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LCA
LABORATOIRE DE CHIMIE
AGRO-INDUSTRIELLE

INFLUENCE OF DEW RETTING DURATION ON THE
CHARACTERISTICS
OF FIBRES EXTRACTED FROM LINSEED FLAX STRAW FOR
LOAD BEARING APPLICATION

Saif Ullah Khan<fnref n="1" />,<fnref n="2" />, Laurent Labonne<fnref n="1" />, Philippe Evon<fnref n="1" />, Pierre Ouagne<fnref n="2" />

* E-mail address (presenting author): skhan@enit.fr (Saif Ullah Khan)

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LCA Laboratoire de Chimie Agro-Industrielle

CONTENT

* Introduction

* Fibre extraction

* Fibre characterization

* Conclusion

* Future work

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<footnote n="1">¹ Laboratoire de Chimie Agro-industrielle (LCA), INRAE, INPT, Toulouse, France</footnote>

<footnote n="2">² Laboratoire Génie de Production, INPT, Tarbes, France</footnote>
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Laboratoire de Chimie Agro-Industrielle

# GEOTEXTILES

## Geotextile Functions

Separation

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SEPARATION (S)

Filtration

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FILTRATION (F)

Reinforcement

Protection

Drainage

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REINFORCEMENT (R)

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PROTECTION (P)

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Reference: https://www.lonrace.com/What-is-geotextile-id19602.html

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Laboratoire de Chimie Agro-Industrielle

# GEOTEXTILE REINFORCEMENT

<figure><img src="image_11.png" /><figcaption>Figure 7. Reinforcement function of geotextiles.</figcaption></figure>

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Reinforcement geotextiles a) slope reinforcement b) reinforcement of embankment c) soft soil reinforcement foundation d) reinforcement of load transfer platform
Reference: (Hao wu et al, 2020)

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Laboratoire de Chimie Agro-Industrielle

## INTRODUCTION

* Natural fibres got attraction over synthetic fibres due to environmental concerns (Ghosh et al. 2009)

* Three main crops (hemp, textile flax and linseed flax) are mostly cultivated crops in Europe.

* In France, hemp is cultivated on 16,700 ha whereas linseed flax is cultivated on 26,000 ha (Carus et al. 2016; Le Ravalec et al. 2020).

* Hemp is used for geotextile applications but not linseed flax.

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Laboratoire de Chimie Agro-Industrielle

## INTRODUCTION

* Two types of flax: textile flax and linseed flax

* Textile flax is cultivated for its fibres (mostly used for clothing).

* Linseed flax is cultivated for seeds (vegetable oil and protein fraction) and its straws are considered as burden, and they are burnt or used as animal litter.

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## INTRODUCTION

* Highly branched plant with a height around 40-60 cm.

* Its straws are easily available.

* Straws consist of shives (woody part) and fibers.

* Main application of linseed flax straws is limited to animal litter and for insulation.

* Extracted fibres will be used for load bearing applications.

* Also, around 60-65 % mass of straws is shives so it is important to utilize them in a better way as well.

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## LINSEED FLAX FIELD

Flowering

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Seed maturity

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Beginning of retting

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Collection of straws

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Laboratoire de Chimie Agro-Industrielle

# PICTORIAL REPRESENTATION OF FLAX

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Reference: (Zhu et al, 2013)

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# RETTING

* Retting is performed to dissolve the pectins binding the fibres together and to the shives. It contributes to ease the fibre extraction and separation.

* Types of retting are:

1. Dew retting

2. Water retting

3. Enzyme retting

4. Chemical retting

5. Mechanical retting

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## HARVESTING DETAILS AND RETTING DURATION OF BATCHES

<table><thead><tr><td>Batch number</td><td>Harvesting year</td><td>Retting duration (weeks)</td></tr></thead><tbody><tr><td>1</td><td>2018</td><td>0</td></tr><tr><td>2</td><td>2018</td><td>2</td></tr><tr><td>3</td><td>2019</td><td>12</td></tr><tr><td>4</td><td>2019</td><td>14</td></tr></tbody></table>

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## MANUAL EXTRACTION OF FIBERS FROM STRAWS

<table><thead><tr><td>Batch number</td><td>Fiber content (%)</td><td>Shives and dust content (%)</td></tr></thead><tbody><tr><td>1</td><td>28.9</td><td>71.1</td></tr><tr><td>2</td><td>32.2</td><td>67.8</td></tr><tr><td>3</td><td>30.4</td><td>69.6</td></tr><tr><td>4</td><td>28.8</td><td>71.2</td></tr></tbody></table>

* Fibre content varied from 29% to 32% for different batches and it is independent of dew retting duration.

* This fibre content inside dry mass of straws is significant.

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## CHEMICAL COMPOSITION OF FIBRES

* Fibres were cut and then grinded into a powder.

* ADF and NDF attacks were performed to determine the percentage of hemicelluloses, cellulose and lignins.

* The method from Blumenkrantz et al. (1973) was used to determine the pectin content inside bast fibers.

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## CHEMICAL COMPOSITION OF FIBRES

<table><thead><tr><td>Dew retting duration (weeks)</td><td>Hemicelluloses (% dry mass)</td><td>Lignins (% dry mass)</td><td>Cellulose (% dry mass)</td><td>Pectins (% dry mass)</td></tr></thead><tbody><tr><td>0</td><td>12.9±0.5</td><td>5.3±0.4</td><td>62.1±0.4</td><td>4.4±0.2</td></tr><tr><td>2</td><td>6.6±0.1</td><td>7.2±0.4</td><td>65.5±0.4</td><td>4.4±0.1</td></tr><tr><td>12</td><td>8.0±0.4</td><td>3.6±0.3</td><td>73.9±0.6</td><td>3.0±0.3</td></tr><tr><td>14</td><td>6.8±0.4</td><td>3.8±0.2</td><td>75.7±0.4</td><td>2.7±0.3</td></tr></tbody></table>

* With increase in dew retting duration, pectin content is decreased and cellulose content is increased at the same time.

* Decrease in pectin content favors the fibre extraction and fibre separation.

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## FIBRE EXTRACTION PROCESS

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## PURITY OF FIBRE MATERIAL

<table><thead><tr><td>Batch number</td><td>Fibre purity (%w/w)</td><td>Fibre yield (%, in proportion to the initial mass of fibres)</td></tr></thead><tbody><tr><td>1 (No dew retting)</td><td>67</td><td>79%</td></tr><tr><td>2 (2 weeks dew retting)</td><td>85</td><td>Not determined</td></tr><tr><td>3 (12 weeks dew retting)</td><td>82</td><td>Not determined</td></tr><tr><td>4 (14 weeks dew retting)</td><td>73</td><td>90%</td></tr></tbody></table>

* Fibre purity varied from 67% to 85% depending on the batch.

* Whereas fibre yield varied from 79% to 90% for batch number 1 to batch number 4.

* With increased dew retting duration, fibre yield was found to be increased.
## FIBRE BUNDLE LENGTH OF ALL BATCHES

<table><thead><tr><td>Batch number</td><td>Length of fibre bundle (cm)</td></tr></thead><tbody><tr><td>1</td><td>10.9±5.9</td></tr><tr><td>2</td><td>11.1±5.3</td></tr><tr><td>3</td><td>13.1±7.1</td></tr><tr><td>4</td><td>12.8±7.0</td></tr></tbody></table>

* Longer fibre bundles as compared to previous work by Ouagne et al. (2017) in which fibre bundle length range was from 3.7 cm to 5.3 cm.

* This mechanical extraction process (breaking card instead of "all fibre" extraction device) is more suitable for longer fibre bundles.

* Better preserved fibre bundle length with increased dew retting duration.

## TENSILE PROPERTIES (DIASTRON MACHINE)

* The Diastron fibre testing

* Elementary fibre samples preparation

* Diameter measurements (right end of machine)

* Tensile properties determination

* Results are presented as mean values ± standard deviations.

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DIAMETER AND CROSS SECTIONAL AREA

<table><thead><tr><td>Batch number</td><td>Retting duration (weeks)</td><td>Minimum diameter (μm)</td><td>Maximum diameter (μm)</td><td>Cross sectional area (μm²)</td></tr></thead><tbody><tr><td>1</td><td>0</td><td>13.5</td><td>26.2</td><td>323.3</td></tr><tr><td>2</td><td>2</td><td>10</td><td>28.2</td><td>243.3</td></tr><tr><td>3</td><td>12</td><td>11.6</td><td>22</td><td>180.8</td></tr><tr><td>4</td><td>14</td><td>10.8</td><td>27.7</td><td>240.9</td></tr></tbody></table>

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MINIMUM DIAMETER, MAXIMUM DIAMETER AND CROSS SECTIONAL AREA

* Cross sectional area for all the batches ranged from 181 µm² to 323 µm².

* It corresponds to diameters of 15-20 µm.

* So, it is reasonable to assume that the manually extracted fibres are indeed individual ones.

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LCA

Laboratoire de Chimie Agro-Industrielle

TENSILE STRENGTH OF ALL BATCHES

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ELASTIC MODULUS OF ALL BATCHES

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Laboratoire de Chimie Agro-Industrielle

ELASTIC MODULUS OF ALL BATCHES

❖ Elastic modulus varies from 40.9 to 56.5 GPa

❖ The more the tensile strength, the more the elastic modulus.

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Laboratoire de Chimie Agro-Industrielle

YARN PRODUCTION

100% linseed flax fibre's yarns were manufactured by gille spinning machine

Tex of the yarn was calculated by measuring the weight in grams in 1000 m length of the yarn and we achieved around 4 ktex yarns.

* Obtained yarns are good for geotextile applications with strength of around 47 MPa and diameter of 2.98 mm

* Whereas for hemp (45 MPa with 4312 tex), for flax (72 MPa with 4187 tex) and for coir (14 MPa with 6172 tex) (Ouagne et al, 2017)

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## CONCLUSION

* Bast fibers are 30% (w/w) inside linseed flax straw: compatible with industrial projection.

* Dew retting on the field plays important role in chemical composition (decrease in pectin content, and increase in cellulose content), ease of fibre extraction, and tensile strength values.

* A 12 weeks dew retting duration has been identified as the optimum.

* Increased fibre length is achieved by this process which is helpful in yarn manufacturing.

* Tensile strength and elastic modulus of linseed flax fibers are in the 700-922 MPa range and around 41-57 GPa, respectively.

* From the optimal extracted fibers, 100% linseed flax fiber-based yarns were produced with controlled tex values.

* It could permit to reduce the mass of fibres for similar mechanical functions.

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Laboratoire de Chimie Agro-Industrielle

## FUTURE WORK

* To analyze the service life of these yarns through biodegradation protocols.

* Coating treatments using (i) chitosan or (ii) linseed oil was done to preserve for longer time the use of yarns in geotextile applications;

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ADDITIONAL RESULT FROM SHIVES

* Shives are converted into fibre boards by twin-screw extruder process (research article already published in JoVE).

* **Title:** Twin-Screw Extrusion Process to Produce Renewable Fiberboards

* Journal of Visualized Experiments (JoVE)

* DOI: 10.3791/62072

* Published date: January 22, 2021

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THANK YOU...

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DO YOU HAVE ANY QUESTIONS ?

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