PLA Biocomposites Research Articles

Environmentally friendly approaches for tailoring interfacial adhesion and mechanical performance of biocomposites based on poly(lactic acid)/rice straw.

In the present research, plant-based biocomposites containing poly(lactic acid) (PLA) and rice straw (RS) as an annually renewable agricultural waste were studied. To enhance the properties of these filled systems, two environmentally friendly pulping methods were applied to remove the non-cellulosic components of RS and fibrillate the fibers. In addition, two reactive compatibilizers based on functional epoxy and maleic anhydride groups were incorporated into the biocomposites, using a reactive extrusion process. By pulping the RS fibers and modifying the PLA/lignocellulosic filler interface, the plant-based biocomposites with enhanced performance were attained. Furthermore, the elastic modulus, tensile strength, tensile toughness, impact strength, hardness, density and Vicat softening point of PLA and filled PLA system with untreated RS were improved. The impact resistance, tensile strength and elastic modulus of neat PLA were enhanced by 40 %, 160 % and 100 % for the modified biocomposites containing the environmentally friendly RS pulps. The obtained results showed that, these biocomposites had even higher mechanical performance than the PLA biocomposites containing RS pulp obtained through common soda-pulping method. The reasons behind these improvements are the partial pulping of RS, as well as the chain extension of PLA macromolecules and PLA grafting onto the lignocellulosic fiber surfaces induced by the reactive compatibilizers.

The Influence of In-Mould Annealing and Accelerated Ageing on the Properties of Impact-Modified Poly(Lactic Acid)/Biochar Composites

In the last few decades, a large number of natural additives have been analysed in connection with the improvement of the properties of poly(lactic acid) (PLA) bioplastic materials. This article comprehensively analyses the applicability of a highly stable and progressive multifunctional additive produced from renewable resources—biochar. The effect of biochar on the structural development and various thermo-mechanical properties was evaluated as a function of the biochar size and volume, addition of an impact modifier and in-mould annealing during injection moulding. In addition, the effect of accelerated ageing on the change in properties was also analysed. The evaluated results showed a significant influence of the particle size and biochar content on the properties of PLA biocomposites. However, the crucial aspect was the production process with a higher mould temperature and longer production time. Consequently, the effect of additives with adjusted processing worked synergistically on the performance of the resulting biocomposites. The accelerated ageing process did not induce any significant changes in the mechanical, impact and heat resistance behaviour of neat PLA. On the other hand, significant effects on the behaviour of the modified PLA biocomposites were observed. Impact-modified PLA achieved a toughness of 28 kJ/m2, an increase of 61% compared to neat PLA. Similar observations were made when submicron biochar was incorporated into the PLA matrix (a 22% increase with PLA/5B1). These increases were even more pronounced when injected into a 100 °C mould. Due to the synergistic effect, excellent impact toughness results of 95 kJ/m2 (a 428% increase) were achieved with PLA/IM/5B1. Moreover, these results persisted even after accelerated ageing.

Study of Mechanical and Thermal Properties of Environmentally Friendly Composites from Beer Bagasse.

The influence of bagasse fibres from beer manufacturing in mechanical, thermal, and rheological properties of three polymers (BioPE, PLA, and PP) has been studied in order to develop new environmentally friendly biocomposites for injection moulding applications. Totals of 10 wt%, 20 wt%, and 30 wt% of bagasse fibre (BSG) were added to the polymers by extrusion compounding, adding specific compatibilising additives, and injected samples were mechanically characterised by tensile, Charpy impact, and hardness tests. In addition, the fractures obtained after the impact test were observed using scanning electron microscopy (SEM) to assess the compatibility matrix filler. Characterisation of the thermal properties is also carried out by using differential scanning calorimetry (DSC) and thermogravimetry (TGA). Additionally, melt flow index of the biocomposites is also studied. An increase in the rigidity of the BioPE and PP composites was produced with the increase in BSG content, dealing with a decrease in maximum strain and impact resistance; whereas, in the filled BGS PLA biocomposites, Young's modulus was lower than that of the PLA material, improving the ductility of the PLA-BGS formulations. Compatibilisation effect was, therefore, different in the nine developed formulations, and the BGS content also influenced their thermal, mechanical, and rheological behaviours.

Sustainable strategy for lignin etherification and its promotion of anti-UV aging PLA biocomposite

Achieving efficient modification of both phenolic (Phe)-OH and aliphatic (Aliph)-OH groups in lignin simultaneously via sustainable method, remained a significant challenge. In this study, a series of highly hydroxyl-substituted alkali lignin phenyl propylene ketone ethers (ALK) were obtained under 50 °C without any by-products via the mild and sustainable hydroxyl-yne click reaction method. Notably, phenolic (Phe)-OH content of lignin decreased from 4.12 mmol g−1 to 0.07 mmol g−1 with a conversion rate of 98 %, while the aliphatic (Aliph)-OH content of lignin decreased from 2.57 mmol g−1 to 0.10 mmol g−1 with a conversion rate of 96 %. Owing to the efficient etherification, ALK showed excellent organic solvent (such as trichloromethane, DCM, THF, and acetone) solubility, which thereby improving the interfacial compatibility between ALK and PLA matrix. 3 wt% ALK obviously enhanced the mechanical properties of ALK/PLA biocomposite films, with the yield strength, breaking strength, and Young’s modulus improving by 114.2 %, 30.7 % and 250.2 %, respectively. Additionally, due to the newly introduced vinyl ether bonds (−C–O–CC–) in ALK by hydroxyl-yne click reaction, only 1 % ALK could endow ALK/PLA biocomposite with excellent UV shielding (100 %), high transmittance (84.3 %) and Anti-UV aging property. The yield strength and Young’s modulus represented an increase of 209 % and 86 %, respectively, even after 3 h of UV-irradiation. This study presents an environmentally friendly lignin functionalization method that unleashes the inherent Anti-UV aging properties of lignin, opening new avenues for the development of high-performance lignin-based composites.

Physio-mechanical and thermal characteristics of Mimosa pudica microfibers impregnated novel PLA biocomposite

Physio-mechanical and thermal characteristics of Mimosa pudica microfibers impregnated novel PLA biocomposite

Effect of unbleached and bleached softwood cellulose pulp fibers on poly(lactic acid) properties

Global regulations are guiding society towards more sustainable material solutions. This increasing awareness of the need for environmentally friendly alternatives has led to a greater emphasis on biocomposites, which combine natural fibers with bio-based polymers. This study investigates how bleached softwood pulp fibers (BSWPF) and unbleached softwood pulp fibers (UBSWPF) affect the characteristics of poly(lactic acid) (PLA)-based biocomposites. UBSWPF is a more cost-effective option because it is manufactured with less processing steps than BSWPF. However, it is largely unexplored as a reinforcement in biopolymers. Through investigating the mechanical, thermal, and morphological aspects of the biocomposites, this study showed that UBSWP increased the modulus and impact strength of the PLA biocomposites better than BSWPF. The impact strength, modulus, and tensile strength of PLA-BSWPF and PLA-UBSWPF improved as the fiber content increased. However, a decrease in tensile strength was seen at higher percentages of UBSWPF in PLA. Despite the decrease in tensile strength at higher UBSWPF concentrations, both types of fibers improved the mechanical properties of the biocomposites, demonstrating a potential sustainable reinforcing material for PLA biocomposites.

Moisture effect on tensile and low‐velocity impact tests of flax fabric‐reinforced PLA biocomposite

AbstractThis study investigates the hygrothermal aging effect on the tensile and impact behavior of flax/PLA biocomposites. Specimens underwent up to four weeks of conditioning at 40°C in a climate chamber with water. Analysis covered porosity, moisture diffusibility, and transversal microstructure, enabling assessment of tensile strength, tensile modulus, and impact performance in relation to moisture uptake and fiber orientation. The study of tensile properties revealed that at approximately 12% moisture content, stiffness and yield stress decrease, while strength remains constant. Moisture diffusivity is higher in warp and weft yarn directions than the out‐of‐plane direction. Tensile testing at environmental equilibrium moisture reveals greater stiffness in the weft direction, correlated with lower crimp percentage and yarn angle. The main contribution of the paper is the study of the influence of moisture on the impact behavior, the results show that energy absorption capability of flax/PLA biocomposite increases with moisture content.Highlights Fully biodegradable composite material by heat‐compression molding subjected to hygrothermal aging conditions for up to four weeks. The moisture diffusivity in both the warp and weft yarn directions registered higher values in comparison to the out‐of‐plane direction. Tensile testing at environmental equilibrium moisture revealed that the stiffness in the weft direction presented higher values. At 12% of moisture uptake, the stiffness and yield stress reached their lowest values, while strength remained constant. However, the low‐velocity impact properties of the composites exhibited improvement with moisture.

Static and dynamic mechanical characterization and thermal analysis for multi‐ply structure of woven nettle (Girardinia diversifolia) reinforced poly(lactic acid) biocomposites

AbstractPoly(lactic acid) fiberwebs and multi‐ply assemblies of nettle woven reinforcement are used to develop a series of nettle/PLA biocomposites with different reinforcement orientations. The tensile strength, flexural strength, impact strength, and thermal properties of the biocomposites are found to improve by piling nettle fabrics and are also found to depend strongly on the piling architecture and the test direction. It is possible to obtain a biocomposite with higher degrees of isotropy and enhanced mechanical properties by using cross‐ply laminates. The three‐layered woven fabric reinforced PLA biocomposite with a reinforcement orientation 0°/45°/90° shows the best results among all the biocomposites developed in this study. The tensile strength, Young's (tensile) modulus, flexural strength, impact strength, storage modulus, and loss modulus of the biocomposite are found as 55.25 MPa, 6.30 GPa, 85.83 MPa, 63.74 J/m2, 10.08 GPa, and 0.75 GPa, respectively. In this biocomposite, a fair adhesion between matrix and reinforcement is noticed, and this is justified by retardation of crack propagation as well as by substantial energy dissipation. The thermal stability of the biocomposite does not get effected much, but the percent crystallinity increases by 25.84%. The degradation kinetics and the activation energy of the biocomposite are determined through a differential fitting of Arrhenius model. The soil burial test reveals 15.06% of weight loss and 50.56% strength loss for this biocomposite just after 20 days of burial under soil.Highlights Multi‐ply architecture of woven fabric reinforcement in nettle/PLA biocomposites. Nearly isotropic biocomposite through angle‐ply orientation of reinforcement. Biocomposite with remarkable static and dynamic mechanical properties. Augmented kinetic parameters through model fitting of Arrhenius equation. Biocomposite with excellent thermo‐recyclability and biodegradability.

Biodegradability and Water Absorption of Macadamia Nutshell Powder-Reinforced Poly(lactic Acid) Biocomposites

This study investigates the biodegradability and water absorption properties of Macadamia nutshell powder and poly(lactic acid) (PLA) biocomposites using a Design of Experiments (DOE) approach. The influences of processing methods, the Macadamia nutshell powder’s weight content, and the powder’s condition are studied. A biodegradability test is performed in accordance with the American Society for Testing and Materials (ASTM) D5338-11 by burying the test specimens in wet garden soil at a controlled temperature of 50 °C and 100% humidity. The specimens obtained by counter-rotating processing exhibit varying weight loss patterns with an increasing powder weight content, while the specimens obtained by co-rotating processing demonstrate consistent behaviour. This study highlights the complex nature of PLA biodegradation, which is affected by diverse factors such as test conditions and environments, thereby contributing to a deeper understanding of the sustainability implications. A water absorption test is carried out in accordance with ASTM D570-98. It is shown that the water absorption characteristics are predominantly determined by the hydrophilic nature of Macadamia nutshells, with an increased powder weight content leading to higher absorption. Pure PLA, due to its hydrophobic nature, exhibits minimal water absorption. By unravelling the complexities of PLA biodegradation and water absorption in Macadamia nutshell and PLA biocomposites, this study not only advances the understanding of materials’ behaviour but also underscores the potential sustainability implications of utilizing natural resources in composite materials. This research contributes valuable insights to the broader discourse on environmentally friendly materials and their role in promoting sustainable practices.

Critical role of the composition of the cell culture medium on cell attachment and viability on PLA biocomposite scaffolds under in vitro assay conditions

In tissue engineering applications 3D scaffolds undertake the function of the native extracellular matrix (ECM) for cell attachment, survival, proliferation, and differentiation. For successful long-term implementation scaffolds need to mimic the ECM in vitro and in vivo. Many studies have focused on protein adsorption as the most critical factor for cell attachment. To improve protein adsorption on polymeric scaffolds various physical and chemical surface modification techniques, such as changing surface porosity, surface energy, and introducing various functional surface chemical groups have been investigated. It is well studied and documented that complex interactions between the biomaterial surface and the cell culture components in in vitro assay conditions define the scaffold performance. In this study influence of in vitro assay components on HepG2 liver cell attachment and proliferation on 3D printed poly(lactic acid) (PLA) scaffolds coated with various polymeric electrospun webs were investigated. MTT assays were performed on the scaffolds by using 3 different cell culture media; (i) basal cell culture medium (DMEM), (ii) DMEM supplemented with 10% albumin, and (iii) DMEM supplemented with 10% fetal bovine serum (FBS). Results obtained have shown dramatic improvement in cell attachment and proliferation in DMEM supplemented with 10% FBS when compared with DMEM and DMEM containing 10% albumin. Our findings clearly demonstrate synergistic effects of all bioactive components present in the FBS medium in significantly improving the HepG2 cell attachment and proliferation on polymeric scaffolds under in vitro conditions, regardless of the substrate structure, composition, and surface properties.

Multi-Attribute Decision Making: Parametric Optimization and Modeling of the FDM Manufacturing Process Using PLA/Wood Biocomposites.

The low carbon footprint, biodegradability, interesting mechanical properties, and relatively low price are considered some of the reasons for the increased interest in polylactic acid-based (PLA-based) filaments supplied with natural fillers. However, it is essential to recognize that incorporating natural fillers into virgin PLA significantly impacts the printability of the resulting blends. The complex inter-relationship between process, structure, and properties in the context of fused deposition modeling (FDM)-manufactured biocomposites is still not fully understood, which thus often results in decreased reliability of this technology in the context of biocomposites, decreased accuracy, and the increased presence of defects in the manufactured biocomposite samples. In light of these considerations, this study aims to identify the optimal processing parameters for the FDM manufacturing process involving wood-filled PLA biocomposites. This study presents an optimization approach consisting of Grey Relational Analysis in conjunction with the Taguchi orthogonal array. The optimization process has identified the combination of a scanning speed of 70 mm/s, a layer height of 0.1 mm, and a printing temperature of 220 °C as the most optimal, resulting in the highly satisfactory combination of good dimensional accuracy (Dx = 20.115 mm, Dy = 20.556 mm, and Dz = 20.220 mm) and low presence of voids (1.673%). The experimentally determined Grey Relational Grade of the specimen manufactured with the optimized set of process parameters (0.782) was in good agreement with the predicted value (0. 754), substantiating the validity of the optimization process. Additionally, the research compared the efficacy of optimization between the integrated multiparametric method and the conventional monoparametric strategy. The multiparametric method, which combines Grey Relational Analysis with the Taguchi orthogonal array, exhibited superior performance. Although the monoparametric optimization strategy yielded specimens with favorable values for the targeted properties, the analysis of the remaining characteristics uncovered unsatisfactory results. This highlights the potential drawbacks of relying on a singular optimization approach.

Utilizing the Potential of Waste Hemp Reinforcement: Investigating Mechanical and Thermal Properties of Polypropylene and Polylactic Acid Biocomposites.

Hemp has gained significant popularity for its diverse applications; however, this study explores the untapped potential of waste hemp (wH) as a cost-effective and sustainable bioadditive for the development of high-performance biocomposites. wH offers advantages such as low cost, easy availability, and suitability for extrusion. Polypropylene (PP) and poly(lactic acid) (PLA) served as polymer matrices for this investigation. In order to enhance the interaction between the wH and polymer matrices, alkaline and silane pretreatments were applied to the wHs of both matrices. At the same time, the MA-g-PP additive was used exclusively for the PP matrix. The resulting PP biocomposite demonstrated Young's modulus (2986 MPa) and flexural modulus (2490 MPa), surpassing those of neat PP by 109 and 77%, respectively. Similarly, wH40-PLA-A showed enhancements in the PLA biocomposite, with Young's modulus (6214 MPa) and flexural modulus (5970 MPa) representing an increase of 81 and 56% over that of neat PLA, respectively. The thermal properties and behaviors of the resulting biocomposites were minimally affected by the inclusion of wH as a bioadditive. This study contributes to the advancement of sustainable materials and provides valuable insights into the utilization of wH as a valuable resource for the development of high-performance biocomposites.

Polylactic Acid Polymer Matrix (Pla) Biocomposites with Plant Fibers for Manufacturing 3D Printing Filaments: A Review

The escalating global demand for polymer products and the consequent disposal challenge necessitate technological and sustainable solutions. Recent advances in the development of materials used in 3D printing equipment are described in this review, with a focus on new biocomposite materials. The investigation delves into biocomposites comprising PLA and its blends with other polymers, reinforced by plant fibers, with a particular focus on research conducted over the last five years. The information related to the raw materials’ physical, chemical, and processing properties necessary for creating biocomposite filament and printed parts were summarized. The best results in terms of tensile and flexural strength were presented and discussed, signposting future research avenues and desirable objectives. The findings elucidate that the inclusion of plant fibers led to a reduction in mechanical strength relative to pure PLA; however, when smaller particle sizes of plant fibers were added in volumes below 10%, it resulted in improved performance. Moreover, physical and/or chemical pretreatment of fibers, along with the isolation of cellulose fibrils, emerged as pivotal strategies for bolstering mechanical strengths. Noteworthy are the promising prospects presented by the incorporation of additives, while the refinement of printing parameters is key to improving the tensile and flexural strength of printed components.

Life cycle assessment of agave bagasse management strategies: PLA biocomposites versus conventional waste disposal practices

Tequila production is one of Mexico's largest agro-industries, generating significant amounts of agave bagasse (AB) as its primary solid waste. Current AB management practices encompass composting, open dumps, and incineration. Life cycle analysis was developed to compare the environmental impact of these management scenarios with developing value-added agave fiber (AF) reinforced plastic biocomposites and generating biogas through anaerobic digestion. The assessment compares three molding methods for the PLA-AF biocomposite, with the environmental impact evaluated against pure PLA and low-density polyethylene (LDPE). Extrusion-injection molding was the most environmentally friendly molding method across all indicators, primarily due to the reduced inputs required for pretreating the fibers. Among the current management scenarios, composting was the least environmentally impactful for the global warming potential indicator. Nonetheless, composting requires substantial time and land use, posing challenges for some producers. Incineration displayed a significant trade-off on the fossil resource scarcity indicator by replacing natural gas. Anaerobic digestion displayed high impacts in all indicators as AB does not yield high methane potential. While the production of PLA-AF displays a significantly higher environmental impact, it remains a preferable option when compared to pure PLA and may further improve its sustainability through green chemistry principles. Notably, LDPE was less environmentally impactful than both bioplastic options assessed, due to the environmental impacts of PLA production and the widespread standardization of LDPE production processes. Context-specificity is critical to assess the environmental impact of circular bioeconomy pathways, which are not always inherently beneficial, while addressing SDG 12: Responsible Consumption and Production.

The Evolution of the Intrinsic Flexural Strength of Jute Strands after a Progressive Delignification Process and Their Contribution to the Flexural Strength of PLA-Based Biocomposites.

Biocomposites from poly-(lactic acid) (PLA) and jute strands were prepared, and their flexural strength was analyzed. Jute strands were submitted to a progressive delignification process and the resulting morphology, composition, and crystallinity index were evaluated. Then, PLA biocomposites comprising 30 wt% of jute strands were produced and characterized under flexural conditions. The delignification processes decreased the lignin content and progressively increased the cellulose content. All this resulted in an enhancement of the composite flexural strength. A modified rule of mixtures, and the relation between tensile and flexural properties were used to determine the intrinsic flexural strength (of the jute strands) and their correlation with their physic-chemical characteristics. Equations correlating the intrinsic flexural strength with the crystallinity index, the cellulose content, and the microfibril angle were proposed. These equations show the impact of these properties over the intrinsic properties of the fibers and can help researchers to select appropriate fibers to obtain accurate properties for the composites. Jute strands show their value as reinforcement by increasing the flexural strength of the matrix by 70% and being less expensive and more environmentally friendly than mineral reinforcements. Together with the profitability and the environmental advantages, the mechanical results suggest that these PLA biocomposites are suitable for specific products of different market sectors.

Accelerating the Biodegradation of Poly(lactic acid) through the Inclusion of Plant Fibers: A Review of Recent Advances.

As the global demand for plastics continues to grow, plastic waste is accumulating at an alarming rate with negative effects on the natural environment. The industrially compostable biopolymer poly(lactic acid) (PLA) is therefore being adopted for use in many applications, but the degradation of this material is slow under many end-of-life conditions. This Perspective explores the feasibility of accelerating the degradation of PLA through the formation of PLA-plant fiber composites. Topics include: (a) key properties of PLA, plant-based fibers, and biocomposites; (b) mechanisms of both hydrolytic degradation and biodegradation of PLA-fiber composites; (c) end-of-life degradation of PLA and PLA-plant fiber composites in aerobic and anaerobic conditions, relevant to compost, soil and seawater (aerobic), and landfills (anaerobic); and (d) sustainability and environmental impact of PLA and PLA-plant fiber composites, as evaluated using life cycle assessment. Additional degradation modes, including thermal and photodegradation, which are relevant during processing and use, have been omitted for clarity, as have other types of PLA biocomposites. Multiple studies have shown that the addition of some types of plant fibers to PLA (to form PLA biocomposites) accelerates both water transport in the material and hydrolysis, presenting a possible avenue for improving the end-of-life degradation of these materials. To facilitate the continued development of materials with enhanced biodegradability, we identify a need to implement testing protocols that can distinguish between different degradation mechanisms.

Design and Development of highly filled calcium sulfate-poly lactic acid biocomposites as feedstock for low-cost fused filament fabrication

Three-dimensional (3D) printing has been used as a promising technology in biomedical sciences and engineering. However, there is a lack of ready-to-use feedstock for biomedical applications. In this work, a series of PLA biocomposite filled with calcium sulfate (CaS) particles up to a maximum content of 40 wt% has been prepared by solvent casting method and subsequently processed into filament form through the melt compounding method. The objective of this study was to investigate the processibility of composite filament with maximum ceramic content through fused filament fabrication (FFF) process to improve the mechanical, thermal and biological performance of virgin PLA for biomedical application. The composite filament was extruded at a temperature of 160 °C at a constant speed with an average diameter of 1.70 ± 08 mm, compatible with the 3D printer's feeding system. Morphological, thermal, mechanical, and crystallization analysis using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric (TGA) analysis was performed on the extruded filament to evaluate the effect of ceramic content in the polymeric matrix. The thermal stability was improved upon addition of CaS particles into the PLA matrix. Subsequently, PLA-CaS solid specimen was 3D-printed and characterized for its mechanical, and geometrical accuracy. The maximum compressive strength obtained is 115 MPa for 20% ceramic loading, which then decreases with increased ceramic content. The biocompatibility test using MC3T3E1 cells confirmed zero cytotoxicity and cell grows well on all PLA and composite specimen. The results revealed that the composite biomaterials could be easily printed even at high ceramic loading and maintain their structural integrity and stability during the additive manufacturing process. These composites could be potential candidates for various biomedical applications, such as bone scaffolds and bioresorbable screws for Anterior Cruciate Ligament (ACL) reconstruction.

Biocomposites based on poly(lactic acid)/Aloe Vera/Priplast. Effects of UVA radiation on the crystallization

AbstractBiocomposites based on poly(lactic acid) (PLA), Aloe Vera (AV), and Priplast (Pr), were produced with AV and Pr levels of 5% and 10%, and submitted to UVA radiation for a time interval up to 28 days. Chemical changes were investigated using Fourier transform infrared spectroscopy (FTIR) and the thermal behavior was elucidated using differential scanning calorimetry (DSC); the non‐isothermal crystallization kinetics was modeled using the Pseudo‐Avrami model. FTIR spectra evidenced the formation of chromophore groups resulting from the photodegradation, which it was less intense in biocomposites with 10% Pr. AV addition promoted the cold crystallization, whereas the crystallization rate () displayed higher values for PLA/10%AV, with slight increases in the degree of crystallinity (Xc); while Pr addition decreased the Xc and of PLA, and protected it more intensely against the photodegradation effects. Pseudo‐Avrami model presented R2 ≥ 0.9909 and a low discrepancy between experimental and theoretical data, being adequate to describe the cold crystallization of PLA biocomposites. Summing up, AV and Pr addition protect PLA against the harmful effects of photodegradation, with AV subtly interfering in the crystalline parameters while Pr provides greater amorphicity to PLA biocomposites.

Self-assembled biobased chitosan hybrid carrying N/P/B elements for polylactide with enhanced fire safety and mechanical properties

The inherent shortcomings such as flammability, brittleness, and low crystallinity limit the broad applications of poly(lactic acid) (PLA). To improve the fire resistance and mechanical properties of PLA, a chitosan-based core-shell flame retardant additive (APBA@PA@CS) was prepared for PLA via the self-assembly of interionic interactions among chitosan (CS), phytic acid (PA), and 3-aminophenyl boronic acid (APBA). The peak heat release rate (pHRR) and total heat release rate (THR) of PLA composite containing 3 wt% APBA@PA@CS decreased from 460.1 kW/m2 and 75.8 MJ/m2 to 419.0 kW/m2 and 53.1 MJ/m2, respectively. The presence of APBA@PA@CS contributed to the formation of a high-quality char layer rich in phosphorus and boron in the condensed phase and released non-flammable gases in the gas phase to hinder the exchange of heat and O2, thereby having a synergistic flame retardant effect. Meanwhile, the tensile strength, elongation at break, impact strength, and crystallinity of PLA/APBA@PA@CS were increased by 3.7 %, 17.4 %, 5.3 %, and 55.2 %, respectively. This study provides a feasible route to construct a chitosan-based N/B/P tri-element hybrid to improve the fire safety performance and mechanical properties of PLA biocomposites.

Water absorption characterization of boron compounds-reinforced PLA/flax fiber sustainable composite

Biocomposites are widely used in construction, packaging, and automotive applications such as seatbacks, door panels, headliners, and dashboards, as well as industrial composting. The purpose of this study is to look into the effects of three different boron compounds (borax boric, acid combines, zinc borate, and ulexite) on the mechanical and microstructural properties of flax fiber/PLA biocomposites at different water uptake times. 7 different biocomposites were studied for this purpose: control, 3UF, 5UF, 3ZBF, 3BxBcF, 5BxBcF, and 5ZBF. Extrusion was used to create homogenous chopped flax fiber-reinforced PLA biocomposites, which were then injection molded. Alkali treatment on flax fiber surfaces was applied to improve interfacial adhesion between fiber and matrix. Water uptake tests were performed at room temperature for soaking times of 24, 50, 168, 240, 330, 480, 550, 600, and 750 h. The addition of boron compounds increases water gain from 4.4 % to 6.1 %, according to sorption results. The tensile elongation at break values of the composites increased slightly after short-term water absorption. SEM images showed that alkali-treated flax fibers and boron compounds dispersed uniformly in the PLA matrix. After 750 h of immersion, the addition of boron fillers to PLA/flax composite increased Young's Modulus and flexural modulus by about 50 % and 72 %, respectively, in comparison to the control composite sample. The addition of boric acid: borax combines into the PLA/flax composite slowed the rate of decline in tensile and flexural strength after various immersion times. Finally, using MINITAB software, the experimental results were subjected to a one-way analysis of variance (ANOVA).