caused by photo-oxidation. Unlike photo-oxidation, mechanical abrasion is not yet well understood. Few scientists have worked on the subject, Won Joon Shim et al. have conducted experiments to understand whether accelerated mechanical abrasion of large plastics can produce micrometer-sized plastics (Shim et al., 2014). They demonstrated the production via abrasion of a large number of EPS particles between 0.75 and 500 µm in size.

This study has for objective to well understand the mechanism abrasion in marine environment. Accelerated mechanical abrasion is carried out in glass bottles in rotation for 10 days in two different types of environment. One recreated the abrasion on a beach with only sand contained in glass bottles, and the other one recreated the edge of the water surface with a blend of
saltwater and sands. The sand was sifting to measure the influence of the sand size of the degradation of the material. After the accelerated aging, microscopy observations were carried out to observe the surface degradation and eventual degradation inside the EPS. Furthermore, extraction of microplastics contained in the sand use during the experiment was to proceed. Microplastics will be identified thanks to Fourier Transform Infrared (FT-IR). In this context, the aim of our study is to better understand the ageing mechanisms of different polystyrene foams undergoing an abrasion process similar to what they may undergo on a beach.

## 2. Materials and methods

### 2.1. *Samples*

The three EPS foams were obtained from food boxes (KBB), insulation plates (ISOL) and fish crates (CP). Rectangular samples of approx. 20 mm × 30 mm were cut manually (Table 4).

<table><caption>Table 4. Dimensions of the samples</caption><thead><tr><th>Origin</th><th>Name</th><th>Dimension<br>(L*W*T) (mm)</th></tr></thead><tbody><tr><td>Insulation<br>plates</td><td>ISOL</td><td>30*20*3</td></tr><tr><td>Lunch boxes</td><td>KBB</td><td>30*20*2.5</td></tr><tr><td>Seafood boxes</td><td>CP</td><td>30*20*18</td></tr></tbody></table>

### 2.2. *Experimental conditions*

Accelerated ageing by mechanical abrasion was carried out in rotating glass bottles for 10 days. The sand used in the study was previously sieved according to different diameters: 2 mm, 1 mm, 500 µm, 250 µm and 125 µm. The organic particles and possible microplastics contained
in the sands were removed using a saturated salt solution. Three samples of each EPS were placed in glass bottles with sands of different sizes. The rotation speed of the bottles was 65 rpm. The samples were weighed and their length, width and thickness were measured every 24 hours for 10 days. Two different environments were tested, one being dry sand and the other a mixture of sand and a 30 g/L salt water solution.

### 2.3. Microscopy observation

Binocular microscope was used to the surface analyses and the evolution of the porosity of the EPS samples.

## 3. Results and discussion

### 3.1. Weight variation

The variations in sample weight as a function of the diameter of the sand particles are shown in figure 16 (Figure 21).

In the case of abrasion with dry sand, similar trends were observed for EPS samples from food boxes and insulation plates (fig.16a and c). Thus, a significant increase in mass after 24 hours of abrasion was observed when sand with a grain size between 125 and 500 µm in diameter was used. In this context, the mass of the samples increased by 175 to 200% in 24 hours. A smaller increase, of the order of 125% was shown for fish box samples abraded with these sand grain sizes (fig.16e). Beyond these first 24 hours, and for these ranges of sand grain sizes, the mass of the samples remains stable until the experiment was stopped. For the sand range [0.5-1]mm, a smaller increase than with the finer sand ranges was observed over the first 48 hours. Then, a stability or even a slight decrease in mass was noted. In the case of abrasion tests with coarser sands (>1 mm), a different behaviour was shown. First of all, no increase in mass could be noted over the first few hours of abrasion. On the other hand, a decrease in mass was clearly
shown. This decrease in mass was relatively linear, of the order of 3%/24 hours for insulation boards and food boxes. In the case of fish boxes, this reduction was much more modest.

This increase in mass during the abrasion process is counter-intuitive, but is easily explained by the incorporation of sand grain in the polystyrene in the first few hours of the tests. It is not possible to relate the initial porosity size to the amount of sand incorporated. For example, insulation boards showed a very large increase, while for fish crates the increase was much more modest. Both materials had similar average porosity (approx. 160 to 170 µm). It should also be noted that they were both EPS and therefore nature (XPS versus EPS) does not seem to be an explanatory factor. It should be noted, however, that the observation of the spaces between the beads of polystyrene showed that they were often filled with sand, which sometimes penetrated far into the core of the tested materials.

For example, finer sand tends to easily infiltrate polystyrene foam and thus increase its density. Coarser sand, on the other hand, leads to accelerated degradation.

The observation of the samples in the case of abrasion tests with a mixture of sand plus seawater showed a different evolution in the mass of the samples. Indeed, this increase over time was observed in all cases. It was more or less rapid and was often accompanied by a more or less clear plateau learned after approximately 24 to 96 hours of testing. The variability in the behaviour of the samples is also greater than in the case of abrasion with dry sand.

This increase in mass was due to the absorption of water by the polystyrene foams, as well as the penetration of the sand grains. As the samples partly float on the surface of the water due to their low density, the degradation was significantly slowed down. In addition, the formation of scum during the experiments should be noted. The samples seemed to be incorporated into the scum, which protected them from abrasion. The formation of scum on the seashore is a common
PART 2. Accelerated mechanical abrasion of Expanded Polystyrene

phenomenon, especially in winter. This could therefore be a factor which, by reducing the abrasive action of the sand, locally reduces the ageing rate of the plastic waste.

<figure><img src="image_24.png" /><figcaption>Figure 21. Mass variations of the samples as a function of time and size range of the sand particles, and for dry and wet environments.
The average pore diameter (dw) measured by microscopy is also indicated.</figcaption></figure>
3.2. *Variation of dimensions*

As with the mass of the samples, the dimensions of the samples were checked every 24 hours.

In this way it is possible to calculate variations in the volume of the samples (Figure 22).

As with the weight variation, the volume initially increased in the case of abrasion tests with
fine sand for insulation board and food box samples. These results were consistent with the
mass variation results. The infiltration of sand into the material seemed to generate a swelling
of the samples or a geometrical modification of the cell and tended to increase the volume of
the samples. After 24 to 96h, a decrease in thickness was observed for samples abraded with
sand with a grain size greater than 500 µm. This decrease was all the more important as the
sand grain size is important. For example, a reduction of only a few percent was observed for
samples abraded with sand between 500 µm and 2 mm. On the other hand, a decrease of 40%
was observed for KBB and ISOL samples abraded with sand larger than 2 mm.

In the case of fish boxes, a different trend from that observed for the other two types of polystyrene was highlighted. Indeed, a decrease in thickness was observed after only 24 hours of abrasion and for all sand size ranges. However, the 125 and 250 µm sands had a minor effect on volume reduction compared to the larger size ranges. Thus, after 10 days, a 10% decrease in volume was identified for sand size ranges between 125 and 500 µm, while a 25% decrease in volume was observed for sand with a grain size greater than 2 mm.

These observations underline once again the influence of the sand diameter on the ageing rate
of foamed polystyrene: this implies that the type of beach and the grain size of the sand will
have an impact on the ageing of the foamed polystyrene waste that will be deposited.
Furthermore, the significant decrease in the average porosity for all the samples shows that the
reduction in volume is due to both surface abrasion and compaction. The latter is very important
near the edges of the samples, but is also evident at the heart of the material.
In the case of abrasion tests in a mixture of salt water and sand, and for all types of samples, there is a slight decrease in volume. This suggests that the sand does not penetrate the polystyrene foams as effectively and therefore does not vary the volume positively. For insulation plate and food box samples, the size of the sand seems to have less influence on the rate of degradation. After 10 days a decrease of 5 to 20% in volume is observed. On the contrary, the influence of the grain size was very clear in the case of the fish box samples: the higher the grain size, the greater the reduction in volume. The volume reduction pattern is very similar to that observed in the case of abrasion with dry sand.
PART 2. Accelerated mechanical abrasion of Expanded Polystyrene

<figure><img src="image_25.png" /><figcaption>Figure 22. Volume variations of the samples as a function of time and size range of the sand particles, and for dry and wet environments.
The average pore diameter (dw) measured by microscopy is also indicated.</figcaption></figure>

3.3. Microscopy observations

The observations carried out allow the comparison of the impact of the sand on the tested
samples.

The figure below shows the surface of the insulation board samples after a 10-day accelerated
mechanical abrasion test and for different sand sizes (Figure 23). Whatever the sand grain size,
changes in the surface condition were observed. For example, the edges of the samples are rounded. A change in colour was also observed, particularly in the case of abrasion with sand with a diameter greater than 2 mm. In addition, the presence of sand was identified on the surface of the samples contained in sands 500, 250 and 125 µm, confirming the infiltration of sand into the samples and their weight gain. Similar observations were found on the surface of the two other kind of samples.

<figure><img src="image_26.png" /><figcaption>Figure 23. Microscopic observation of an insulation plate sample aged with dry sand.</figcaption></figure>
The figure below shows a section of the inside of a sample insulation board after 10 days ageing in dry sand (125-250µm). Figure 7.a shows a compression waves at the edge of the sample, which indicated mechanical stress on the material. In addition, an increase in cell density was observed at the edges of the specimens, indicating compression of the material. The material was mechanically compressed when the specimen is subjected to impact during abrasion. This observation was observed in all cases and explains the medium-term decrease in the volume of the samples. This implies that in the natural environment, wind and waves are likely to cause the samples to compress. The action of U.V. rays, which tends to reduce the mechanical resistance of polystyrene foams, would therefore act in the natural environment in synergy with these ageing factors. The direct abrasion by the sand would therefore be relatively low in the end.

Figure 7.b shows the penetration of sand into the sample. This observation explains the weight gain of the samples in sand of grain size 125 µm. Fine sand has the ability to pass through the space between the PS beads and penetrate into the polystyrene foams. In addition, sand was identified all along the edges of the sample. This incorporation of sand at the periphery of the samples contributes to the increase of their mass.

<figure><img src="image_27.png" /><figcaption>Figure 24. Microscopic observation of the isolation EPS after accelerated degradation in dry environment (125µm sand).</figcaption></figure>
Observation of the surface of samples aged in the water/sand mixture shows similar degradation characteristics on their surface such as colour changes due to the incorporation of sand into the surface. However, the sand did not penetrate much into the samples. Due to the formation of scum and the excellent flotation capacity on the surface of the water from the samples, the latter were necessarily less in contact with the sand. In addition, wet sand has a more cohesive behaviour which also limited its ability to enter the material. Finally, while the area of high compression of porosity can be observed around the periphery of all samples and in all configurations tested, it remained less pronounced than in the abrasion tests with dry sand.

4. **Conclusion**

In this study, the accelerated mechanical abrasion of three different types of polystyrene foam was analysed in two different contexts, the first with dry sand and the second in a mixture of sand and sea water. The results showed that the intensity of material degradation was a function of various factors including the size of the sand grains used. Thus, the coarser the sand grains, the faster the degradation. The finer the sand grains appear to have less impact, but penetrated the material and contributes to increasing its mass. Nevertheless, even with a doubling of this the flotation of the polystyrene is very little affected. Thus, it is possible to hypothesise that the characteristics of the beach where the expanded polystyrene runs aground have an influence on its degradation. However, it should be noted that in water, polystyrene floats even in very thin layers of liquid. The material is not in contact with the sand to any great extent and degradation is therefore slowed down. In addition, the presence of scum helps to protect the material from degradation.

All the shocks suffered by polystyrene foam combined with the action of U.V. rays contribute to its flattening. Although no significant fragmentation phenomenon has been demonstrated in experiments, on a smaller scale, abrasion contributes to the generation of microplastics. Observations in Fourier Transform Infrared Spectroscopy (FT-IR) have already confirmed the
presence of polystyrene in the sand used in the tests, but tests to characterise the quantities and
size distributions of the microplastics generated during accelerated ageing could not be carried
out due to a technical problem.

Finally, the mechanical characteristics must now be related to the results of this study. Indeed,
the behaviour observed during the study does not seem to be correlated with the nature of the
foam (expanded/extruded), nor with the size of the porosity.
References

Andrady, A.L., Pegram, J.E., 1991. Weathering of polystyrene foam on exposure in air and in seawater. J. Appl. Polym. Sci. 42, 1589-1596. https://doi.org/doi:10.1002/app.1991.070420612

Jambeck, J.R., Geyer, R., Wilcox, C., Siegler, T.R., Perryman, M., Andrady, A., Narayan, R., Law, K.L., 2015. Marine pollution. Plastic waste inputs from land into the ocean. Science (80-. ). 347, 768-771. https://doi.org/10.1126/science.1260352

PlasticsEurope, 2018. Plastics - the Facts 2018.

SeaBird, 2019. OCEANWISE WP5 : State of art and suppliers report.

Shim, W.J., Song, Y.K., Hong, S.H., Jang, M., Han, G.M., Won Jung, S., 2014. Producing fragmented micro- and nano-plastics from expanded polystyrene with an accelerated mechanical abrasion experiment, in: Abstract Book 24th Annual Meeting SETAC. SETAC, Pensacola, FL.

ter Halle, A., Ladirat, L., Martignac, M., Mingotaud, A.F., Boyron, O., Perez, E., 2017. To what extent are microplastics from the open ocean weathered? Environ. Pollut. 227, 167-174. https://doi.org/https://doi.org/10.1016/j.envpol.2017.04.051

Thompson, R.C., 2017. Future of the sea: plastic pollution. A report examining the trends and implications of plastic pollution in the sea.

Xanthos, D., Walker, T.R., 2017. International policies to reduce plastic marine pollution from single-use plastics (plastic bags and microbeads): A review. Mar. Pollut. Bull. 118, 17-26. https://doi.org/https://doi.org/10.1016/j.marpolbul.2017.02.048
**PART 3. Microplastic contamination of packaged meat: occurrence and associated risks**

Mikaël Kedzierski<sup>a*</sup>, Benjamin Lechat<sup>a</sup>, Olivier Sire<sup>b</sup>, Gwénaël Le Maguer<sup>c</sup>, Véronique Le Tilly<sup>b</sup>, Stéphane Bruzaud<sup>a</sup>

**Abstract**

Food trays are often made from extruded polystyrene (XPS), and quantities of millimetre-sized particles of this material are trapped between the meat they contain and the sealing film. The purpose of this study is to identify the chemical nature of these particles and quantify them. Furthermore, the quantification of synthetic or organic fibres was also carried out. The results show that XPS microplastics (MP-XPS) contaminate food products at a level ranging from 4.0 to 18.7 MP-XPS/kg of packaged meat. Analysis shows that these microplastics are likely to come from the XPS trays. These particles are difficult to remove by mere rinsing and are probably cooked before being consumed. However, at this stage, it is not clear from the scientific literature whether there is a potential risk to humans associated with the ingestion of MP-XPS. In addition to these MP-XPS, it should also be pointed out that fibres can also contaminate meat.

**Keywords**

Microplastics, extruded polystyrene, fibres, packaging, contaminant, human alimentation

<footnote><sup>a</sup> IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France</footnote>

<footnote><sup>b</sup> IRDL UMR CNRS 6027, Université Bretagne Sud, 56000 Vannes, France</footnote>

<footnote><sup>c</sup> Archipel institute, Université Bretagne Sud, 56100 Lorient, France</footnote>
# 1. Introduction

Between 1950 and 2015, 7,800 million tons of plastic were produced, half of which between 2002 and 2015 (Geyer et al., 2017). The physical properties of plastic materials make them essential in industrialized societies. In Europe, the packaging, construction, and automotive sectors account for nearly 70% of the demand for plastic, with nearly 40% for packaging alone (PlasticsEurope, 2018). In the food sector, the use of plastic packaging helps in the storage, transport, protection, and preservation of products while reducing their waste (Lange and Wyser, 2003; Mathlouthi, 2013; Piringer and Baner, 2008; PlasticsEurope, 2012). Because some plastics such as expanded polystyrene (EPS) or extruded polystyrene (XPS) provide a good protection barrier from oxygen, water vapour, and microorganisms, they facilitate the preservation of food products at a desired temperature; hence, they are widely used in food packaging. However, it has been recently reported that packaging may release plastic particles and subsequently contaminate our food with plastic fragments (Oßmann et al., 2018; Schymanski et al., 2018; Winkler et al., 2019).

The presence of small plastic particles in the natural environment has been known since the early 1970s (Buchanan, 1971), but it is only in the early 2010s that their presence in food was reported (Barboza et al., 2018). Among these, microplastics, namely plastic particles smaller than 5 mm in size (GESAMP, 2019), were found. In 2013, a study carried out on honey and sugar coming from different countries revealed contamination by fibres and fragments (Liebezeit and Liebezeit, 2013). Although no chemical analysis was performed to assess the chemical nature of these particles, a connection was established between the morphology of these fragments and the plastic bags used by beekeepers to supply sugar to bees. In 2014, the identification of microplastics in mussels (*Mytilus edulis*) grown for human consumption suggests that humans ingest these particles (Van Cauwenberghe & Janssen, 2014). To date, several studies have reported the presence of plastic particles in seafood and fish for human
consumption (Azevedo-Santos et al., 2019; Barboza & Gimenez, 2015). Microplastics have also been observed in salt (Gündoğdu, 2018; Iñiguez et al., 2017; Karami et al., 2017; Yang et al., 2015), in beers (Kosuth et al., 2018; Liebezeit and Liebezeit, 2014), and in water bottles (Mason et al., 2018). These microplastics, generally smaller than 100µm, probably come partly from the packaging and/or bottling process (Mason et al., 2018). A large-scale study of tap water showed that 81% of the water sampled was contaminated mainly by fibres of which an unknown part is of synthetic origin (Kosuth et al., 2018). Fibres can be defined as particles of equal thickness along their entire length, the difference between artificial and natural fibres being based on the presence or absence of visible cellular or organic structures (Hidalgo-Ruz et al., 2012). For the purposes of this publication, no distinction will be made between artificial and natural fibres. The origin of the fibres observed in food is not always clear, but airborne contamination is often thought of. The atmosphere is an important vector of microplastics, as shown by the atmospheric deposition of synthetic fibres in Paris (Boucher and Friot, 2017; Dris et al., 2016). These fibres are also omnipresent in our indoor environment to the point of posing a significant risk of contamination of samples (Dehaut et al., 2019). It is commonly accepted that synthetic textiles are the main source of these fibres (Boucher and Friot, 2017; Prata, 2018).

This study is part of the OceanWise project, a European project supported by the European funding program INTERREG Atlantic Area. OceanWise aims to jointly develop a set of long-term measures to reduce the impact of expanded and extruded polystyrene (EPS/XPS) products in the North-East Atlantic Ocean. Some economic activities, which generate EPS/XPS waste, are particularly investigated in the OceanWise project: the fishing industry (fisheries, aquaculture, sea-food), the food industry (supermarket chains, distribution of vegetables, fish, meat, fruit), consumer goods, outdoor festivals, and tourism. In this context, several observations of more or less free sub-millimetre particles inside food packaging with an XPS bottom containing meat were made during a preliminary study for the OceanWise project tests.
These microparticles have the same colour as the XPS food packaging that contained them.

Faced with these elements, it was therefore decided to verify the following hypotheses: Are these particles microplastics of extruded polystyrene (MP-XPS)? What is the estimated mass of MP-XPS per mass of meat? How many fibres are present on the surface and inside the food packaging? In an attempt to determine the origin of the particles and fibres as well as the timing of the deposition, the distribution of MP-XPS was studied inside and outside the tray. Thus, this preliminary study, limited to the case of France, seeks to answer these questions and identify some elements of discussion regarding the possible origins of these particles, as well as the possible consequences of ingesting them for human health.

## 2. Materials and methods

### 2.1. Sample collection and preparation

This study focuses on meat products (chicken) packed in extruded polystyrene trays (230x140x20mm). The mass of the pieces of meat was determined by reading the mass displayed on the label on the plastic packaging. Samples of meat from brands B, C, D had a roughly equivalent mass (on average close to 250g), while brand A meat samples were slightly larger in mass (about 315g) (Table 5). Products from four different brands (named A, B, C, and D) were purchased in a local supermarket (n=3 by brand). No special conditions were taken to transport (in few minutes) them to the laboratory.
<table><caption>Table 5. Sample characteristics.</caption><thead><tr><td>Brand</td><td>Colour of the tray</td><td>Meat</td><td>Mass of meat (g)</td></tr></thead><tbody><tr><td>A</td><td>Black</td><td>White chicken breast</td><td>315±15</td></tr><tr><td>B</td><td>Yellow</td><td>Turkey escalope</td><td>239±47</td></tr><tr><td>C</td><td>Yellow</td><td>Turkey escalope</td><td>254±36</td></tr><tr><td>D</td><td>Yellow</td><td>Turkey escalope</td><td>240±47</td></tr></tbody></table>

It is necessary to take into consideration all the surfaces of the packaging in order to describe the state of contamination of the tray and obtain information on the sources of this contamination. Thus, the outside of the packaging (i.e. tray and plastic film) was first rinsed with distilled water. This rinsing water was then analysed to determine the amounts of particles and fibres on the outside of the packaging. In order to avoid generating MP-XPS when tearing off the plastic film sealing the trays, the tray openings were made with a scalpel. Then, after opening, the meat was rinsed thoroughly until the thin layer of fat covering the surface of the samples was completely collected. Finally, the inside of the tray and plastic film were rinsed with distilled water. The rinsing water was then vacuum filtered (Buchner JIPO, 62 mm) on a glass microfiber filter (pore diameter: 0.8µm, diameter 55 mm, Fisherbrand MF300). This step allows the fat layer to be vacuumed with the water, while the particles remain trapped on the surface of the filter. In order to limit external contamination by fibres, rinsing the packaging and meat and filtering were carried out under a funnel hood. The operators conducting the experiments wore a cotton grown and nitrile gloves to avoid contamination by fibres from their clothing. The glassware used was systematically rinsed at least three times with distilled water and one last time with ethanol. After the filtration step, the filters were stored in glass petri dishes also in order to limit contamination by the fibres present in the ambient environment.
## 2.2. Isolation, visual characterization, and identification of microplastics

A dissection microscope (30X magnification) was used to count fibres and potential MP-XPS. All fibres were counted, but their chemical nature was not identified. The spectra of all recovered fragments were acquired using an Attenuated Total Reflection Fourier Transform Infrared microspectrometer (ATR-FTIR Lumos, Bruker). All spectra were recorded in the absorbance mode in the 4,000-600 cm⁻¹ region with 4 cm⁻¹ resolution and 16 scans. The spectra were acquired and compared to reference spectra of polystyrene.

The maximum and minimum Feret diameters of the particles were measured using the camera of the Lumos microscope associated with the OPUS software. These diameters were then used to estimate the volume of the particles. For this calculation, the shape of the particle was approximated to a spheroid, with the two smallest axes considered as equal.

## 2.3. Estimated per capita consumption of microplastics and statistical analysis

Since the microplastics were too light to be weighted by a precision balance (readability: 0.1mg), the mass of the particles was calculated according to two density hypotheses. The low hypothesis corresponds to the density of extruded polystyrene (40 kg.m⁻³), whereas the high hypothesis corresponds to that of polystyrene (1040 kg.m⁻³) (M. Kedzierski et al., 2017). The per capita consumption of MP-XPS was calculated using the weight of the meat samples and the average meat consumption rate of a French person (Tavoularis and Sauvage, 2018). The following equation was used:

$$N_t = N_{MP}/m*m_t \quad (Equation 7)$$
PART 3. Microplastic contamination of packaged meat: occurrence and associated risks

Where, N<sub>t</sub> is the number of microplastics per person and per day, N<sub>MP</sub> is the number of microplastics per tray, m is the mass of meat in the tray, and m<sub>t</sub> is the mass of meat consumed per unit of time and per person (135 g/d/person).

The equality of group averages was then measured using the Excel Student and the Fisher tests.

**3. Results**

3.1. Particles

The characteristics of the microparticles were the same as those of the XPS tray: presence of vacuoles, identical colour, and identical chemical nature. There is therefore no doubt that they came from the tray. FTIR spectra and the microscopic observations of the collected particles showed the presence of MP-XPS microparticles inside the packaging as well as on its outer surface. It should also be noted that some MP-XPS were found between the meat and the plastic seal (Figure 25). The MP-XPS particles stuck on the surface of the meat were difficult to recover during the rinsing phase. A thorough rinsing was necessary each time to recover the particles, usually also by removing the layer of fat from the surface of the meat. The average size of MP-XPS, measured along the main axis, was comprised between 300 and 450 µm. On the secondary axis, the average size of MP-XPS varied between 130 and 250 µm. The variability in particle size was quite high within the packaging of the same brand. The colour of the MP-XPS was generally the same as that of the XPS tray. The morphology of the particles was variable. Some seemed to belong to porosity walls, others were more or less compressed blocks of XPS. Thus, we used the density of XPS (40 kg/m³) and polystyrene (1,040 kg/m³) to calculate the total mass of MP-XPS per sample (M Kedzierski et al., 2017).
<figure><img src="image_28.png" /><figcaption>Figure 25. MP-XPS observed with a dissecting microscope (the Photoshop software was used to improve the image brightness).</figcaption></figure>

The observed particle was trapped between the sealing film and the meat. In this example, the particle was black because the tray itself was that colour. In the yellow trays, the particles were yellow. In this example, the particle contrasts with the colour of the meat, making it very easy to observed. The structure of the particle corresponds, for the thinnest parts, to the walls of the porosity of the XPS, and for the thickest part, to a fragment of XPS. Therefore, the density of these MP-XPS varies extensively, as noted above.

The average quantities of MP-XPS observed on the external surface of the food packaging varied, depending on the brands, between 1.1±1.9 and 10.8±6.0 MP-XPS/kg of packaged meat (Figure 26). Variations were large for the packaging samples of the same brand. The amounts of MP-XPS recovered inside the packaging were on average higher than those found outside for brands A and B whereas the opposite was observed for brand C. The average quantities of MP-XPS observed on the internal surface of food packaging varied, depending on the brands, between 4.0±4.5 and 18.7±8.3 MP-XPS/kg of packaged meat. The amounts recovered inside and outside were similar for brand D. Due to the large variability between samples of the same brand, there was no statistically significant difference between the quantities of MP-XPS inside and outside the packaging. For all the brands under investigation, the number of MP-XPS was generally below 20. Although the amounts of MP-XPS found on the surface of packaging A
PART 3. Microplastic contamination of packaged meat: occurrence and associated risks

were on average lower than those of other brands, there was also no statistically significant
difference from one brand to another. Similarly, although the quantities of particles found inside
tray B were on average much higher than those observed in the other trays, no statistical
differences were clearly identified. However, the p-values were very close to 0.05. There is
therefore a weak statistical presumption that brand B meat is more contaminated than other
brands.

<figure><img src="image_29.png" /><figcaption>Figure 26. Number of MP-XPS per kilogram of meat observed at the surface of and inside the food packaging for the different brands.</figcaption></figure>

The masses of MP-XPS were calculated per meat mass according to the two extreme particle
densities (40 and 1,040 kg/m³) (Table 6). In the first case, the masses of MP-XPS present on
the outer surface of the packaging ranged from 5 µg/kg of packaged meat (brand A) to 93 µg/kg
(brand B). Within the packaging, the masses of MP-XPS varied between 2 µg/kg (brand D) and
402 µg/kg (brand B). In the second case, the masses of MP-XPS present on the outer surface of
the packages varied between 0.14 mg/kg of packaged meat (brand A) and 2.4 mg/kg (brand B).
Inside the packaging, the masses of MP-XPS varied between 54 µg/kg (brand D) and
10.5 mg/kg (brand B).
<table><caption>Table 6. Mass of MP-XPS per kilogram of meat for the different brands estimated from each density hypothesis.</caption><thead><tr><th>Brand</th><th></th><th>Hypothesis 1: 40 kg/m3<br>mass of MP-XPS in mg/kg</th><th>Hypothesis 2: 1,040 kg/m3<br>mass of MP-XPS in mg/kg</th></tr></thead><tbody><tr><td rowspan="2">A</td><td>Outside</td><td>0.005 ± 0.009</td><td>0.14 ± 0.24</td></tr><tr><td>Inside</td><td>0.09 ± 0.12</td><td>2.2 ± 3.1</td></tr><tr><td rowspan="2">B</td><td>Outside</td><td>0.09 ± 0.16</td><td>2.4 ± 4.2</td></tr><tr><td>Inside</td><td>0.4 ± 0.5</td><td>10.5 ± 13.7</td></tr><tr><td rowspan="2">C</td><td>Outside</td><td>0.02 ± 0.03</td><td>0.5 ± 0.8</td></tr><tr><td>Inside</td><td>0.2 ± 0.2</td><td>4.5 ± 4.5</td></tr><tr><td rowspan="2">D</td><td>Outside</td><td>0.05 ± 0.08</td><td>1.2 ± 2.0</td></tr><tr><td>Inside</td><td>0.002 ± 0.001</td><td>0.05 ± 0.03</td></tr></tbody></table>

Based on the average French daily consumption of meat, the mass of XPS observed inside the packaging and potentially ingested per day and per year was calculated (Table 7). If the particle density was 40 kg/m³ (low hypothesis), the average mass of XPS ingested per day could range from 0.1 µg/d (brand D) to 54 µg/d (brand B). Per year, this would vary between 0.04 mg/y (brand D) and 19.7 mg/y (brand B). For a particle density of 1,040 kg/m³ (high hypothesis), the average mass of XPS ingested per day could vary between 7 µg/d (brand D) and 1.4 mg/d (brand B). Per year, this could range from 2.6 mg/y (brand D) to 511 mg/y (brand B).
<table><caption>Table 7. Consumption of MP-XPS per person based on a meat consumption of 135 g/d/person.</caption><thead><tr><th>Brand</th><th>MP-XPS density</th><th>Daily consumption<br>(mg/d)</th><th>Annual consumption<br>(mg/y)</th></tr></thead><tbody><tr><td rowspan="2">A</td><td>Hypothesis 1: 40 kg/m3</td><td>0.01 ± 0.02</td><td>4.2 ± 6.0</td></tr><tr><td>Hypothesis 2: 1,040 kg/m3</td><td>0.3 ± 0.4</td><td>110.1 ± 154.9</td></tr><tr><td rowspan="2">B</td><td>Hypothesis 1: 40 kg/m3</td><td>0.5 ± 0.07</td><td>19.8 ± 26.0</td></tr><tr><td>Hypothesis 2: 1,040 kg/m3</td><td>1.4 ± 1.9</td><td>515.2 ± 675.3</td></tr><tr><td rowspan="2">C</td><td>Hypothesis 1: 40 kg/m3</td><td>0.02 ± 0.02</td><td>8.6 ± 8.4</td></tr><tr><td>Hypothesis 2: 1,040 kg/m3</td><td>0.6 ± 0.6</td><td>223.2 ± 219.4</td></tr><tr><td rowspan="2">D</td><td>Hypothesis 1: 40 kg/m3</td><td>0.0003 ± 0.0001</td><td>0.1 ± 0.05</td></tr><tr><td>Hypothesis 2: 1,040 kg/m3</td><td>0.007 ± 0.003</td><td>2.7 ± 1.3</td></tr></tbody></table>

## 3.2. Fibres

On average, the number of fibres observed on the surface of the food packaging was between 134 fibres/kg (brand C) and 221 fibres/kg (brand B) (Figure 27). For most of the brands tested, the number of fibres inside the packaging was between 18 fibres/kg (brand D) and 164 fibres/kg (brand B). For brands A, C, and D, the quantities of fibres were therefore higher outside than inside. In the case of brand D, the amounts of fibres were about 11 times lower on the inside of the package than on the outside. For brands A and C, the amounts were between 2 and 5 times lower. However, this was not true for brand B, where the number of fibres inside and outside of the packaging was quite similar. Thus, the differences between the amounts observed inside and outside the packaging were significant for brands A, C, and D. For fibres on the external
PART 3. Microplastic contamination of packaged meat: occurrence and associated risks

food packaging, there was no statistical difference between the brands, nor was there any
statistical difference between brands for the fibres present inside the packaging. This was due
in particular to the variability observed from one sample to another for the same brand.

<figure><img src="image_30.png" /><figcaption>Figure 27. Amounts of microfibres per kilogram of packaged meat observed on the surface and inside of the food packaging examined. * Results that show statistical differences (p-value < 0.05).</figcaption></figure>

4. Discussion

4.1. Contamination of the surface of meat products with microplastics

4.1.1. Sources of MP-XPS

To our knowledge, this study is the first one to draw attention to the microplastics found on the
surface of meat products sealed in their packaging. This contamination necessarily raises the
question of the origin of the microplastics. The observation of the presence of MP-XPS inside
and outside the tray, as well as between the tray and the meat, and between the meat and the
protective film, leads to the hypothesis that the deposition of particles starts before the meat
was deposited and lasts at least until the film was closed. It is possible that the packaging may
be contaminated by XPS dust suspended in the air of the production buildings. The MP-XPS are easily airborne because of their low size and mass and because their electrostatic properties make them sticky. It should also be noted that the presence of microplastics trapped between the meat and the plastic film that seals the tray implies that MP-XPS are present, suspended in the air, in the food preparation areas.

### 4.1.2. *Areas for study improvement*

Feedback on the protocol proposed within the framework of this study has generated several propositions for improvement. In particular, it would be desirable to work on more samples of the same brand. When the protocol was designed, working on the basis of a triplicate seemed relevant. However, due to the variability observed from one sample to another, it appears a *posteriori* that this number could be increased. In the case of the study of microplastics ingested by living organisms, a minimal number of 50 individuals per species is recommended to obtain a representative sample (Dehaut et al., 2019). This recommendation may also be relevant to the study of microplastic contamination of packaged food.

## 4.2. *Ingesting MP-XPS: A threat to human health?*

Regardless of the source of these MP-XPS, it should be noted that despite the thorough rinsing of the surface of the meat examined, plastic particles often remained trapped on the meat surface. Thus, whether the meat is rinsed or not, the MP-XPS are likely to be present when the food is cooked, and some will be ingested.

### 4.2.1. *Potential impacts of polystyrene microplastics (MP-PS) on human health*

While it has sometimes been argued that certain species fished are potential microplastic vectors for humans, extraction from the digestive system (containing microplastics) before consumption greatly reduces this risk (Alomar and Deudero, 2017; Rummel et al., 2016; Sanchez et al., 2014; Van Cauwenberghe et al., 2015; Van Cauwenberghe and Janssen, 2014;
Vroom et al., 2016). Another source of contamination of human food comes from the packaging (Schymanski et al., 2018). The masses of MP-XPS ingested per day and per person could reach 1.4 mg based on the results obtained in this study, but there is no reference or standard for determining whether or not this value is dangerous to human health. In fact, the potential impact of MP-PS ingestion on human health remains very limited (Wang et al., 2019). A study conducted on human epithelial (HeLa) and cerebral (T98G) cell lines has shown that PS microspheres (diameter 10µm) caused oxidative stress (Schirinzi et al., 2017). On the contrary, MP-PS (1, 4 and 10µm) do not seem to have an impact on some human immune cells (macrophages) (Stock et al., 2019). In mice exposed to 0.5-50 µm polystyrene particles, disruptions in energy and lipid metabolism, oxidative stress, neurotoxic disorders, and microbiotic dysbiosis were observed that suggest potential risks to mammalian health (Deng et al., 2017; Lu et al., 2018). However, these results are qualified by a recent study suggesting that, under certain conditions, oral exposure to microplastic particles does not pose an acute risk to mammalian health (Stock et al., 2019).

However, several limitations to the transferability of these hazardous effects to the human case must be mentioned. First, the sensitivity to plastics may vary between animal species (Walum, 1998). Second, it is necessary that the plastic quantities ingested and the exposure duration of the animals be relevant to the quantities actually observed in their natural environment or, as in this case, in human food (Bour et al., 2018; Lönnstedt and Eklöv, 2016). In experiments conducted on mouse exposure to MP-PS, the dose tested was 0.1 mg/d, which is in line with the amounts that could be ingested by humans (Deng et al., 2017). However, this dose is much higher if we consider the difference in body weight between a mouse and a human being. Thus, it is important to note that the polystyrene particles used in these studies are one to two orders of magnitude smaller than those observed in the present study. Nevertheless, it cannot be completely excluded that polystyrene particles from a few micrometres to a few tens of
micrometres in size were not effectively detected and extracted from the surface of the samples.

However, while it is possible that the total number of microplastics may be underestimated, the very low mass of these fine particles should not have too much influence on the total mass values of MP-XPS calculated in this study. However, it should be noted, that it is essentially on this size range of small microplastics (less than a few tens of microns) that the discussion on the toxicity of polystyrene particles is based. Therefore, a better assessment of the amount of these small microplastics present on the surface of foods appears to be important to better identify the associated risks. Finally, the number of studies on the impact of MP-PS on mammals is very low, which makes it difficult to accurately assess their potential impact on humans (Rainieri and Barranco, 2019).

4.2.2. *Styrene desorption*

In addition, for polystyrene, there is a risk of desorption of styrene monomers during the use
phase (Rist et al., 2018). Styrene is quickly absorbed by organisms through ingestion or
inhalation (Bonnard et al., 2016). It is stored in fatty tissues where it is rapidly metabolized
(half-life of about 6 hours). After metabolisation, it is mainly eliminated by urine. Styrene
therefore does not accumulate in organisms. In terms of chronic toxicity, in rats, ingestion of
high doses of styrene (1.0 g/kg/d, 5d/week, 28d) causes irritation of the gastrointestinal tract,
which is lethal. This dose corresponds, for a person weighing 70kg, to about 50,000 times the
maximum daily mass of MP-XPS potentially ingested per day and per person recorded in our
study (1.4 mg/d). Since a small fraction of styrene is desorbed from MP-XPS, the doses are
actually even lower.

At lower doses, ingestion induces changes in kidney and liver weight. Styrene is metabolized
by cytochrome P450 enzymes to styrene-7,8-oxide that undergoes hydration or conjugation
with glutathione (Shen, Li, Ding, & Zheng, 2014). In mice, styrene is involved in lung tumour
development, whereas no data indicate a similar effect in humans (Cruzan et al., 2018). The
derived no-effect level (DNEL) of styrene is 7.7 µg/kg bw/d (European Chemicals Agency, 2019e), which represents, in the framework of our study, about 0.4 times the maximum daily mass of MP-XPS potentially ingested per day and per person weighing 70 kg. However, again, the amounts of styrene released from MP-XPS are most likely much lower. Finally, in humans, styrene absorption results in memory loss, difficulties in concentration and learning, brain and liver damage, and cancer (Gibbs and Mulligan, 1997).

More generally, according to a recent study, the toxicity of polystyrene packaging can vary greatly from one polystyrene sample to another (Zimmermann et al., 2019). Thus, some PS samples were cytotoxic to the cells used in the AREc32 test at lower concentrations than the other plastics tested. This study also highlights a toxicity linked to oestrogenic (Yeast Estrogen Screen) and especially anti-androgenic (Yeast Anti-Androgen Screen) effects for some samples. This implies that some additives used in the food packaging have endocrine activity.

Due to higher average meat consumption among men than women (Hercberg & Tallec, 2000), there is a differential exposure to MP-XPS between the sexes. Similarly, in France, the protein intake reaches its maximum around adolescence (Hercberg & Tallec, 2000), corresponding with a period of vulnerability to endocrine disruptors.

Thus, the ingestion of microplastics could be an additional route of contamination that would add to the more traditional route of contamination via food. However, this contamination would be several orders of magnitude lower than that passing through food products (Rist et al., 2018).

### 4.2.3. Cooking microplastics

Cooking conditions can vary considerably from one cooking method to another. Thus, the temperatures reached during cooking may vary between 100 and 230°C or much more for open fire grills. When subjected to temperatures between 200 and 300°C, the molecular weight of polystyrene decreases due to thermal degradation inducing random scission of the carbon chain,
and disproportionation of the macroradicals formed, leading to the release of many degradation products (McNeill et al., 1990). At 200°C, the rate of volatile fragments formed is low, but the amounts of degradation residues may be significantly higher. At around 300°C, gaseous styrene is mainly produced, but so are other compounds such as ethylbenzene, methylbenzene (or toluene), benzene, phenylpropene, α-methylstyrene, 1-methylindene, and naphthalene (McNeill et al., 1990). The toxicity of these molecules cannot be established for the doses of MP-XPS quantified on the surface of the meat even if an endocrine activity of these molecules cannot be completely excluded (Zimmermann et al., 2019). Furthermore, based on the DNEL of styrene (7.7 µg/kg bw/d), low toxicity leading to irritation cannot be completely ruled out (European Chemicals Agency, 2019).

### 4.3. Microfibres: another contaminant

The number of fibres observed inside the trays is of the same order of magnitude as that observed in previous studies on other food products; as for honey, sugar, or salt, the observed quantities were generally lower than 1,000 fibres per kg of food (Gündoğdu, 2018; Iñiguez et al., 2017; Karami et al., 2017; Liebezeit and Liebezeit, 2013). If, in the case of these studies, the origin of the contamination is not always easy to determine (contamination in the natural environment or during the manufacturing process of the product), in the case of our study, the presence of fibres inside the tray implies the presence of these fibres in the production environment of the food product. In the absence of analysis of procedural blank, it cannot be totally excluded that a fraction of the fibres observed are derived from airborne contamination. However, the differences observed, in particular between the inner and outer surfaces of the trays, are statistically significant. It is highly unlikely that, under similar study conditions such large variations can be due to contamination without affecting the variance within the same brand.
The chemical nature of these fibres, outside the scope of the preliminary analysis, was not analysed. Thus, it is not possible to specify whether these fibres are mineral or organic. The impact of the inhalation of man-made mineral fibres is well known; as a function of different parameters such as particle size and composition, they have the intrinsic potential to induce oxidative stress, inflammation, genotoxicity, and carcinogenicity (Greim, 2004).

Similarly, the consequences of the inhalation of man-made organic fibres is known (Gasperi et al., 2018; Greim, 2004). For example, various studies conducted on cohorts of textile workers have shown no or a moderate impact on the respiratory tract (Warheit et al., 2001). The impact of fibre ingestion is less well documented as this mode of contamination appears, in the air, to be secondary to respiration. Very few studies report cases of airborne ingestion of these fibres by living beings (Cook and Olson, 1979; Zhao et al., 2016). Hence, apart from the particular case of certain mineral fibres (e.g. asbestos), which has been well documented for several decades (Davis, 1981), the impact of fibre ingestion on human health is poorly described in the scientific literature. Nevertheless, it should also be noted that the average amount of fibres outside the tray is up to 10 times higher than inside the tray. It thus appears that the packaging plays a protective role against microfibres.

5. **Conclusion**

Only few scientific studies report the presence of microplastics that contaminate food. Our study, by assessing the presence of microplastics on the surface of meat products, extends the state of knowledge on the contamination of human food by microplastics. These microplastics are highly adherent to the meat surface and are likely to be eaten by consumers. Although polystyrene trays are made of polystyrene suitable for food contact, the presence of MP-XPS on the food surface is potentially problematic due to the toxicity of the microparticles, the potential desorption of styrene, and the formation of degradation products during cooking. Nevertheless, given current knowledge on the issue, it should be noted that the comparison of
PART 3. Microplastic contamination of packaged meat: occurrence and associated risks

the amounts of MP-XPS observed in the trays with the data available in the scientific literature
does not enable us to definitively conclude on the existence or not of potential risks for humans.

As a consequence, this preliminary investigation should be expanded and further developed
along several lines of investigation. First, it would be relevant to identify the sources of
contamination in association with possible distinct packaging processes. This step is necessary
to propose counter measures that could reduce exposition to MP-XPS. Second, the risks
associated with the regular ingestion of MP-XPS should be clarified. In addition, greater
knowledge of the molecules that can be desorbed by MP-XPS is necessary, especially if they
behave as endocrine disruptors.
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PART 3. Microplastic contamination of packaged meat: occurrence and associated risks

Zhao, S., Zhu, L., & Li, D. (2016). Microscopic anthropogenic litter in terrestrial birds from Shanghai, China: Not only plastics but also natural fibers. *Science of the Total Environment*, 550, 1110–1115. https://doi.org/10.1016/j.scitotenv.2016.01.112

Zimmermann, L., Dierkes, G., Ternes, T. A., Völker, C., & Wagner, M. (2019). Benchmarking the in Vitro Toxicity and Chemical Composition of Plastic Consumer Products. *Environmental Science & Technology*, 53(19), 11467–11477. https://doi.org/10.1021/acs.est.9b02293
WAYS TO REDUCE POLYSTYRENE WASTES
PART 4. Production of foamed PLA

Benjamin Gallard<sup>b</sup>, Mikaël Kedzierski<sup>a</sup>, Anne Bergeret<sup>b</sup>, Gwénaël Le Maguer<sup>c</sup>, Stéphane Bruzaud<sup>a</sup>

<sup>a</sup> IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France

<sup>b</sup> C2MA, Ecole des Mines d'Alès, Alès, France

<sup>c</sup> Archipel institute, Université Bretagne Sud, 56100 Lorient, France

# 1. Introduction

Within the OceanWise project, different options need to be addressed in order to reduce the pollution of the marine environment by EPS-based plastic waste. Among the solutions being considered is the replacement of EPS and XPS with materials that have a lower environmental impact. In this context, IRDL was particularly interested in the case of foamed polylactic acid (PLA), previously identified in the OceanWise workpackages as a possible solution. In fact, PLA is a 100% biosourced polymer obtained by converting lactic acid nowadays produced from the fermentation of food sugars from the production of corn, beet, tapioca or sugar cane (Penu and Helou, 2017). PLA has mechanical properties similar to those of traditional polymers and can be processed without significant changes to traditional polymer manufacturing processes (Graupner et al., 2009; Lim et al., 2008; Matuana, 2008). PLA are nowadays mainly used for food applications, for example as food packaging such as foamed thermoformed trays (Penu and Helou, 2017). These packages are found partly in supermarkets and partly in fast-food restaurants, mainly for foods with a short shelf life (Penu and Helou, 2017). Indeed, the low water barrier of PLA limits its use as long-life packaging. PLA can be used as an intermediate layer in multilayer products or in a blend with other polymers (Penu and Helou, 2017). This polymer is also biodegradable under certain conditions, particularly in industrial compost (EN 13432).
Among the different ways of foaming a plastic, chemical foaming is commonly used. This technique consists of dispersing a chemical foaming agent (CFA) in the polymer matrix (Julien et al., 2012). During the process, the increase in temperature leads to the release of a gas by the CFA which reduces the density of the material from 50% to more than 95% (Hansen, 1993).

However, in the case of PLA, the process temperature is relatively low (Lim et al., 2008) and implies that the foaming operation is more complex than for traditional polymers. If a first study has shown that this operation can be carried out (Julien et al., 2012), some aspects of the protocol need to be improved and tested as part of the OceanWise project.

In this context, the IRDL commissioned C2MA to carry out these tests. The *Centre des Matériaux des Mines d'Alès* (C2MA) develops and studies innovative materials in the field of polymer materials and mineral or mineral matrix materials for civil engineering. This laboratory has been working since 2012 on the foaming of PLA and therefore has a good expertise and the material capacities to provide the foamed PLA necessary for the IRDL experiments. In this context, this work will seek to find the optimal conditions for the foaming of a PLA. Once these conditions have been found, C2MA will provide 10m of foamed PLA plates.

## 2. Materials and methods

### 2.1. *Materials*

#### 2.1.1. *Preparation of the raw materials*

Raw materials were dried in PIOVAN desiccators at 80°C for 1 night to avoid degradation by hydrolysis during the extrusion process.

The raw materials were:

- PLA: PLE 003 from NaturPlast

- Expanding agent: Hydrocerol CT3108 from Clariant

- Chain extender: CESA-EXTEND BLA0050109-ZN
Several compositions were made by varying the percentages of additives (Table 8).

<table><caption>Table 8. Formulations carried out.</caption><thead><tr><th>Formulation</th><th>Matrix</th><th>% CT3108</th><th>CESA-<br>EXTEND</th><th>Operating<br>conditions</th></tr></thead><tbody><tr><td>1</td><td>PLE 003</td><td>2</td><td>0</td><td>C1</td></tr><tr><td>2</td><td>PLE 003</td><td>8</td><td>0</td><td>C1</td></tr><tr><td>3</td><td>PLE 003</td><td>4</td><td>0</td><td>C2</td></tr><tr><td>4</td><td>PLE 003</td><td>2</td><td>5</td><td>C2</td></tr><tr><td>5</td><td>PLE 003</td><td>2</td><td>5</td><td>C3</td></tr></tbody></table>

### 2.1.2. Extrusion

Shaping of the compositions was carried out using a ThermoFisher Scientific single-screw extruder and a flat die with a width of 100 mm and a thickness of 0.9 mm. The L/D (Length/Diameter) ratio of the extruder is 25. The extrusion screw is a Maddoc type screw with a diameter of 19 mm. A transport bench was used to cool the polymer in ambient air and to avoid deformation of the plate.

The polymer and additives were mixed manually and fed into the feed hopper of the single screw. The process conditions were developed according to previously developed works (Julien et al., 2012). Different conditions were tested in order to obtain an optimal vacuum fraction rate (Table 9).
<table><caption>Table 9. Condition of PLA extrusion tested.</caption><thead><tr><th>Conditions</th><th>Rotational velocity (r/min)</th><th>Area 1 T (°C)</th><th>Area 2 T (°C)</th><th>Area 3 T (°C)</th><th>Die T (°C)</th><th>Torque power (N.m)</th><th>Pressure (Bar)</th></tr></thead><tbody><tr><td>C</td><td>100</td><td>150</td><td>160</td><td>175</td><td>175</td><td>NA</td><td>NA</td></tr><tr><td>C2</td><td>100</td><td>150</td><td>160</td><td>175</td><td>185</td><td>50</td><td>3</td></tr><tr><td>C3</td><td>100</td><td>150</td><td>160</td><td>175</td><td>185</td><td>50</td><td>0.9</td></tr></tbody></table>

## 2.2. Characterization

The density measurements were carried out following a previous protocol (Julien et al., 2012). A caliper (accuracy 0.01mm) was used to measure the lengths, widths and thicknesses of the films. Two balances were used to determine the weight (accuracy 0.001g and 0.01g). The calculation of the void volume fraction (vf) is carried out according to the equation below (eq. 13) and with reference to the density value of the PLA PLE 003 data sheet of 1250 kg/m³.

$$Vf = \left(1 - \frac{\rho f}{\rho p}\right) * 100 \quad (Equation 8)$$

With, $\rho p$ the apparent density of extruded solid PLA and $\rho f$ the apparent density of extruded cellular PLA.

# 3. Results

## 3.1. Void fraction

The results obtained show variations in terms of void fraction depending on the formulation of the mixtures (Table 10). Thus, in the case of the first three formulations, the void fraction varied between 32 and 36% on average. This increase was anti-correlated with the increase in the
concentration of foaming agent, so it does not seem necessary to increase the concentration of foaming agent beyond 2%. However, even with this concentration, the void fraction rate remained relatively low, in the order of 36%. The physical properties of PLA could be improved by using the chain expander. Indeed, for both formulations 4 and 5, the void fraction rate reached values close to 47 to 49%. If these two samples had the same chemical composition, the different processing pressures explain the observed differences in the void fraction rate. Thus, sample 4 implemented under a pressure of 3 bars has a slightly higher expansion rate. The variability of the results for this process was also smaller.

<table><caption>Table 10. Void fractions as a function of the different formulations.</caption><thead><tr><th>Formulation</th><th>Width<br>(mm)</th><th>Length<br>(mm)</th><th>Thickness<br>(mm)</th><th>Weight<br>(g)</th><th>Density<br>(kg/m3)</th><th>Vf<br>(%)</th></tr></thead><tbody><tr><td>1</td><td>71.3±0.8</td><td>101.4±0.1</td><td>0.8±0.1</td><td>4.7±0</td><td>797.8±0</td><td>36.2±0</td></tr><tr><td>2</td><td>102.4±0.7</td><td>72.2±1.3</td><td>0.8±0.1</td><td>5.1±0</td><td>842.7±0</td><td>32.6±0</td></tr><tr><td>3</td><td>103.2±0.6</td><td>74.0±1.0</td><td>0.8±0</td><td>5.2±0</td><td>817.5±0</td><td>34.6±0</td></tr><tr><td>4</td><td>50.8±4.6</td><td>71.7±5.5</td><td>0.9±0</td><td>2.1±0.3</td><td>643.6±19.5</td><td>48.5±1.6</td></tr><tr><td>5</td><td>51.0±0.4</td><td>72.5±9.2</td><td>0.9±0</td><td>2.2±0.3</td><td>662.0±36.6</td><td>47.0±2.9</td></tr></tbody></table>

## 3.2. Sample observation

Observation in scanning electron microscopy of the samples created according to protocol 4, allowed to observe the characteristics of the porosity obtained (Figure 28). These appeared very different from the porosity of extruded polystyrene. Indeed, the interalveolar walls of the foamed PLA were very thick, often of the order of a hundred microns whereas they were generally less than one micron for an XPS. This is partly explained by the low pore density, which was quite widely dispersed in the matrix. They were also large (>300µm) and relatively
PART 4. Production of foamed PLA

homogeneous in terms of size compared to an XPS. However, this large pore size was not
sufficient to achieve a wall thickness similar to what can be observed in an XPS. This resulted
in very low pore connectivity. On the contrary, the pore connectivity with the sample surface
was high. Finally, the shape of the pores deviated strongly from a sphere. Indeed, a strong
flattening of the pores, leading to a significant elongation in the direction of extrusion, was
observed.

<figure><img src="image_31.png" /><figcaption>*Figure 28. SEM images of the PLA plate section.*</figcaption></figure>
4. **Conclusion**

The results show that the addition of a chain extender significantly increases the void fraction.

In addition, the increase in extrusion speed also contributes to increasing the void fraction.

Nevertheless, compared to extruded polystyrene, PLA expands very slightly. To significantly increase this expansion, the supercritical CO2 expansion technique should be used. However, this technique is very expensive and was not available at the time of manufacturing foamed PLA.

In the end, the protocol n°4 showed the best results (highest void fraction, low variability. It was therefore chosen to produce 30m of "expanded" PLA. This was cut into several samples of 500 * 100* 0.9mm. The void fraction of this production is on average 48.5% with a standard deviation of 1.6%.
References

Graupner, N., Herrmann, A. S., & Müssig, J. (2009). Natural and man-made cellulose fibre-reinforced poly(lactic acid) (PLA) composites: An overview about mechanical characteristics and application areas. *Composites Part A: Applied Science and Manufacturing, 40*(6), 810–821. https://doi.org/10.1016/j.compositesa.2009.04.003

Hansen, R. (1993). Handbook of polymeric foams and foam technology, Daniel Klempner and Kurt C. Frisch, eds., Hanser Publishers, Munich, Germany, 1992, 442 pp. price: $148.00. (Distributed in the U.S. and Canada by Oxford University Press, New York.). Journal of Polymer Science Part A: Polymer Chemistry, 31(5), 1344. https://doi.org/10.1002/pola.1993.080310535

Julien, J.-M., Bénézet, J.-C., Lafranche, E., Quantin, J.-C., Bergeret, A., Lacrampe, M.-F., & Krawczak, P. (2012). Development of poly(lactic acid) cellular materials: Physical and morphological characterizations. *Polymer*, 53(25), 5885–5895.
https://doi.org/10.1016/j.polymer.2012.10.005

Lim, L.-T., Auras, R., & Rubino, M. (2008). Processing technologies for poly(lactic acid). Progress in Polymer Science, 33(8), 820–852.
https://doi.org/10.1016/j.progpolymsci.2008.05.004

Matuana, L. M. (2008). Solid state microcellular foamed poly(lactic acid): Morphology and property characterization. *Bioresource Technology*, 99(9), 3643–3650.
https://doi.org/10.1016/j.biortech.2007.07.062

Penu, C., & Helou, M. (2017). Acide polylactique (PLA). ref. article: am3317. https://www.techniques-ingenieur.fr/base-documentaire/materiaux-th11/plastiques-et-environnement-42657210/acide-polylactique-pla-am3317/
# PART 5. Study of the properties of three objects made of expanded polystyrene and comparison with foamed PLA

Mikaël Kedzierski<sup>a*</sup>, Edgar Pigeon<sup>a</sup>, Gwénaël Le Maguer<sup>b</sup>, Stéphane Bruzaud<sup>a</sup>

## 1. Introduction

While it has been possible to produce a foamed biodegradable plastic, it is now important to look at some of these properties. Indeed, some of the chemical and mechanical characteristics of foamed PLA need to be targeted first and compared with those of PS to determine whether they are comparable. The aim of this section is therefore to show whether foamed polylactic acid (PLA) has the minimum characteristics to make it a potential replacement for foamed PS.

## 2. Materials and methods

### 2.1. *Samples*

Four materials were used in the OceanWise project: EPS plates used for thermal insulation, EPS boxes used in the fishing industry, XPS boxes used in food packaging and expanded PLA plates.

### 2.2. *Differential scanning calorimetry (DSC)*

Measurements in DSC allow the measurement of important thermal transitions of materials. These include the glass transition temperature (*Tg*), the crystallization temperature (*Tc*) and the melting temperature (*Tm*). The glass transition temperature can be described as the temperature range through which the material changes from a rubbery state to a glassy state as the temperature of the material decreases. This thermal transition is widely used to compare

<footnote><sup>a</sup> IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France</footnote>

<footnote><sup>b</sup> Archipel Institute, Université Bretagne Sud, 56100 Lorient, France</footnote>
polymeric materials and will determine whether or not foamed PLA can be used under the same thermal conditions as the various PS-based objects.

To determine this value, the samples were analysed using a Mettler Toledo DSC 3. In the case of the foamed polystyrene samples, a first heating cycle was performed by heating the sample from 25 to 150°C at a heating rate of 20°C/min. This first step was followed by a temperature stabilization step for 1 minute, before starting the last step of this cycle. This consisted of cooling the sample (decrease of 20°C/min) until the sample returned to the initial temperature (25°C). After holding at this temperature for 1 minute, a second cycle similar to the first was performed. In the case of the foamed PLA samples, a first heating cycle was performed by heating the sample from 25 to 125°C at a heating rate of 20°C/min. This first step was followed by a temperature stabilization step for 1 minute, before starting the last step of this cycle. This consisted of cooling the sample (decrease of 20°C/min) until the sample returned to the initial temperature (25°C). After holding at this temperature for 1 minute, a second cycle similar to the first was performed.

### 2.3. Energy dispersive X-ray spectroscopy

Plastic surface imaging was performed by using a Scanning Electron Microscope (SEM; JEOL 6460-LV) at 10 kV and 20 kV in secondary electrons image (SEI). The chemical analysis was realized using backscattered electron image (BSE) coupled with Energy Dispersive X-ray spectroscopy (EDS; Oxford Instrument X-ACT SATW 10mm2) at 10 and 20kV. The objective was to determine whether the materials studied were filled with inorganic particles.

### 2.4. Porosity

Porosity is a key parameter for foamed polymers, as it strongly impacts the mechanical properties of the material (e.g. density, compressive strength). To study it, the different samples were cut in the thickness direction. The new surface obtained was gently stamped on an ink pad
# PART 5. Study of the properties of three objects made of expanded polystyrene and comparison with foamed PLA

and then stamped on paper. The ink thus colours the cell walls, but not the bottom of the cells. Three samples were thus prepared for each material. Observations of the porosity of the samples were then made using a stereomicroscope (Leica MZ16 A). Four images were taken for each of the prepared samples. The 48 images obtained were then analysed by the FIJI software (ImageJ) which made it possible to measure the area of the various pores photographed in an automated manner. From this data, the number average diameter (d_m, µm), the size average diameter (d_s, µm), the polydispersity index (PDI), the cell density (N_c, cells.cm⁻³), and the cell wall thickness (δ, µm) were calculated (Julien et al., 2012).

## 2.5. Compression tests

The compression tests were carried out according to the standard NF EN 826 (Thermal insulating products for building applications — Determination of compression behaviour) and using an electromechanical testing systems (MTS Synergie 1000 RT). For this purpose, five samples of each of the materials were manufactured (L*1 = 20*20mm) and stored for 24 hours under controlled atmospheric conditions (T=23±5°C et Rh=50±5%).

To carry out the compression tests the samples were subjected to a preload of 250±10 Pa. The compression speed was 0.1*d/min, where *d* is the thickness of the sample in mm. The compression was carried out until 10% relative deformation was reached. From the curve obtained, the values of compressive strength (MPa), compressive modulus of elasticity (MPa) and yield stress were determined (MPa). In this way, five tests per type of sample were carried out.

# 3. Results and discussion

## 3.1.DSC

The glass transition temperature (Tg) of the different polystyrenes tested was between 105 and 107°C (Table 11). The transition temperature of the fish boxes was very slightly higher (107°C)
## PART 5. Study of the properties of three objects made of expanded polystyrene and comparison with foamed PLA

than that of the insulation plates and food cans. However, this difference is part of the variability of the Tg measurement. The Tg of unfoamed PLA was 60°C and that of foamed PLA was 63°C. Again, this difference in temperature can be explained by instrumental error, more than by the difference in structure between the two materials.

<table><caption>Table 11. Glass transition temperature (Tg) of the different materials tested.</caption><thead><tr><th></th><th>Insulated<br>EPS boxe</th><th>Insulation<br>plate</th><th>Food box</th><th>PLA<br>(pellets)</th><th>PLA foam</th></tr></thead><tbody><tr><th>Tg (°C)</th><td>107</td><td>105</td><td>105</td><td>60</td><td>63</td></tr></tbody></table>

### 3.2. SEM-EDX

Aluminium ions were observed in all samples analysed (
PART 5. Study of the properties of three objects made of expanded polystyrene and comparison with foamed PLA

Table 12). These are catalyst residues of Ziegler Natta type (Girois, 2013). In the case of the XPS boxes, Mg and Si ions were detected. It is possible that this detection is due to the presence of talc (Mg3Si4O10(OH)2), a mineral often used as an additive in plastics. Talc can be used as an additive in the form of nanoparticles. These particles produce flame-retardant effects such as a diffusion barrier (Lopez-Cuesta, 2016). For PLA the analysis does not show the presence of ions other than C, H and O.
PART 5. Study of the properties of three objects made of expanded polystyrene and comparison with foamed PLA

<table><caption>Table 12. Atomic percent (%).</caption><thead><tr><th></th><th>Mg</th><th>Al</th><th>Si</th></tr></thead><tbody><tr><td>Insulated EPS boxe</td><td>-</td><td>0.04±0.0</td><td>-</td></tr><tr><td>Insulation plate</td><td>-</td><td>0.09±0.01</td><td>-</td></tr><tr><td>Food box</td><td>0.04±0.0</td><td>0.06±0.04</td><td>0.09±0.02</td></tr><tr><td>Foamed PLA</td><td>-</td><td>-</td><td>-</td></tr></tbody></table>

### 3.3. Porosity

The *dn* of the insulated EPS box was on average slightly higher (84µm) than those of the insulation plate (74µm) and the food box (74µm) (Table 13). Nevertheless, the variability of the measurements from one measurement to another did not allow significant differences between the samples to be highlighted. The same applied in the case of size average diameter (*dw*) measurements. Indeed, the mean measured value of the insulated EPS box (153µm) was higher than that of the insulation plate (108µm) and the food box (106µm), but the variability of the measurements did not reveal any significant difference. As a result, the *PDI* of the different materials tested were very similar (0.6-0.7±0.1). The average cell density, however, was quite different. Thus, it was on average lower for the fish boxes (3351 cells/cm³) and slightly higher for the other two (5356 and 6801 cells/cm³). The difference was significant between the insulated box and the food box. The thickness of the pore walls was very similar from one type of material to another (about 600nm) and shows no significant variation. The ratio of width to length of the porosity is the same (0.6) regardless of the material studied. In
PART 5. Study of the properties of three objects made of expanded polystyrene and comparison with foamed PLA

the case of PLA, it is especially important to note that the pore size is significantly larger (dn=213±85 µm) than that of PS.

<table><caption>Table 13. Characteristics of the porosity.</caption><thead><tr><th></th><th>Number<br>average<br>diameter<br>(dn; µm)</th><th>Size<br>average<br>diameter<br>(dw, µm)</th><th>Polydispersity<br>index (PDI)</th><th>Cell<br>density<br>(Nc;<br>cells/cm³)</th><th>Cell wall<br>thickness<br>(δ; µm)</th><th>I/L ratio</th></tr></thead><tbody><tr><td>Insulated<br>EPS box</td><td>84±10</td><td>153±50</td><td>0.6±0.1</td><td>3351±1158</td><td>0.6±0.1</td><td>0.6</td></tr><tr><td>Insulation<br>plate</td><td>74±14</td><td>108±37</td><td>0.7±0.1</td><td>5356±2882</td><td>0.6±0.1</td><td>0.6</td></tr><tr><td>Food box</td><td>74±18</td><td>106±18</td><td>0.6±0.1</td><td>6801±1596</td><td>0.5±0.0</td><td>0.6</td></tr><tr><td>Foamed<br>PLA</td><td>213±85</td><td>250±-</td><td>0.9±-</td><td>83±-</td><td>83568±-</td><td>-</td></tr></tbody></table>

3.4.Compression tests

The study of the different materials revealed variations in the compression behaviour of the different materials (Table 14). Thus, insulation plates offered the highest compressive stress value (166kPa), followed by polystyrene in EPS boxes (128MPa). The third material (XPS) had the lowest average compressive stress value (58MPa). In terms of Young's modulus, a different ranking could be proposed. Insulation boards had the lowest Young's modulus (551 MPa), followed by XPS boxes (1,272MPa) and finally EPS boxes (3,962 MPa). Finally, in terms of mechanical threshold stress, the XPS boxes had the highest value (131 MPa). Next came the EPS boxes, with a value of the mechanical threshold stress of 93 MPa, and then the insulation
PART 5. Study of the properties of three objects made of expanded polystyrene and comparison with foamed PLA

plates (46 MPa). For PLA, due to the thinness of the material (<5 mm), it is not possible to measure these mechanical characteristics under compression. However, tensile test allows to determine the value of the young Modulus (1,059±138 MPa), i.e. similar to that of the polystyrene used in food trays.

<table><caption>Table 14. Mechanical properties of the materials.</caption><thead><tr><th></th><th>Property</th><th>Mean values</th></tr></thead><tbody><tr><td rowspan="3">Insulated EPS box</td><td>Compressive stress (MPa)</td><td>128±1</td></tr><tr><td>Young modulus (MPa; 10%)</td><td>3962±492</td></tr><tr><td>Mechanical threshold stress (MPa)</td><td>93±1.3</td></tr><tr><td rowspan="3">Insulation plate</td><td>Compressive stress (MPa)</td><td>166±20</td></tr><tr><td>Young modulus (MPa; 10%)</td><td>551±79</td></tr><tr><td>Mechanical threshold stress (MPa)</td><td>46±8</td></tr><tr><td rowspan="3">Food box</td><td>Compressive stress (MPa)</td><td>58±79</td></tr><tr><td>Young modulus (MPa; 10%)</td><td>1272±394</td></tr><tr><td>Mechanical threshold stress (MPa)</td><td>131±4</td></tr><tr><td rowspan="3">Foamed PLA</td><td>Compressive stress (MPa)</td><td>NA</td></tr><tr><td>Young modulus (MPa; 10%)</td><td>1059±138</td></tr><tr><td>Mechanical threshold stress (MPa)</td><td>NA</td></tr></tbody></table>
**4. Conclusion**

The results obtained show that in these few characteristics, foamed PLA has a certain capacity to replace PS in this type of use, but there are also limitations. Its lower Tg, for example, makes it more susceptible to loss of mechanical properties above about 60 degrees. This can be a problem for uses involving hot food. Beyond this example, it is clear that to replace PS in certain uses, thought must be given to the most suitable foamed PLA formulations. It is indeed possible to modulate the properties of the material according to the desired use. This aspect is however beyond the scope of this study.
## PART 6. Aging of foamed polylactic acid (PLA) in marine and atmospheric environments

Emeric Leluª, Mikaël Kedzierskiª, Gwénaël Le Maguerᵇ, Stéphane Bruzaudª

### Abstract

PLA foam has been identified by the OceanWise consortium as a potential replacement for polystyrene. To test the relevance of this material from an ageing point of view in the natural environment, samples were aged for 1 year in air and marine environments. The ageing of the PLA was then studied using a wide range of analytical tools and physico-chemical parameters. Thus, the carbonic index obtained by infrared spectrophotometry, porosity parameters, tensile tests and SEM images showed that PLA does not degrade well in the natural environment. From this point of view, it therefore seems of little relevance to replace PLA.

## 1. Introduction

Reaching a value of around 335 million tonnes in 2016, plastics production has never been so important in the world (PlasticsEurope, 2018). This exponential production is an illustration of our "plastic age". Plastics, because of their characteristics (e.g. low cost, insulating properties, impact resistance, durability), are part of our daily lives. They are synthetic organic polymers (such as polypropylene, polyethylene, polyvinyl chloride, polystyrene) with a very wide range of physico-chemical properties and therefore allow a wide choice of different end products. Unfortunately, a fraction (i.e. around 10% of annual production) of the plastic waste produced ends up in the natural environment. As a result, 60-80% of the waste discharged into the environment consists of plastics (Avio et al., 2017).

<footnote>ª IRDL UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France</footnote>

<footnote>ᵇ Archipel Institute, Université Bretagne Sud, 56100 Lorient, France</footnote>
In recent decades, it has become increasingly clear that it is necessary to be able to offer less environmentally damaging alternatives to the polymers most commonly used in our societies. This is the framework of the OceanWise project, supported by the European funding programme INTERREG Atlantic Area. This project specifically targets one of the polymers most commonly found in the natural environment: polystyrene. The project's ambition is therefore to propose solutions that allow the quantity of expanded (EPS) or extruded (XPS) polystyrene waste in the Atlantic to be reduced. OceanWise is a European project involving 13 partners from 5 different countries: Portugal, Spain, France, Ireland and the United Kingdom. This project aims to find concrete solutions to the problem of polystyrene waste. These solutions will take into account the whole life cycle of the object, and will integrate a transnational management of marine waste.

In this framework, the ageing of different objects made of polystyrene foam in sea water and in the atmosphere has been previously carried out. In order to finalise the project, it is necessary to test an alternative material to polystyrene in these same conditions. To do this, the OceanWise project consortium has identified polylactic acid (PLA), a polymeric material considered biodegradable in terrestrial environments, as a potential alternative (SEABIRD, 2020, 2019). Indeed, PLA is a biopolymer derived from renewable resources such as starch or sugar and is biodegradable under certain conditions, particularly in industrial compost. Its biodegradation capacity has an advantage in terms of environmental consequences and the recovery of plastic parts. PLA is used for the manufacture of food packaging (disposable tableware), for medical and automotive applications and, of course, for 3D printing.

However, while the ageing and biodegradation of PLA is relatively well known in terrestrial or industrial contexts, in the marine environment few studies have focused on it. Moreover, the particular case of ageing of PLA foams in the marine environment has never been studied. In
this context, our study proposes to acquire data on the ageing of foamed PLA in both air and
marine environments.

2. Materials and Methods

2.1. Polylactic acid

PLA is a semi-crystalline polymer with a temperature of melting of the crystalline phase around 175°C and a temperature glass transition of the amorphous phase around 60 °C. Prior to this study to obtain the expanded PLA, a single screw extruder from ThermoFisher Scientific and Scientific and a flat die 100 mm wide and 0.9 mm thick were used. The polymer and the additives (blowing agent, chain extender) are introduced into the hopper and then heated to a molten state. The process conditions were developed according to previous work (Julien et al., 2012).

2.2. Aging sites

The PLA samples were aged in an aerial environment on the roofs of the IRDL in connection
with a meteorological station measuring outdoor conditions, and in a marine environment at the
port of Kernevel. The samples for both environments were aged from January 2019 to January
2020.

2.2.1. Atmospheric ageing

For ageing in atmospheric conditions, the samples were placed placed in a polyethylene box on
the roof of the IRDL of the University of Southern Brittany in Lorient. A sample was taken
every two months.

2.2.2. Aging in marine environment

In the marine environment, the samples are immersed in a Japanese lantern-type net under a
floating dock at Kernevel, 3 km south of Lorient. These nets are used to protect the samples.
## 2.3. Meteorological conditions over the study period

Weather conditions were taken using a Vantage PRO 2 weather station (Davis Instruments). This station was installed according to the manufacturer's recommendations on the roof of the IRDL of the laboratory. Thanks to this instrument, we were able to measure precipitation with a resolution of 0.2 mm and an accuracy of ±4%, as well as temperature with a resolution of 0.1°C and an accuracy of 0.5°C. Solar radiation was measured with a precision pyrometer (resolution 1 W/m²; accuracy ±5%) over the wavelength range of 300 to 1100 nanometres. UV radiation was measured using a precision radiometer (resolution 0.1 MEDs; accuracy: ±8%) over a wavelength range between 290 and 390 nanometres.

Sea temperature measurements were taken using a Water Temp Pro v2 (HOBO) probe. This probe was placed in the net containing the samples. The temperature measurements were performed with a resolution of 0.02°C to 25°C and an accuracy of ±0.21°C. Weather data was collected throughout the aging period of the PLA from January 2019 to January 2020. Thus the total rainfall during this period was 692 mm with an average value of 53±37 mm/month (Figure 29). The highest rainfall was recorded in October 2019 with 143 mm and the lowest in July with only 1 mm. For marine aging, the water temperature varied between 9°C in February 2019 and 20°C in July, atmospheric temperatures varied from 7°C in January 2019 to 22°C in July 2019. The average minimum solar radiation is recorded in December (93 W/m²) and the average maximum solar radiation in July (601 W/m²) (Figure 30). The intensity of UV radiation is minimum in December (1.2*10⁻³ W/m²) and maximum from May to July (3.3 to 3.4*10⁻² W/m²).
<figure><img src="image_32.png" /><figcaption>Figure 29. Measurement of precipitation (mm) and marine and atmospheric temperatures (°C).</figcaption></figure>

<figure><img src="image_33.png" /><figcaption>Figure 30. Measurement of solar and UV radiations (W/m²).</figcaption></figure>

## 2.4. FTIR

The chemical characterization is carried out using a Fourier Transform Infrared spectrometer (ATR-FTIR Vertex70v, Bruker). For each sample, three different areas were analysed in order to calculate the average spectrum. The samples were recorded in absorbance mode in the 4000-800 cm⁻¹ region. The FTIR allows the characterisation of the chemical ageing of the samples.
The carbonyl index (CI) of the samples was calculated according to the following equation (Janczak et al., 2018):

$$CI = 1740A / 1450A \ (Equation \ 9)$$

## 2.5. Porosity

Porosity is an important factor as it has an impact on the mechanical properties of the material.

To study it, the samples were cut in the thickness direction using a scalpel and then, using a stamp, they were covered with black ink. This procedure makes it possible to obtain a contrast that brings out the porosity. This latter was then observed using a stereomicroscope (Leica MZ16 A). For each sample, 8 to 10 images were taken and analysed using the free FIJI software (Figure 31).

<figure><img src="image_34.png" /><figcaption>Figure 31. Optical microscope image of PLA aged 6 months in the atmosphere and artificially coloured black to highlight changes in geometry.</figcaption></figure>
PART 6. Aging of foamed polylactic acid (PLA) in marine and atmospheric environments

Thus, for each image, the surface area ($A_i$) of each cell was measured, which makes it possible to calculate the equivalent diameter of each cell ($d_i$) (eq. 10). Only the cells completely included in the mask were taken into account, cropped by the edges of the samples or which are intersected by the mask were not measured. Thus, the larger the cells were, the higher their probability of crossing the edge of the sample, which means that the number of large cells were underestimated. To solve this problem, the correction method for the measurement mask developed by Miles and Lantuejoul (Avérous et al., 1995) was applied. Thus, the calculated inclusion probability $p_i$ (eq. 11) allowed to correct this problem and to obtain the diameter of the cells. Thus, for each image, each cell was measured and the average diameter determined ($d_n$, µm; eq. 12).

$$d_i = 2\sqrt{\frac{A_i}{\pi}} \quad (\text{Equation 10})$$

$$p_i = \frac{(z_x - L_x)(z_y - L_y)}{z_x z_y} \quad (\text{Equation 11})$$

$$\overline{d_n} = \frac{\sum \left( \frac{d_i}{p_i} n_i \right)}{\sum \left( \frac{1}{p_i} \right)} \quad (\text{Equation 12})$$

## 2.6. Tensile test

The tensile tests were carried out on a MTS Synergie 1000 RT electromechanical testing system which will provide the Young's modulus of stress and displacement during the test. The tensile test is the most common physical experiment used to characterise the mechanical behaviour of a material. Each end of the specimen is clamped in jaws, a displacement is then exerted and the resulting force applied to the material is measured until the specimen breaks or does not break. Tensile tests are carried out using an MTS Synergie 1000 RT electromechanical testing system.
# PART 6. Aging of foamed polylactic acid (PLA) in marine and atmospheric environments

For each sample, 5 tests are carried out in order to be able to average the results. To carry out the tests, a plate of L * 1 = 90 * 15 mm is cut out. The tests are carried out until failure, for which a 250 N cell is used.

## 2.7. Scanning electronic microscope (SEM-EDX)

In order to image the ageing of the samples, their surfaces were analysed using a scanning electron microscope (JSM-IT500HR). This observation technique is based on the detection of secondary electrons emerging from the surface under the impact of a primary electron beam that scans the surface being observed. The SEM will provide a visual record of the degradation that the material undergoes over time, but will also make it possible to observe the presence of microorganisms that develop or attach themselves to the PLA. The SEM is coupled with EDX energy dispersion spectrometry allowing a mapping of the chemical composition of the surface examined (mineral/metallic charges or elements).

# 3. Results

## 3.1. FTIR

The carbonyl index makes it possible to monitor chemical ageing. In the air and in a marine environment, it tended to decrease until the 8th month: from a value of 2.71 ± 0.07 for the non-aged sample, it decreased to a value of 1.12 ± 0.81 in water and 1.75 ± 0.46 in air (Figure 32). After the 8th month (September) an increase was observed in air and sea. The CI in the air increased slightly to 2.73 ±0.02, the CI in the sea also increased but more suddenly to a value of 7.25 ± 0.76.
<figure><img src="image_35.png" /><figcaption>Figure 32. Evolution of carbonyl indices of samples aged 1 year in marine and air environments.</figcaption></figure>

## 3.2. Porosity

In the atmosphere, the average *dn* of the unaged PLA (
# PART 6. Aging of foamed polylactic acid (PLA) in marine and atmospheric environments

Table 15) was 213 µm, then it decreased until the 12th month in the atmosphere to reach 133 µm, except for the sample aged 8 months which was higher than the unaged one (232 µm). The *dn* of the samples aged in the marine environment (table 2) decreased over time, from 213 µm for the unaged samples to 147 µm for the 12th month, but with the exception, however, of the *dn* measurements of the 8th and 10th month (319 µm and 227 µm respectively).
<table><caption>Table 15. Evolution of the dn for PLA samples aged in atmospheric and marine environment.</caption><thead><tr><th>Time<br>(Month)</th><th>Atmospheric environment<br>(dn, µm)</th><th>Marine environment<br>(dn, µm)</th></tr></thead><tbody><tr><td>0</td><td>213±85</td><td>213±85</td></tr><tr><td>2</td><td>163±43</td><td>158±51</td></tr><tr><td>4</td><td>164±53</td><td>188±63</td></tr><tr><td>6</td><td>166±78</td><td>171±41</td></tr><tr><td>8</td><td>232±96</td><td>319±99</td></tr><tr><td>10</td><td>153±50</td><td>227±55</td></tr><tr><td>12</td><td>133±65</td><td>147±49</td></tr></tbody></table>

The next figure compares the number of average diameters of air-aged and sea-aged samples (Figure 33). It can be noted that the *dn* of PLA aged in a marine environment was slightly higher than that of the marine environment during ageing, however it remains fairly constant during the ageing process for both environments. At the 8th month an increase can still be noted for both ageing environments. However, it was immediately followed at the 12th month by a decrease.
<figure><img src="image_36.png" /><figcaption>Figure 33. Evolution of the number of mean diameter as a function of time for samples aged in air and sea environments.</figcaption></figure>

### 3.3. Tensile test

The young modulus of unaged PLA is 1059 MPa (Table 16), we notice that there is no significant change over time, the minimum is found in the 10th month with 903 MPa. Regarding the stress at break, it is the same with 18.3 MPa for the unaged and 12.6 MPa for the 10th month, this does not represent a difference. In terms of deformation, the same situation was observed with 2.9% for the unaged one and 2.2% for the 10th month. Thus, the deformations do not show any real difference during ageing.

<table><caption>Table 16. Evolution of the young modulus, stress at break, strain at break during air aging.</caption><thead><tr><td>Air environment</td><td>Young's Modulus (MPA)</td><td>Stress at break (MPA)</td><td>Deformation at break (%)</td></tr></thead><tbody><tr><td>Not aged</td><td>1059 ± 138</td><td>18,28 ± 0,65</td><td>2,92 ± 0,52</td></tr><tr><td>Aged 2 months</td><td>1030 ± 35</td><td>17,92 ± 0,94</td><td>2,72 ± 0,11</td></tr><tr><td>Aged 4 months</td><td>951 ± 53</td><td>14,60 ± 0,40</td><td>2,43 ± 0,12</td></tr><tr><td>Aged 6 months</td><td>979 ± 45</td><td>14,98 ± 1</td><td>2,48 ± 0,16</td></tr><tr><td>Aged 8 months</td><td>982 ± 54</td><td>14,70 ± 0,80</td><td>2,38 ± 0,2</td></tr><tr><td>Aged 10 months</td><td>903 ± 18</td><td>12,56 ± 0,41</td><td>2,17 ± 0,14</td></tr><tr><td>Aged 12 months</td><td>986 ± 15</td><td>14,94 ± 0,86</td><td>2,3 ± 0,24</td></tr></tbody></table>
PART 6. Aging of foamed polylactic acid (PLA) in marine and atmospheric environments

The next table shows the evolution of Young's modulus, tensile strength, and ultimate tensile stress of PLA aged in sea water (Table 17). There was no significant change in Young's modulus, except for the 6th and 10th month, with a slightly lower modulus of 878 MPa and 815 MPa for 1059 MPa respectively for the unaged sample. The stress at break was 18.3 MPa for the unaged sample and the minimums were also in the 6th and 10th month with 13.0 MPa and 16.2 MPa, there was no real difference. In the case of deformations at rupture, the test also showed no significant differences apart from a slight decrease for the 10th month (1.9% deformation compared to 2.9% for the non-aged).

<table><caption>Table 17. Evolution of the young modulus, stress at break, strain at break during marine aging.</caption><thead><tr><th>Marine environment</th><th>Young's Modulus (MPA)</th><th>Stress at break (MPA)</th><th>Deformation at break (%)</th></tr></thead><tbody><tr><td>Not aged</td><td>1059 ± 138</td><td>18,28 ± 0,65</td><td>2,92 ± 0,52</td></tr><tr><td>Aged 2 months</td><td>989 ± 49</td><td>16,24 ± 0,56</td><td>2,56 ± 0,25</td></tr><tr><td>Aged 4 months</td><td>960 ± 32</td><td>15,60 ± 2,90</td><td>2,24 ± 0,56</td></tr><tr><td>Aged 6 months</td><td>878 ± 24</td><td>12,96 ± 0,72</td><td>2,38 ± 0,16</td></tr><tr><td>Aged 8 months</td><td>966 ± 44</td><td>16,22 ± 1,21</td><td>2,304 ± 0,25</td></tr><tr><td>Aged 10 months</td><td>815 ± 40</td><td>11,16 ± 1,34</td><td>1,951 ± 0,31</td></tr><tr><td>Aged 12 months</td><td>966 ± 51</td><td>15,38 ± 1,50</td><td>2,35 ± 0,40</td></tr></tbody></table>

By comparing the young modulus of the PLA aged in the air and in the sea (Figure 34), one notices in view of the standard deviations no real decrease in the young modulus over time for the 2 media. The young modulus between the 2 environments have no real difference except for the 6th and 10th months, the young modulus of the marine environment is slightly lower than that of the air environment.
# PART 6. Aging of foamed polylactic acid (PLA) in marine and atmospheric environments

<figure><img src="image_37.png" /><figcaption>Figure 34. Evolution of the young modulus as a function of time for samples aged in air and sea environments.</figcaption></figure>

## 3.4. Scanning electronic microscope (SEM-EDX)

The SEM images show the surface of unaged PLA (a), and aged 6 (b), 10 (c), 12 (d) months in an air environment (Figure 35). SEM observations of PLA samples aged in an atmospheric environment show no difference from the reference sample.
<figure><img src="image_38.png" /><figcaption>Figure 35. Observation under a scanning electron microscope of (a) unaged PLA (b) aged 6 months in air environment (c) aged 10 months in air environment (d) aged 12 months in air environment.</figcaption></figure>

Samples aged in a marine environment (Figure 36) had a different surface appearance from samples aged in an atmospheric environment. Indeed, they had many deposits that come from mineral salts and microalgae present in the sea. Even on some samples, diatoms were observed, which are microorganisms present in the sea. However, we observe a greater deposit on the PLA aged 6 months (Figure 36a) than on those aged 10 months and 12 months. Significant cracks are present on the sample aged 12 months (Figure 36b) which are not observed over the same aging time in an air environment.
<figure><img src="image_39.png" /><figcaption>Figure 36. Observation under a scanning electron microscope of (a) PLA aged 6 months in marine environment (b) aged 10 months in marine environment (c) aged 12 months in marine environment with 500 µm.</figcaption></figure>
## 4. Discussion and conclusion

According to the results, aging in an atmospheric or marine environment has no real impact on the mechanical properties of PLA, which showed two main points:

* it confirms that PLA does not have the ability to biodegrade in marine environments.

* It can be used for exterior applications without great loss of mechanical properties

Thus, these results show that PLA can be used for applications in contact with seawater during one year without an important loss of mechanical properties.

The counterpart of these observations is that PLA, even foamed, does not seem to be a good candidate for the OceanWise project. PHA is a polymer known for its biodegradability and could be another potential candidate for replacement of PS. New foaming methods have been developed in recent years and since 2020 this type of foamed polymer has started to be commercialised.
Reference

Avérous, L., Quantin, J.C., Lafon, D., Crespy, A., 1995. Granulometric Characterization of Short Fiberglass in Reinforced Polypropylene. Relation to Processing Conditions and Mechanical Properties. Int. J. Polym. Anal. Charact. 1, 339–347.
https://doi.org/10.1080/10236669508233886

Avio, C.G., Gorbi, S., Regoli, F., 2017. Plastics and microplastics in the oceans: From emerging pollutants to emerged threat. Mar. Environ. Res. 128, 2–11.
https://doi.org/https://doi.org/10.1016/j.marenvres.2016.05.012

Janczak, K., Hrynkiewicz, K., Znajewska, Z., Dąbrowska, G., 2018. Use of rhizosphere microorganisms in the biodegradation of PLA and PET polymers in compost soil. Int. Biodeterior. Biodegradation 130, 65–75.
https://doi.org/https://doi.org/10.1016/j.ibiod.2018.03.017

Julien, J.-M., Bénézet, J.-C., Lafranche, E., Quantin, J.-C., Bergeret, A., Lacrampe, M.-F., Krawczak, P., 2012. Development of poly(lactic acid) cellular materials: Physical and morphological characterizations. Polymer (Guildf). 53, 5885–5895.
https://doi.org/https://doi.org/10.1016/j.polymer.2012.10.005

PlasticsEurope, 2018. Plastics - the Facts 2018.
# Part 7. Assessment of biodegradation in seawater at the sediment-water interface

Mikaël Kedzierski<sup>b</sup>, Gwénaël Le Maguer<sup>c</sup>, Stéphane Bruzaud<sup>b</sup>

## 1. Introduction

The evolution of the PLA foam samples showed little change as it aged in the marine environment, indicating a low capacity to degrade in this type of environment. In an attempt to confirm these initial observations, a laboratory test was carried out by the Regional Institute of Advanced Materials (Institut Regional des Materiaux Avancés). The aim of this test was in particular to better measure one of the ageing pathways of the materials studied: the biodegradation. To do this, the methodology used is based on the recommendations of the standards dedicated to measuring the rate of biodegradation in the marine environment.

## 2. Material and methods

### 2.1. *Samples presentation*

Two samples were submitted to this study. Both have been provided by the IRDL. Sample will be named as PLA foam and PLA-PBAT. Carbon analysis has been running onto the samples to determine the quantity to expose to the seawater for biodegradation purpose. PLA foam and PLA-PBAT are respectively composed of 50,16% and 50,88% of carbon.

Cellulose, ashless paper Whatman 42, is used as positive control.

<footnote><sup>a</sup> Institut Regional des Materiaux Avancés, 56270 Ploemeur</footnote>

<footnote><sup>b</sup> Institut de Recherche Dupuy de Lôme, UMR CNRS 6027, Université Bretagne Sud, 56100 Lorient, France</footnote>

<footnote><sup>c</sup> Archipel Institute, Université Bretagne Sud, 56100 Lorient, France</footnote>
Seawater has been taken at *Le Perello*, Morbihan, France.

## 2.2. Method

Method used to determine biodegradation rate in seawater is based on the normative document NF EN ISO 19679. This method relies on the quantification of CO₂ produced during the biodegradation process. Experimentation was performed at 25°C in hermetic conditions allowing the produced CO₂ to be measured without interference with atmospheric CO₂. A negative control is also set up to subtract CO₂ produced in absence of sample to those produced when the sample is exposed to microorganisms.

CO₂ is trapped into a sodium hydroxide solution and then is quantified by back dosing method with hydrochloric acid.

Measurements were carried out for 133 days.

## 3. Results

According to ISO/FDIS 22403, ISO/FDIS 22404 and ASTM D 7081, biodegradation rate of positive control (cellulose reference) should be superior to 60% after 180 days, which is observed in both experimentations. Moreover, sample should reach a relative 90% biodegradation rate in comparison to the reference.

Regressions are obtained with Datafit software using Hills equation (3 constants) for cellulose and Boltzmann double sigmoid equation for PLA-PBAT and PLA-foam (Table 18 & Table 19).
This difference in used equations is due to graphics particularities for PLA-foam and PLA-PBAT samples which show two plateaus (Figure 37 & Figure 38).
<table><caption>Table 18. Extrapolation using Hills (3 constants).</caption><thead><tr><th colspan="2">y = ax<sup>b</sup>/(c<sup>b</sup> - x<sup>b</sup>)</th></tr><tr><td colspan="2">with y = % biodegradation, x = number of incubation days, a = value of biodegradation asymptote, b = slope coefficient, c = time (in days) to reach half the maximum biodegradation value</td></tr><tr><th>Tested material</th><th>Cellulose</th></tr></thead><tbody><tr><td>Coefficient a</td><td>73,450</td></tr><tr><td>Coefficient b</td><td>3,283</td></tr><tr><td>Coefficient c</td><td>18,036</td></tr><tr><td>Validity (in days)</td><td>0 ≤ x ≤ 133</td></tr><tr><td>R<sup>2</sup></td><td>0,981</td></tr><tr><td>Cellulose validity</td><td>Reach 70% after 45 days : OK</td></tr></tbody></table><table><thead><tr><th colspan="2">Extrapolation using Boltzmann double sigmoid</th></tr><tr><td colspan="2">Y = A2*((p/(1+10^((x1-x)*h1)))+(1-p)/(1+10^((x2-x)*h2))))</td></tr><tr><td colspan="2">with y = % biodegradation, x = number of incubation days, A2 = value of biodegradation asymptote, p = proportion in % of first plateau, h1 and h2 = slope coefficient, X1 and X2 = time (in days) to reach half the maximum biodegradation value for plateau 1 and plateau 2</td></tr><tr><th>Tested material</th><th>PLA foam</th></tr></thead><tbody><tr><td>Coefficient A2</td><td>10,657</td></tr><tr><td>Coefficient h1</td><td>1,295</td></tr><tr><td>Coefficient h2</td><td>0,069</td></tr><tr><td>Coefficient P</td><td>0,535</td></tr><tr><td>Coefficient X1</td><td>21,362</td></tr><tr><td>Coefficient X2</td><td>104,208</td></tr><tr><td>Validity (in days)</td><td>0 ≤ x ≤ 133</td></tr><tr><td>R<sup>2</sup></td><td>0,994</td></tr><tr><td>PLA foam validity</td><td>Reach 90% relative biodegradation compare to cellulose at the end of test : NO</td></tr></tbody></table>
Part 7. Assessment of biodegradation in seawater at the sediment-water interface

<figure><img src="image_40.png" /><figcaption>Figure 37. Biodegradation rate of PLA foam in marine environment</figcaption></figure>