# 3D printing of biodegradable biocomposites based on forest industrial residues by fused deposition modeling

Sarra Helaoui, Ahmed Koubaa, Hedi Nouri, Martin Beauregard, Sofiane Guessasma

► To cite this version:

Sarra Helaoui, Ahmed Koubaa, Hedi Nouri, Martin Beauregard, Sofiane Guessasma. 3D printing of biodegradable biocomposites based on forest industrial residues by fused deposition modeling. Industrial Crops and Products, 2024, 222 (4), pp.119799. 10.1016/j.indcrop.2024.119799. hal-05078774

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Submitted on 22 May 2025

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# 3D printing of biodegradable biocomposites based on forest industrial residues by fused deposition modeling

Sarra Helaoui<sup>a,b</sup>, Ahmed Koubaa<sup>a</sup>, Hedi Nouri<sup>b</sup>, Martin Beauregard<sup>a</sup>, Sofiane Guessasma<sup>c,∗</sup>

## ARTICLE INFO

### Keywords:

- Biocomposites

- Additive manufacturing

- Biodegradable

- Forest industrial residues

- Fused deposition modeling

## ABSTRACT

This study investigated the impact of industrial forest residues (IFR) type and proportion on 3D-printed biocomposites (BC). Fused deposition modeling (FDM) produced BC containing up to 20 % Jack pine sawdust, wood ashes, cellulose fibers, and polylactic acid (PLA). The BC thermal stability, surface chemistry, microstructure, and physical and mechanical were investigated. Thermal stability investigations revealed that adding IRF resulted in a decline in the PLA degradation temperature, an increase in the residual mass, a decrease in the glass transition temperature, and an improvement in crystallinity. Add IRF to PLA showed an important reduction in ductility, a consistent reduction of the tensile and flexural strengths with increasing proportion but only a slight or a non-significant reduction the modulus of elasticity. Adding forest waste filler to pure PLA increased the water absorption (WA) and dimensional accuracy (TA) of the biocomposites, which was expected due to the hydrophilic character of fillers. The microstructural analysis demonstrated that a higher filler level resulted in a greater porosity, roughness, and visible filler pull-out on the filament and printed parts surfaces. Surface chemistry analysis suggested poor interactions between the PLA and the fillers and consequently poor interfacial adhesion. Furthermore, the rheological investigations confirmed that the complex viscosity and storage modulus of PLA-Jack pine's sawdust and PLA-cellulose fibers increased with filler. In contrast, the PLA-wood ashes showed opposite results. Using 3D-printed biodegradable biocomposites provided a sustainable option for reducing dependence on non-renewable plastic, valorizing the value chain of forest products, and promoting the circular economy.

## 1. Introduction

Additive manufacturing (AM) revolutionized the manufacturing industry due to its ability to create complex and personalized designs, structures, and customized prototypes (Jagadeesh et al., 2022). Its efficiency in material usage and the elimination of post-processing steps resulted in reduced manufacturing time, waste, and cost (Al-Ketan et al., 2021). Fused Deposition Modeling (FDM) has emerged as a promising technique for producing biocomposites and a sustainable alternative to traditional methods. FDM is widely utilized due to its low cost and ease of operation compared to other AM techniques. This method involved the extrusion of polymer filaments through a nozzle, layer by layer, to create three-dimensional objects.

The use of biosourced feedstocks for AM is justified because the

excessive use of petroleum-based plastic has caused serious depletion of landfill capacities and has caused significant damage to the environment. As a response, there has been a growing interest in developing biodegradable alternatives to replace traditional non-renewable plastics. Polylactic acid (PLA), a fully biodegradable polymer used in AM, is derived from microbial synthesis of monomers with high enantiomeric purity and yield. PLA has emerged as a highly attractive material due to its physical properties, renewable nature, compatibility, and cost-effectiveness. It is widely available and easily processable, which can be modified with functional groups or fillers to enhance its performance. In addition, composites made of PLA and natural fibers decomposed naturally without any ecological concerns (Rajeshkumar et al., 2021). PLA has found numerous applications in technology and engineering, making it a key material for future sustainable manufacturing processes

<footnote><sup>a</sup> UQAT, Université du Québec en Abitibi-Témiscamingue, 445, boul. de l'Université, Rouyn-Noranda, QC J9X 5E4, Canada</footnote>

<footnote><sup>b</sup> Laboratory of Electromechanical Systems (LASEM), National Engineering School of Sfax, University of Sfax, Sfax 3038, Tunisia</footnote>

<footnote><sup>c</sup> INRAE, UR 1268 Biopolymères Interactions Assemblages, Équipe Paroi Végétale et Polymères Pariétaux, Site de la Géraudière BP71627, Cedex 03, Nantes 44316, France</footnote>

<footnote>* Corresponding author.
E-mail address: sofiane.guessasma@inrae.fr (S. Guessasma).</footnote>
(Wróblewska-Krepsztul et al., 2018). It presents a low melting temperature, rendering it highly suitable for 3D printing as a matrix with natural fibers (Cuiffo et al., 2017). Nonetheless, its high brittleness, poor thermal resistance, and low crystallization kinetic have restricted its application (Ren et al., 2016). Several contributions focused on blending PLA with different biosourced fillers to mitigate the lack of PLA performance.

The forest industry generates a significant amount of industrial forest residues (IFR) and thus can be regarded as a promising filler supplier for AM. IFRs were usually incinerated or disposed of, incurring high costs for the industry. Only a small portion of IFR was currently being utilized for non-energy purposes. With its abundance, affordability, renewability, and sustainability, forest residues can be a valuable source of raw materials for other applications (Sang et al., 2019). They have gained attention as a cost-effective source of lignocellulosic material for producing 3D-printed wood composites to improve the value chain of forest products and minimize their negative environmental impact.

There has been a growing interest in wood-plastic composites (WPC) reinforced with natural fibers due to their environmental and economic benefits. Recent studies have focused on incorporating lignocellulosic, cellulose, and lignin reinforcement into PLA to enhance its mechanical and thermal properties (Tanase-Opedal et al., 2019; Tablit et al., 2024). These materials allow valorizing of forest (Awad et al., 2023), agricultural (Cali et al., 2020; Kumar and Das, 2017), or marine waste (Scaffaro et al., 2018), resulting in products with final properties suitable for various applications. The utilization of biocomposites in 3D printing has gained significant attention due to their potential to create a sustainable and eco-friendly product that offers a cost-effective and environmentally friendly solution for material production (Awad et al., 2023; Shahar et al., 2022).

Cellulose is a sustainable alternative to traditional plastic materials, with its natural abundance, high specific stiffness, and biodegradable properties. Cellulose biocompatibility and non-toxic nature make it a desirable choice for environmentally conscious businesses and consumers (Ren et al., 2022). Wang et al. (2017) have developed a micro/nano cellulose-PLA composite with up to 30 % of fiber content level; the mechanical properties of 3D printed parts reached a comparable level to that of pure PLA with elongation at break of 12 %, tensile strength of 57,7 MPa and flexural strength of 50,7 MPa. However, the intricate process involved in preparing cellulose, combined with its low proportion, limited properties enhancement, and high cost, restricted the application of PLA-Cellulose composites (Ambone et al., 2020; Murphy and Collins, 2018; Qu et al., 2012).

Many studies investigated the influence of wood fibers on 3D printing performances when added to PLA matrix, proving that wood-based materials not only reduce material costs of the pure matrix but also act as reinforcement of the resulting composites. Incorporating wood fiber results in materials exhibiting enhanced stiffness, toughness, strength, and thermal conductivity (Estakhrianhaghighi et al., 2020; Graichen et al., 2017). Depending on wood particle content, size distribution, aspect ratio, and compatibility with the matrix, this natural fiber acts either as a filler or a reinforcement (Kariz et al., 2018). Kariz et al. (2018) have used a wood powder fraction of 10 %-50 % with PLA pellets; the tensile strength increased from 55 MPa to 57 MPa at 10 % wood fiber, but at 50 % wood fiber decreased the tensile strength, mainly because the polymer struggled to fully encapsulate the wood particles causing poor bonding and load transfer. Liu et al. (2019) prepared composites using PLA matrix and different fibers (bleached pulp powder, newspaper pulp powder, pine powder, and lignin) for 3D printing; from the measurements, the tensile strength reached a maximum value at 15 % weight level. Wood fibers contribute to high rigidity, increase porosity and water absorption, and often reduce mechanical properties (Guo et al., 2018). Consequently, numerous studies have focused on enhancing the properties of wood-based filaments (Das et al., 2021). The combination of PLA and wood charge presents a major challenge; the hydrophilic nature of wood and the hydrophobicity of

PLA lead to poor interfacial bonding, resulting in a decrease in the strength properties of 3D parts (Le Guen et al., 2019). In addition, wood powder affects the thermal stability of 3D printed parts, decreasing the thermal decomposition and the glass transition caused by the poor compatibility between the matrix and the filler (Ecker et al., 2019).

Wood combustion is a prominent method of energy production and has been widely adopted for its renewable nature. However, this process generates significant amounts of waste in the form of wood ash, which poses environmental concerns due to the potential leaching of heavy materials into groundwater. The combustion of wood chips results in three ash fractions: great ash for 20–30 %, which is used as a fertilizer; cyclone ash (2–160 µm) for 30–60 %, and electro-filter precipitator ash (particle size smaller than 10 µm) for 5–15 % (Lazik et al., 2020). To achieve sustainable technologies, minimizing and exploiting industrial wastes as secondary raw material resources is important. Few studies have considered wood ashes as a reinforcement in the production of biocomposites (Sanusi et al., 2013; Singla and Chawla, 2010). Daramola et al. (2020) investigated the influence of bamboo stem ash on polyester matrix with up to 8 % reinforcement. These fillers reduced the porosity of the polyester, and 2 % of the content level gave the optimum tensile strength; however, the optimum flexural strength was reached at 29.5 MPa with 6 % of bamboo ash.

Several researchers have explored using particles to reinforce composites for improved properties (Badouard et al., 2019; Guessasma et al., 2019a). However, none of these studies specifically compared the properties of PLA composites with forest industrial residues such as wood ashes and wood sawdust or cellulose fiber up to 20 % content to produce 3D-printed biodegradable containers. The present study explores the potential of biocomposite filaments based on PLA with forest industrial residues, which provides a new type of green and biodegradable material. The main objective was to maximize the residue fillers amount in PLA up to 20 % of the weight fraction. More specifically, this study aims to investigate the effect of filler type and filler weight fraction on the biocomposites’ surface chemistry, thermal properties (DSC and TGA), mechanical performance (tensile, flexural, and impact), microstructure, water absorption, dimensional stability, and rheological behavior.

## 2. Materials and methods

### 2.1. *Samples preparation*

The multinational Natureworks LLC supplied the polylactic acid (PLA) pellets (Ingeo Biopolymer 4032D grade). The density of PLA was 1.24 g/cm³ with a molar mass $M_n$ of 165 g/mol and a melt flow index (MFI) of 5,89 g/10 min. The PLA was oven-dried at 80 °C for 8 h to eliminate moisture and minimize air bubbles or porosity in the resulting filaments. Rettenmaier Canada provided cellulose fibers (Arbocel FD 00) with an average length of 150 µm. West Fraser, a local wood panel manufacturing company, provided the wood ashes (WA), and the Jack pine’s sawdust (JP) was grounded and sieved to achieve a filler size lower than 150 µm. Fillers were oven-dried at 80 °C for 24 h to achieve less than 3 % humidity. The PLA and cellulose fibers (CF) were mixed based on weight according to the formulations shown in Table 1.

Biocomposite pellets were obtained by extrusion using a twin-screw extruder (Haake PolyLab OS Rheodrive 7, HAKKE, Germany) with a temperature profile at 180 °C, 185 °C and 190 °C, respectively, from the feeder zone to the die zone and a rotation speed of 50 rpm. Extruded filaments were pelletized using a thermos Scientific standard pelletizer and then oven-dried at 70 °C for 24 h. The biocomposite pellets were processed into a spooling mechanism using a 3devo Composer 450 desktop filament maker (Utrecht, Netherlands), which is a single screw extruder. The diameter of the obtained biocomposite filaments falls within the range of 1,75±0.1 mm; the temperatures were set at 170 °C for the metering zone, 185 °C and 180 °C, respectively, for the transitioning zone, and 175 °C for the feeding zone, with a rotation speed of
<table><caption>**Table 1**
PLA and fillers formulation.</caption><thead><tr><th rowspan="2">Designation</th><th rowspan="2">PLA</th><th colspan="3">Fillers</th></tr><tr><th>Jack Pine's sawdust</th><th>Wood ashes</th><th>Cellulose fibers</th></tr></thead><tbody><tr><td>PLA</td><td>100 %</td><td>-</td><td>-</td><td>-</td></tr><tr><td>PLA5JP</td><td>95 %</td><td>5 %</td><td>-</td><td>-</td></tr><tr><td>PLA10JP</td><td>90 %</td><td>10 %</td><td>-</td><td>-</td></tr><tr><td>PLA15JP</td><td>85 %</td><td>15 %</td><td>-</td><td>-</td></tr><tr><td>PLA20JP</td><td>80 %</td><td>20 %</td><td>-</td><td>-</td></tr><tr><td>PLA5WA</td><td>95 %</td><td>-</td><td>5 %</td><td>-</td></tr><tr><td>PLA10WA</td><td>90 %</td><td>-</td><td>10 %</td><td>-</td></tr><tr><td>PLA15WA</td><td>85 %</td><td>-</td><td>15 %</td><td>-</td></tr><tr><td>PLA20WA</td><td>80 %</td><td>-</td><td>20 %</td><td>-</td></tr><tr><td>PLA5CF</td><td>95 %</td><td>-</td><td>-</td><td>5 %</td></tr><tr><td>PLA10CF</td><td>90 %</td><td>-</td><td>-</td><td>10 %</td></tr><tr><td>PLA15CF</td><td>85 %</td><td>-</td><td>-</td><td>15 %</td></tr><tr><td>PLA20CF</td><td>80 %</td><td>-</td><td>-</td><td>20 %</td></tr></tbody></table>

4 rpm.

Filaments were fed into a CreatBot DX plus printer using the Fused Deposition Modeling (FDM) technique to produce test samples. Solid-Works software was used for creating the CAD (Computer-Aided Design) models of the different samples. In addition, simplify 3D software was utilized to slice the CAD model and set the printing parameters. During the printing process, the FDM unit has a nozzle diameter of 0,8 mm, the extrusion temperature and the bed temperature were maintained at 200 °C and 60 °C, respectively, with an infill speed of 30 mm/s, 100 % infill percentage, a layer thickness of 0,4 mm, and the raster angle was ±45°. An example of the printed samples is shown in supplementary material (Fig. S1a).

## 2.2. Characterization of the biocomposites

### 2.2.1. Surface chemistry

Fourier Transform Infrared Spectroscopy (FTIR) tests were conducted using a Shimadzu IR Tracer-100 apparatus and employed to examine the surface chemistry of the different fillers and biocomposites. FTIR allows the identification of the functional groups and structural or chemical modifications resulting from different treatments. This technique characterized the chemical composition by identifying characteristic peaks when samples are exposed to infrared radiation. The infrared absorption region used was 4000–400 cm⁻¹ at a resolution of 8 cm⁻¹, averaging 64 scans. LabSolutions software analyzed the obtained data using.

### 2.2.2. Thermal properties

The characterization of filament samples was performed with Differential Scanning Calorimetry (DSC) according to the ASTM D3417 standard. Small specimens weighing 10–15 mg were analyzed using an aluminum crucible in a Q20 device equipped with a cooling accessory (TA Instrument, Newcastle, TX, USA). The following cycle was repeated twice: The heating run from 10 °C to 250 °C at a rate of 10 °C/min, isothermal for 1 min to rest the thermal history, and then the cooling from 250 °C to 10 °C at a rate of 10 °C/min. The resulting scans determined the melting temperature (T<sub>m</sub>), the glass transition (T<sub>g</sub>), and crystallization temperature (T<sub>c</sub>). The crystallinity of the samples X<sub>c</sub> was calculated using Eq. (1) (Lim et al., 2008):

$$X_{c}\% = \frac{\Delta H_{m} - \Delta H_{cc}}{\Delta H_{m}^{\circ} \times (w_{PLA})} \times 100 \quad (1)$$

where, ΔH<sub>m</sub> is the total melting enthalpy, ΔH<sub>cc</sub> is the enthalpy of cold crystallization, ΔH<sub>m</sub> is the theoretical enthalpy of fusion for fully crystalline PLA (93 Jg<sup>-1</sup>) (Pilla et al., 2008), and w<sub>PLA</sub> is the mass fraction of PLA in the sample.

The thermal stability of neat PLA, fillers, and filler-PLA biocomposite filaments was performed through thermogravimetric analysis using a

Q50 device from TA Instrument and regulated by TA Analysis software. Approximately 10–20 mg samples were deposited into standard platinum crucibles and subjected to a heating program from 10 °C to 600 °C at a rate of 40 °C/min in a nitrogen atmosphere. Thermal weight loss (TG) and derivative mass loss (DTG) curves were generated from the results. This technique was employed to estimate the oxidation kinetics, thermal degradation, onset and end temperature of degradation, residual mass, and the temperature at which the mass loss is most significant.

### 2.2.3. Mechanical properties

The mechanical properties of the 3D-printed biocomposites were investigated using a Zwick Universal Testing Machine equipped with a 20 kN load cell (Z020, Zwick Roell Group, Germany). The Young's modulus (E), tensile strength at yield (σ<sub>m</sub>), and elongation at break (ε<sub>b</sub>) were determined at a crosshead speed of 2 mm/min at ambient temperature. The reported results represent the average of at least four measurements under ASTM D 638 using type 1 samples.

Three-point flexural tests were assessed using ASTM D 790 and conducted with the same Universal Testing Machine. These tests aim to measure the apparent flexural modulus (MOE<sub>f</sub>), flexural strength, and maximum (σ<sub>mf</sub>) flexural strain (ε<sub>bf</sub>). These test results were determined by five samples at a 2 mm/min crosshead speed.

The Izod impact strength of the biocomposites was conducted according to ASTM D256 norm employing a Basic Pendulum Impact tester (BPI-5.5, Zwick Roell Group, Germany) with a pendulum energy of 2.75 Joules and controlled with TestXpert software. The reported impact strength results represent an average of ten measurements.

### 2.2.4. Water absorption test (WA) and thickness swelling (TS)

The proportion of water absorption and thickness swelling of 3D-printed samples was tested according to the ASTM D570 standard. Samples were immersed in distilled water at approximately 20 °C for a minimum duration of 60 days (1000 h). The water absorption percentage and the thickness swelling were calculated using Eqs. (2) and (3), respectively. Three replicates were used.

$$WA(\%) = \frac{W_w - W_d}{W_d} \times 100 \quad (2)$$

Where W<sub>d</sub> is the weight of the sample before immersing, and W<sub>w</sub> is the weight after immersion.

$$TS(\%) = \frac{T_w - T_d}{T_d} \times 100 \quad (3)$$

Where T<sub>d</sub> and T<sub>w</sub> represent the thickness before and after immersing, respectively.

### 2.2.5. Rheological measurements

The rheological characteristics of the 3D-printed samples were assessed utilizing a rotational rheometer (MCR302, ANTON PARR, Austria) featuring a pair of parallel plates within a nitrogen atmosphere. The printed samples had a diameter of 25 mm and a thickness of 2.5 mm. The test involved a frequency sweep panning from 0.1 to 100 rad/s, with a maintained strain of 1 % and a temperature of 180 °C. This technique included measuring storage modulus and complex viscosities.

### 2.2.6. Scanning electron microscopy (SEM)

This technique was employed to investigate the morphology of filaments and cross-sections of tensile testing specimens using a scanning electron microscope (ThermoFisher, Quattro S, USA). Samples were affixed to the aluminum stub using conductive adhesive with an acceleration voltage of 15 kV to prevent charging issues. An example of the cross-sections of the printed samples is shown in the supplementary material (Fig. S1b).
# 3. Results and discussion

## 3.1. Surface chemistry

FTIR characterized the surface chemistry of fillers (WA, CF, and JP) and biocomposites. The obtained spectra were a convenient method to detect changes in the chemical compositions during various processes, such as formation/ disappearance and increase/decrease of various bands. The typical bands for PLA polymer were presented in Fig. 1. The absorption bands of low intensity in wavenumber region of 3000–3800 cm⁻¹ were assigned to the stretching vibrations of the hydroxyl groups (-OH) (Guo et al., 2018; Liu et al., 2019), the bonds at 2854 cm⁻¹, 2924 cm⁻¹, 2947 cm⁻¹ and 2993 cm⁻¹ were attributed to the alkane stretching vibration bond in the aliphatic group (-C-H), the peak at 1743 cm⁻¹ corresponded to carbonyl group stretching (C=O) (Wu et al., 2022), the bands in the range of 1442–1273 cm⁻¹ were generally attributed to (C-H) deformation, the region of 1000–1180 cm⁻¹ were assigned to anti-symmetric and symmetric stretching vibration of (C-O) bonds (C-O-C, C-OH) (Patti et al., 2023) and the peaks at 867 cm⁻¹ and 756 cm⁻¹ were assigned to the amorphous and crystalline phases of PLA (Patti et al., 2023, 2022).

The absorbance spectra of the three fillers exhibited a common peak characteristic of hydroxyl group (-O-H) at a range of 3334 cm⁻¹, representing the stretching vibration absorption of -OH. In JP filler, the peak at 1724 cm⁻¹ corresponded to the stretching vibration absorption of the (C=O) group in hemicelluloses; the peak at 1600 was due to the presence of lignin and assigned to the aromatic (C=C) stretching vibration (Liu et al., 2019). The peak at 1026 cm⁻¹ represented the symmetric stretching vibration absorption (C-O-C), and the range of wavenumbers at 2897 belonged to the asymmetric and symmetric vibration absorption of the (CH₂) group (Guo et al., 2018). For CF, the 2900 cm⁻¹ was attributed to aliphatic saturated (-C-H) and the absorbance peak at 1427 cm⁻¹ was attributed to the crystallinity band (Long et al., 2022). The peak at 1022 cm⁻¹, between 1000 cm⁻¹ and 1300 cm⁻¹, indicated the (C-O) bonds associated with alcohol ethers, esters, carboxylic acid, or anhydride groups (Iwatake et al., 2008). The combustion of fillers could be responsible for reducing and losing functional groups. WA presented two important peaks at 871 cm⁻¹ and 1408 cm⁻¹ that can be attributed to the presence of calcite (CaCO₃), the out-of-banding and asymmetric stretch, respectively (Rumman et al., 2023).

The FTIR spectra of 3D printed biocomposites were similar to the neat PLA, meaning that most functional groups originated from PLA (Guo et al., 2018), suggesting poor interaction between PLA chains and fillers. However, the relative intensity of these groups varied, indicating the variety in the weight fraction of PLA and the proportion of fillers in the biocomposite samples.

The hydroxyl band (O-H) of the PLA-JP and PLA-CF printed bio-composites is broad and shifted to slightly lower wavenumbers as the filler content increased due to the increased number of hydroxyl groups introduced by the fibers (Narhoğlu et al., 2021). In PLA-JP bio-composite, the aliphatic group (-C-H)'s absorbance peaks increased with the fillers' content and shifted to slightly lower wavenumbers. Wood fibers contain cellulose, hemicellulose, and lignin, which are rich in (-C-H) groups that present additional sites for interaction with PLA. In addition, adding wood fillers to PLA can induce structural change, such as increased crystallinity that can affect the vibrational frequencies of the (-C-H) bonds, leading to lower wavenumbers (Guo et al., 2018). A small peak appeared with the addition of more than 10 % weight fraction of JP at ~1647 cm⁻¹ due to the presence of (O-H) peak originated from the unresolved bending vibrations of hydroxyl groups associated with the absorbed water typically found in cellulose (Mofokeng et al., 2012).

## 3.2. Thermal properties

### 3.2.1. Thermogravimetric analysis (TGA)

Fig. 2 shows the TG and DTG curves of all studied formulations. Table 2 provides the corresponding onset temperature (T<sub>onst</sub>), the temperature at 5 % and 20 % weight loss (T<sub>5%</sub> and T<sub>20%</sub>%, respectively), the temperature of the maximum degradation rate (T<sub>max</sub>), and residual weight at 600 °C.

For both CF and JP fillers, an initial mass loss was observed in Fig. 2a between 20 °C and 100 °C, attributed to water mass loss (Khouaja et al., 2021). CF and JP began their decomposition at 222 °C and 215 °C respectively, and the maximum mass loss occurred between 260 °C and 400 °C with approximately 20 % residual mass. The lignin in JP began decomposition at the lowest temperature, then the hemicellulose and the cellulose, which explained that CF was more thermally stable than JP (Bouafif et al., 2009). WA is stable up to a temperature of 600 °C with a higher residual mass of 90 %, as expected, due to the pre-treatment of cellulose and other wood components. The neat PLA and PLA filament curves were not different. PLA filament indicated an onset temperature at 295 °C with a relatively low mass of 0,4 %. The peak observed at 380 °C indicates the typical decomposition of PLA by the release of cyclic oligomers, lactide molecules, CO, and CO₂ (Zou et al., 2009). This finding was supported by the thermogravimetry coupled to Fourier transform infrared spectroscopy (TGA-FTIR) analysis of the thermal decomposition products evolved during the degradation of PLA (Zou et al., 2009). Increasing filler content decreased the biocomposites' T<sub>onst</sub>, T<sub>max</sub>, T<sub>5%</sub>, and T<sub>20%</sub> (Daver et al., 2018). This result is explained by the lower thermal decomposition of fillers than that of PLA and by the in-compatibility and weak interfacial bonding between fillers and polymer. All the materials were thermally stable up to 217 °C, whereas above 500 °C, the samples degraded completely.

Adding cellulose fillers to PLA resulted in a decrease in the thermal decomposition temperature of the biocomposites. This decline can be attributed to PLA's increased chain activity due to cellulose (Zhang, Cai et al., 2020). However, CFs were more thermally stable than the bio-composites based on JP and WA. Biocomposites containing wood ash have the lowest thermal stability; the filaments containing WA started to degrade sooner than the other samples, which did not exceed 217 °C for PLA20WA. This lower thermal stability has affected the printing temperature range, making it more restricted. In addition, increasing filler content increased the residual mass in biocomposites mainly because the residual mass of fillers is higher than that of PLA. Compared to the neat PLA, the reduction of the onset temperature of degradation is still higher than the printing temperatures used in this study, which was fixed at 210 °C.

### 3.2.2. Differential scanning calorimetry (DSC)

Table 3 summary of the DSC analysis of PLA and biocomposite filaments, where two behaviors are observed. The first one presented the heating cycle, including the glass transition temperature (T<sub>g</sub>), cold crystallization temperature (T<sub>cc</sub>), melting temperature (T<sub>m</sub>), cold crystallization enthalpy (ΔH<sub>cc</sub>), fusion enthalpy (ΔH<sub>m</sub>), and crystallinity degree (χ<sub>c</sub>) and the second cycle presented the cooling cycle including crystallization temperature (T<sub>c</sub>) and crystallization enthalpy (ΔH<sub>c</sub>). Fig. 3 shows a significant reduction of T<sub>g</sub> of neat PLA compared to biocomposites from 68 °C to 66 °C for PLA-WA, 65.6 °C for PLA-JP, and 65 °C for PLA-CF with 5 % of fillers. The glass transition temperature could be influenced by molecular characteristics, composition, and compatibility of the biocomposite components (Chung et al., 2002). It is important to highlight that T<sub>g</sub> slightly decreased with increasing filler content due to weak interfacial adhesion and interaction and poor compatibility between the PLA and the fillers (Lee et al., 2008) or the presence of voids (Zhang, Cai et al., 2020). Also, this could indicate that biocomposites could crystallize earlier than the neat PLA (Petchwattana et al., 2019). The biocomposites reinforced by CF exhibited the lowest
<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /><figcaption>Fig. 1. Surface chemistry of fillers (WA, CF, and JP) and biocomposites: a) PLA-JP, b) PLA-WA, and c) PLA-CF.</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>Fig. 2. Thermogravimetric analysis of a) fillers, b) PLA-CF filaments, c) PLA-WA filaments, and d) PLA-JP filaments.</figcaption></figure>

<table><caption>**Table 2**

Thermogravimetric analysis measurements of filament specimens.</caption><thead><tr><th>Formulation</th><th>T<sub>onst</sub> (°C)</th><th>T<sub>50%</sub> (°C)</th><th>T<sub>20%</sub> (°C)</th><th>T<sub>max</sub> (°C)</th><th>Carbon residue (%)</th></tr></thead><tbody><tr><td>Jack Pine</td><td>215.1</td><td>265.5</td><td>315.5</td><td>358.9</td><td>21.1</td></tr><tr><td>Wood Ashes</td><td>0.0</td><td>400.6</td><td>0.0</td><td>448.9</td><td>88.9</td></tr><tr><td>Cellulose</td><td>222.4</td><td>285.4</td><td>330.8</td><td>363.7</td><td>18.7</td></tr><tr><td>Fiber</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>PLA- Pellets</td><td>299.5</td><td>335.0</td><td>356.1</td><td>380.1</td><td>0.2</td></tr><tr><td>PLA- FILAMENT</td><td>295.1</td><td>333.8</td><td>351.7</td><td>368.9</td><td>0.4</td></tr><tr><td>PLA5WA</td><td>236.4</td><td>268.4</td><td>295.6</td><td>341.6</td><td>4.7</td></tr><tr><td>PLA10WA</td><td>231.7</td><td>258.2</td><td>282.9</td><td>307.5</td><td>8.6</td></tr><tr><td>PLA15WA</td><td>220.4</td><td>246.1</td><td>264.9</td><td>284.3</td><td>13.8</td></tr><tr><td>PLA20WA</td><td>217.9</td><td>238.8</td><td>255.3</td><td>262.7</td><td>21.4</td></tr><tr><td>PLA5CF</td><td>293.2</td><td>328.3</td><td>348.2</td><td>370.7</td><td>1.4</td></tr><tr><td>PLA10CF</td><td>275.6</td><td>322.9</td><td>343.5</td><td>365.1</td><td>2.3</td></tr><tr><td>PLA15CF</td><td>267.2</td><td>314.8</td><td>335.3</td><td>357.2</td><td>3.5</td></tr><tr><td>PLA20CF</td><td>261.6</td><td>313.7</td><td>334.5</td><td>355.2</td><td>3.9</td></tr><tr><td>PLA5JP</td><td>275.6</td><td>327.1</td><td>348.7</td><td>370.0</td><td>2.8</td></tr><tr><td>PLA10JP</td><td>266.5</td><td>309.1</td><td>330.3</td><td>350.9</td><td>3.2</td></tr><tr><td>PLA15JP</td><td>267.4</td><td>304.3</td><td>323.8</td><td>346.1</td><td>4.6</td></tr><tr><td>PLA20JP</td><td>256.1</td><td>295.6</td><td>316.6</td><td>339.6</td><td>6.6</td></tr></tbody></table>

interfacial adhesion with the matrix.

Adding filler residues did not have an evident influence on the melting temperature T<sub>m</sub>, which took the value of 176 ± 1 °C similar results have been reported by Gauss and Pickering. (2023); Tao et al. (2017). T<sub>cc</sub> of neat PLA, which occurred at 131 °C, was shifted to a lower temperature at 111 °C–99 °C for biocomposite filaments when the filler content was increased.

With the cooling process, PLA showed no peak under such a low cooling speed and indicated a lower crystalline content of 2.69 % (Shi et al., 2015). The χ<sub>c</sub> value obtained confirmed that PLA was almost completely amorphous (Ortenzi et al., 2015). No crystallization peak was observed with WA biocomposites. However, adding CF and higher than 5 % of JP increased T<sub>c</sub> and ΔH<sub>c</sub> of PLA. This result could be

explained by the fact that fillers impeded the movement of PLA molecular chains, requiring higher temperatures for the molecules to get out of the shackles and to complete phase transition, such as to a viscous or high-elastic state (Sheng et al., 2019). Finally, The rise in crystallinity with increasing filler content confirmed that this filler is an effective nucleation agent, facilitating the crystallization of the PLA even at low fillers content (Zhang, Y. et al., 2018). It is noteworthy that CF showed better nucleating ability than WA and JP.

### 3.3. Mechanical properties

Fig. 4a and b show the tensile strength, Young's modulus, and strain at the break of the 3D printed samples with various filler contents. The highest tensile strength was observed for the neat PLA sample with a value (51.64±1.76), in line with the finding of Raza et al. (2023). The maximum tensile strengths of PLA-JP, PLA-CF, and PLA-WA were (44.43 ±1.14 at 15 %), (34.12±1.91 at 10 %) and (47.26±4.06 at 5 %), respectively. These values were lower than pure PLA by 14 %, 34 %, and 8.5 %, respectively.

The elastic modulus results did not show a clear variation trend with filler content. With PLA20JP and PLA15CF, the tensile modulus increased with filler content and was higher by 20.9 % and 4 % than PLA, respectively. At PLA15WA, the tensile modulus increased by 11.3 % compared to pure PLA. The evolution of Young's modulus with increasing filler content can be attributed to a dual effect: a decrease in chain mobility resulting from a higher stress concentration and the reinforcing fillers' inherent stiffness (Milosevic et al., 2017).

Fig. 4c shows the relationship between the tensile strain and the filler proportion. Increasing the filler amount of JP, CF, and WA up to 20 % caused a significant reduction in tensile strain to 41 %, 64 %, and 50 %, respectively. Adding hydrophilic filler to hydrophobic PLA led to a reduction in the tensile elongation at break, localized stress concentration that made them susceptible to premature failure, and a decrease in the polymeric matrix ductility conducted to make more fragile bio-composites that resistless deformation before rupture; this is in
<table><caption>**Table 3**
Differential scanning calorimetry measurements of filament specimens.</caption><thead><tr><th>Formulation</th><th>T<sub>g</sub>(°C)</th><th>T<sub>m</sub>(°C)</th><th>ΔH<sub>m</sub>(J/g)</th><th>T<sub>cc</sub>(°C)</th><th>ΔH<sub>cc</sub>(J/g)</th><th>T<sub>c</sub>(°C)</th><th>ΔH<sub>c</sub>(J/g)</th><th>χ<sub>c</sub>(%)</th></tr></thead><tbody><tr><td>PLA</td><td>68.22</td><td>175.52</td><td>22.67</td><td>131.16</td><td>20.15</td><td>-</td><td>-</td><td>2.69</td></tr><tr><td>PLA5WA</td><td>66.11</td><td>177.16</td><td>26.71</td><td>111.49</td><td>23.28</td><td>-</td><td>-</td><td>3.86</td></tr><tr><td>PLA10WA</td><td>65.86</td><td>176.97</td><td>26.99</td><td>111.39</td><td>21</td><td>-</td><td>-</td><td>7.11</td></tr><tr><td>PLA15WA</td><td>65.64</td><td>175.5</td><td>22.23</td><td>105.17</td><td>20.11</td><td>-</td><td>-</td><td>7.70</td></tr><tr><td>PLA20WA</td><td>65.17</td><td>175.64</td><td>25.12</td><td>104.94</td><td>19.85</td><td>-</td><td>-</td><td>7.53</td></tr><tr><td>PLA5JP</td><td>65.63</td><td>177.62</td><td>21.68</td><td>112.32</td><td>20.57</td><td>-</td><td>-</td><td>3.25</td></tr><tr><td>PLA10JP</td><td>64.89</td><td>176.54</td><td>24.45</td><td>110.86</td><td>20.08</td><td>91.51</td><td>2.06</td><td>5.19</td></tr><tr><td>PLA15JP</td><td>64.83</td><td>177.15</td><td>23.77</td><td>109.06</td><td>18.73</td><td>92.26</td><td>3.79</td><td>6.33</td></tr><tr><td>PLA20JP</td><td>64.33</td><td>176.19</td><td>22.07</td><td>106.4</td><td>16.08</td><td>92.94</td><td>4.73</td><td>7.99</td></tr><tr><td>PLA5CF</td><td>64.98</td><td>176.36</td><td>21.79</td><td>109.28</td><td>18.46</td><td>96.48</td><td>16.85</td><td>3.75</td></tr><tr><td>PLA10CF</td><td>64.33</td><td>176.84</td><td>21.45</td><td>108.89</td><td>16.69</td><td>98.52</td><td>20.18</td><td>5.64</td></tr><tr><td>PLA15CF</td><td>63.72</td><td>176.98</td><td>22.25</td><td>105.71</td><td>15.82</td><td>100.92</td><td>20.37</td><td>8.08</td></tr><tr><td>PLA20CF</td><td>61.15</td><td>175.41</td><td>23.65</td><td>99.7</td><td>12.79</td><td>101.35</td><td>20.69</td><td>14.51</td></tr></tbody></table>

<figure><img src="image_8.png" /><figcaption>**Fig. 3.** Differential scanning calorimetry of a) PLA-JP filaments, b) PLA-WA filaments and c) PLA-CF filaments.</figcaption></figure>

agreement with the work of Petchwattana et al. (2019).

Fig. 4d, e, and f present the relationship between the flexural strength, flexural modulus, flexural strain, and filler content. The flexural strength and modulus values showed different trends. The flexural strength and modulus decreased by approximately 49 % and 25 %, respectively, adding up to 10 % cellulose content compared to the values of 115.9 MPa and 4.5 GPa for neat PLA. The values then increased at 15–20 % of CF to reach the same flexural modulus value as pure PLA. In the PLA-WA biocomposites, there was a reduction in flexural strength to 15 % of content, with a slight increase at 20 % of WA. However, the flexural modulus of PLA5WA was 8 % higher than neat PLA. This value decreased for PLA10WA and PLA15WA, then increased again for PLA20WA. PLA-JP 3D printed samples illustrated a reduction in flexural strength with the addition of fillers. These findings align with prior research by Kariz et al., (2018). In PLA5JP and PLA20JP biocomposites, the flexural modulus was 2 % and 11 % higher than neat PLA, respectively. Fig. 4f shows that flexural strain decreased with adding filler amounts.

The Izod impact strength is primarily influenced by various factors, including morphology, molecular weight, particle dispersion, wetting, and crystallinity (Bajwa et al., 2021; Mimini et al., 2019). The impact strength of both PLA and 3D printed biocomposite specimens was illustrated in Fig. 4g. As shown, adding filler from 5 % to 20 % resulted in a reduction in impact strength than that for pure PLA. At 20 % content, the impact strength decreased by 42 %, 38 %, and 65 % for JP, CF, and WA, respectively. This decrease is expected and explains that adding wood and its residues renders biocomposites brittle. As mentioned earlier, these results can be attributed to PLA's weak crystallization

ability and low crystallinity as a semicrystalline polymer. This factor was likely responsible for the low-impact strength of PLA (Zhang, Lei, et al., 2020). These results agree with previous findings (Daver et al., 2018; Zhang, Q. et al., 2018).

Compared to neat PLA, biocomposites' consistently lower tensile strengths were primarily influenced by filler voids and pull-out at lower filler content (5 %-10 %) and by filler agglomeration at high filler contents (15 %-20 %). The mechanical properties of filaments reinforced with natural fillers are significantly affected by filler length, alignment, dispersion, and interfacial bonding (Milosevic et al., 2017). Lower mechanical properties in printed samples might also be due to intra-layer porosity that arises from printing, where low pressure between layers and heterogenous temperatures increase voids (Le Duigou et al., 2020). In addition, at higher loads, weak bonding and uneven filler distribution in the PLA matrix led to small voids and stress concentration due to poor interfacial compatibility between hydrophilic fillers and hydrophobic PLA matrix. Oven-drying the filament before the FDM process is among the solutions to reduce the samples' porosity of the sample during printing, to eliminate any residual moisture. The variation in the diameter of the produced biocomposite filament is another reason for these properties decrease, which caused less material in the printed specimens and insufficiently fused layers. These results indicated that incorporating forest industrial residue fillers in PLA polymer did not produce the expected reinforcement.

### 3.4. Scanning electron microscopy

The SEM analysis investigated the surface roughness of the
<figure><img src="image_9.png" /><figcaption>**Fig. 4.** Mechanical properties of 3D printed PLA and its biocomposites as a function of filler content: a) Tensile modulus, b) Tensile strength, and c) Tensile elongation at break, d) Flexural strength, e) Flexural modulus, and f) Strain, g) Impact energy.</figcaption></figure>

biocomposites filaments (Figs. 5–7). The surface fracture of pure PLA is smooth, indicating a brittle behavior consistent with previous studies (Liu et al., 2019; Petchwattana et al., 2019; Zhang, Q. et al., 2018).

Adding forest residues to the PLA makes the filaments' surface slightly uneven with discontinuity points. This roughness with assembled filler visible on the surface became more pronounced with increasing filler content level up to 20 %. PLA encapsulated the fillers in certain areas, but gaps are present in the PLA / filler interface due to poor interfacial adhesion and the different polarity between the non-polar surface of the hydrophobic PLA and the polar surface of the hydrophilic fillers in good agreement with previous findings (Fico et al., 2022; Petchwattana et al., 2019). Adding fillers caused a debonding of the filler and pull-out from the matrix. In addition, filler agglomeration indicates poor dispersion and non-uniform distribution (Tekinalp et al., 2019; Xiao et al., 2019). Other factors contributed to creating this porous structure that presented restricted connectivity. The insufficient

fusion of the polymer and filler mixture during the intermixing and filament extrusion resulted in poor mechanical properties (Tekinalp et al., 2019) and trapped bubbles inside the matrix (Guessasma et al., 2019a).

The heat reaction during wood combustion at elevated temperatures eliminated most functional groups, and no shifts in polymer peaks were observed with the integration of WA. Thus, all the functional groups in PLA-WA biocomposites originated from the polymer, and no chemical reaction occurred between WA and PLA (Zhang, Cai et al., 2020). The absence of polar functional groups in WA, particularly hydroxyl groups, indicates poor compatibility between WA filler and PLA (Zhang, Cai et al., 2020). PLA-WA filament illustrated irregular bubbles at the surface that increased with WA content, and the biocomposites were very breakable, with 15 % and 20 %, making the printing experience difficult.

Fig. 8 shows the morphology of the cross-sectional structure of FDM-

<figure><img src="image_10.png" /><figcaption>**Fig. 5.** SEM analysis of the pure PLA cross-section a) filament and b) printed sample.</figcaption></figure>
<figure><img src="image_11.png" /><figcaption>Fig. 6. SEM analysis of the cross-section of filament samples at 1 mm.</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>Fig. 7. SEM analysis of the cross-section of filament samples at 400 µm.</figcaption></figure>

printed specimens. These specimens showed higher porosity with irregular characteristics than the filaments and were larger than in-layer porosities (Guessasma et al., 2019a). These voids resulted from the layering process and can be attributed to the material discontinuities

induced by the FDM process (Guessasma et al., 2019b). The poor printing quality is attributed to the inadequate flow and the misalignments between adjacent filaments, consistent with previous studies (Milosevic et al., 2017). The interlayer thickness between two deposited
<figure><img src="image_13.png" /><figcaption>Fig. 8. SEM analysis of the cross-section of 3D printed samples.</figcaption></figure>

layers increased with filler content. PLA20FIBRE presented an indistinct boundary between layers due to its high viscosity and a predominant elastic fraction over a viscous fraction (Xiao et al., 2019).

The volume and number of voids on the fracture surface increased with filler content due to the filler pull-out from the matrix or their formation during the FDM process (Guo et al., 2018; Tekinalp et al., 2019). The filler pull-out indicates poor interfacial adhesion between the filler and PLA, leading to inadequate filler-polymer stress transfer and a subsequent reduction in the mechanical reinforcement efficiency of the filler in the 3D-printed parts in good agreement with previous studies (Stoof et al., 2017; Tanase-Opedal et al., 2019; Vinod et al., 2024). In addition, when the filler content increased from 5% to 20%, its dispersion deteriorated, as shown by the agglomeration phenomenon (Fig. 8), which led to various defects in the samples (Guo et al., 2023).

The first observation confirmed that CF was longer than JP, and the fillers were weakly attached to PLA, causing nozzle clogging, which explained the porosity created by the printing. The fracture surface exhibited a heterogeneous and rough surface with increasing filler pull-out, featuring signs of agglomerated fillers in the PLA. This behavior explains the lower tensile strength and ductility (Gauss and Pickering, 2023).

### 3.5. Rheological behavior of biocomposites

The rheological behavior of different biocomposites, PLA-JP, PLA-CF, PLA-WA, and pure PLA, was examined to investigate the effect of melt flow characteristics on the mechanical properties and the 3D printing challenges process. Fig. 9 shows the variation of complex viscosity ($\eta'$) and storage modulus ($G'$) with frequency.

Fig. 9a shows that the complex viscosity of PLA-JP and PLA-CF increased with increasing filler concentration. The integration of fillers tends to reduce fluidity, disrupt the usual polymer flow, and restrict the mobility of chain segments (Pardo et al., 2010). At a lower angular frequency (< 5rad/s), the flow behavior in all biocomposites displayed a Newtonian flow (Spiridon et al., 2016). The complex viscosity decreased with frequency, which exhibited shear thinning characteristics. The strong shear thinning behavior might be due to the tendency of rigid filler and polymer's chain to align in the flow direction, weakening the viscous resistance and indicating interaction inter particles in the melt phase (Spiridon et al., 2016; Xiao et al., 2019).

The energy of storage at the interphase between the matrix and the filler could indicate the biocomposites' elastic behavior. An increase in storage modulus $G'$ in Fig. 9b was observed with increasing filler level with the whole frequency range. Due to the intrinsic rigidity of lignocellulosic fillers, the biocomposites' storage moduli were higher than the pure PLA at a lower angular frequency (< 5rad/s). This behavior is due to restricted filler deformation and weak interfacial adhesion, making the PLA's chain mobility difficult (Spiridon et al., 2016). Then, the slope of the curves decreased with increasing frequency (Pardo et al., 2010). The dispersion of CF and wood sawdust within the composite is non-uniform. Consequently, the $G'$ values might be attributed to the relaxation of the large, dispersed domains of the minor phase. The storage modulus increased with a higher frequency (Koo et al., 2020). Compared to pure PLA, the reduced magnitude of $G'$ curves of the PLA-CF and PLA-JP biocomposites indicated that the incorporation of fillers into the PLA matrix did not show a reinforcing effect (Spiridon et al., 2016). The influence of the filler decreased, and the matrix contribution became dominant. Higher viscosity over the frequency range of PLA-CF and PLA-JP indicated that these wood-based composites' fluidity and processability were more difficult than neat PLA, indicating hard printability and rough surface within the biocomposites caused by melt instability.

Unexpectedly, the viscosity and the storage modulus of PLA-WA progressively decreased with the addition of WA as the filler amount increased in the biocomposites. Specifically at low frequencies
<figure><img src="image_14.png" /></figure>

<figure><img src="image_15.png" /><figcaption>Fig. 9. Rheological behavior of 3D printed biocomposites, a) Complex viscosity (η') and b) Storage modulus (G').</figcaption></figure>

(< 1rad/s), the flow curves of all PLA-WA and the matrix exhibited a similar trend, indicating that in this range, the storage modulus behavior is influenced by the matrix (Scaffaro et al., 2018). Then, the PLA-WA storage modulus over this frequency was lower than the pure PLA. The decrease in the complex viscosity of PLA-WA in the hole frequency range compared to the matrix could be because WA filler might have accelerated the degradation of the PLA chain (Scaffaro et al., 2018).

## 3.6. Water absorption and thickness swelling

The water absorption test was very important to understand the composites' behavior while exposing them to environmental conditions to define their end-use applications. The test of thickness swelling, and water absorption tests were performed to investigate the impact of water molecules on the biocomposites' dimensional stability. Fig. 10 a and b illustrate the variation of the water absorption (WA) and the thickness swelling (TS) after two months of water immersion of PLA and the 3D printed biocomposites. Graphs showed three stages; the initial stage showed a rapid increase in (WA) and (TS) within the first day. After that, the water-soaking process exhibited a slower increase over the next seven days. Finally, absorption reached saturation with no further change with significant variation among the different formulations (Supian et al., 2021).

Hydrophobic PLA showed the highest dimensional stability with only 2% water absorption. However, at 20% filler content, the PLA-JP 3D-printed biocomposites recorded the highest water absorption and thickness swelling values than the other biocomposites, with 8% and 3.8%, respectively. The PLA20CF indicated 6.5% and 2.7% of water absorption and thickness swelling, respectively. The major challenge in using lignocellulosic filler in the composite is its susceptibility to moisture. This behavior was expected due to the presence of hydroxyl groups on the filler and wood sawdust surfaces and the associated hydrogen bonds of the water molecule. Increasing filler content increases OH

groups which results in more water absorption and thickness swelling (Awad et al., 2023; Petchwattana et al., 2019). Based on the FTIR results, the hydroxyl groups were higher in PLA-JP than in PLA-CF. Another factor that influenced (WA) and (TS) values was the presence of hemicellulose. Thus, JP's hemicellulose content was higher than CF fillers, making JP more hydrophilic (Ayadi et al., 2020; Supian et al., 2021). In addition, the poor compatibility between filler and PLA matrix caused the creation of voids and micro gaps, which served as sites for water or moisture (Supian et al., 2021). An increase in filler content led to an increase in the porosity of the composite resulting in higher water absorption (Raza et al., 2023). Further, the inadequate bonding between the layers led to the production of pores, generating water sites.

At 20% filler content, the PLA-WA biocomposites showed a slight water absorption and thickness swelling of 3.4% and 1.1%, respectively (Fig. 10a) caused by the disappearance of OH groups by combustion. The water uptake was mainly due to voids and weak interfacial adhesion. Still, the hydrophobic nature of wood ashes prevented water absorption (Ayadi et al., 2020).

## 4. Conclusions

In this study, biodegradable biocomposites made of PLA and IFR fillers were successfully produced using FDM technology. Samples containing up to 20% of JP, WA, and CF were generated and tested. FTIR measurements suggested poor interaction between PLA chains and fillers. TGA results revealed a decrease in the thermal stability with incorporating fillers. While PLA-CF biocomposites exhibited the highest thermal stability, PLA-WA had the lowest. DSC analysis indicated reduced glass transition temperature and enhanced crystallinity with increasing the filler loading. Crystallinity was enhanced and reached 14.51% with PLA20CF compared to 2.69% for pure PLA. Mechanical measurements noted that incorporating fillers increased brittleness and reduced strength, strain, and impact energy. SEM results indicated an
<figure><img src="image_16.png" /><figcaption>Fig. 10. a) Thickness swelling, b) Water absorption and of 3D printed biocomposites.</figcaption></figure>

increase in filler content led to a heterogeneous surface with increasing porosity, roughness, and visible clusters for both filament and printed parts. Water absorption and dimensional accuracy of biocomposite increased with adding fillers. PLA-JP biocomposite showed the highest water absorption level. Furthermore, the rheological investigations confirmed that the complex viscosity and storage modulus of PLA-JP and PLA-CF increased with filler. However, PLA-WA showed the opposite trend. Although their mechanical properties are limited, these bio-composites' biodegradability and biobased characteristics make them suitable for biodegradable container applications in harmony with the aims of the circular economy. Future research should focus on improving their compatibility and mechanical properties through adhesive agents.

CRediT authorship contribution statement

**Sofiane Guessasma:** Writing – review & editing, Validation, Resources, Project administration, Investigation, Funding acquisition, Formal analysis, Conceptualization.
**Martin Beauregard:** Writing – review & editing, Validation, Supervision, Resources, Project administration, Investigation, Funding acquisition, Conceptualization.
**Hedi Nouri:** Writing – review & editing, Validation, Supervision, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization.
**Ahmed Kou-baa:** Writing – review & editing, Validation, Supervision, Resources, Project administration, Investigation, Funding acquisition, Conceptualization.
**Sarra Helaoui:** Writing – original draft, Visualization, Software, Methodology, Investigation, Formal analysis, Data curation.
## Funding

The Authors acknowledge the financial contribution of the Canada Research Chair Program (Grant: 694272); Mitacs (Grants: IT20598 and IT36806); CRSNG-CRSH (Grant: NFRFE-2018-00885); Fonds de Recherche du Québec Audace (Grant: 273167).

## Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Appendix A. Supporting information

Supplementary data associated with this article can be found in the online version at doi:10.1016/j.indcrop.2024.119799.

## Data availability

Data will be made available on request.

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