Crystallinity Of Polylactic Acid Research Articles

The effect of polylactic acid ordering on the long-term corrosion protection capacity of biodegradable magnesium alloys

The polylactic acid (PLA) coatings of different crystallinity were prepared on biodegradable Mg-2.2Zn-0.3Ca alloy wires to improve the long-term anti-corrosion properties. The composition characteristics and microstructure of the samples were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscope (FTIR), wide angle X-ray diffraction (WAXD) and scanning electron microscope (SEM). The corrosion resistance of all samples was investigated by immersion tests and electrochemical techniques in vitro simulated body fluid (SBF). The results indicated heat treatment improved the crystallinity of PLA coating and heated-coating performed protective behaviors in the short and long-term immersion. The corrosion rate of heated samples was lower than that of unheated samples and exhibited superior long term protective effect for Mg alloy wires. The lifetime of heated sample (H2) increased significantly from 33 to 55 days. The initial electrochemical performance of unheated coating was better than heated coating, but it declined more rapidly during the long-term immersion. These results indicated that PLA coating could not ignore the effect of its crystallinity to anti-corrosion ability, and only the suit heat treatment makes PLA coating more ordering and achieves higher corrosion resistance in vitro immersion. Therefore, it has promising potential by controlling effectively the PLA ordering for surgical implant applications.

Confinement Effect in Multilayer Films Made from Semicrystalline and Bio-Based Polyamide and Polylactic Acid.

Bio-based multilayer films were prepared by using the innovative nanolayer coextrusion process to produce films with a number of alternating layers varying from 3 to 2049. For the first time, a semicrystalline polymer was confined by another semicrystalline polymer by nanolayering in order to develop high barrier polyamide (PA11)/polylactic acid (PLA) films without compromising thermal stability and mechanical behavior. This process allows the preparation of nanostratified films with thin layers (down to nanometric thicknesses) in which a confinement effect can be induced. The stratified structure has been investigated, and the layer thicknesses have been measured. Barrier properties were successfully correlated to the microstructure, as well as the thermal behavior, and mechanical properties. The layer continuity was fully achieved for most of the films, but some layer breakups have been observed on the film with the thinnest PLA layer (2049-layers film). Coextruding PLA with PA11 has induced an increase in PLA crystallinity (from 4 to 16%) along with an increase in thermal stability of the multilayer films without impacting PA11 properties. Gas barrier properties were driven by the PLA confined layers due to the microstructural rearrangement by increasing crystallinity, whereas water barrier properties were governed by the PA11 confining layers due to its lower water affinity. As a consequence, a decrease of water permeability (up to 11 times less permeable for the 6M film) but an increase of gas barrier properties (barrier improvement factor (BIF) of 66% for the 0M film for N2 and BIF of 36% for the 6M film for CO2 for instance) were evidenced as the layer number was increased. This study paves the way for the development of ecofriendly materials with outstanding barrier performances and highlights the importance of nonmiscible polymers adhesion at melt state and additives presence.

Enhanced Crystallization of Sustainable Polylactic Acid Composites Incorporating Recycled Industrial Cement.

Globally, the demand for single-use plastics has increased due to the rising demand for food delivery and household goods. This has led to environmental challenges caused by indiscriminate dumping and disposal. To address this issue, non-degradable plastics are being replaced with biodegradable alternatives. Polylactic acid (PLA) is a type of biodegradable plastic that has excellent mechanical properties. However, its applications are limited due to its low crystallinity and brittleness. Studies have been conducted to combat these limitations using carbon or inorganic nucleating agents. In this study, waste cement and PLA were mixed to investigate the effect of the hybrid inorganic nucleating agent on the crystallinity and mechanical properties of PLA. Waste cement accelerated the lamellar growth of PLA and improved its crystallinity. The results indicate that the flexural and impact strengths increased by approximately 3.63% and 76.18%, respectively.

Supertoughened Polylactic Acid/Polybutylene Adipate Terephthalate Blends Compatibilized with Ethylene-Methyl Acrylate-Glycidyl Methacrylate: Morphology and Mechanical Properties by the Response Surface Methodology.

Optimized extrusion melt-blending of polylactic acid (PLA) polymer with a minor biopolymeric phase, polybutylene adipate terephthalate (PBAT), and compatibilized with random ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMA-GMA, Trademark: Lotader AX-8900) led to an outstanding improvement in mechanical properties. At the noncompatibilized PLA-PBAT (80-20) blend point, significant enhancement (∼4500%) in toughness and elongation-at-break was already obtained without compromising any elastic properties. The effect of the compatibilizer content on the mechanical properties of the PLA-PBAT (80-20) blend was investigated by an optimal custom response surface methodology. Thus, 2 wt % Lotader content was determined to be optimal by a numerical optimization methodology with a desirability value, D, of 0.882 to maximize toughness and elongation-at-break. The compatibilization and thermal behavior of the Lotader-modified blends were analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Upon adding the compatibilizer, the original phase-separated morphology of the blends changed from PBAT quasi-spherical domains to nearly elongated elliptical ones. It was also found that the interfacial boundary line of the domains faded away, which revealed that interfacial compatibility was achieved. The thermostability of the blends remained largely unaltered following the incorporation of PBAT and Lotader. Moreover, while PBAT exhibited a minor influence on the crystallinity of PLA, Lotader had no discernible impact on crystallinity, as evidenced by the DSC thermograms. Thus, the compatibilizer at the optimal point in the optimized blend ratio led to the formation of a phase-separated morphology that combined internal cavitation, interfacial cavitation, and strong adhesion features at the right proportions in the microstructure which underlies the micromechanisms driving the remarkable enhancement of as much as 7100% in toughness and ductility.

Characterization of biodegradable bi‐layer films from thermoplastic starch and poly‐l‐lactic acid

AbstractThis study aimed to enhance the oxygen barrier properties of polylactic acid (PLA) film, a biodegradable packaging material with high oxygen permeability (OP). Bi‐layer films were produced by coating thermoplastic starch (TPS) onto PLA films in various ratios while maintaining constant film thickness. The mechanical, optical, barrier, thermal, hydrophobicity, moisture sorption, and microstructural properties of the films were analyzed. Increasing the TPS ratio elevated moisture content (MC), water uptake, solubility, and opacity while enhancing UV barrier properties. TPS coating reduced tensile and burst strength but increased the burst deformation of the bi‐layer films. Bi‐layer film production resulted in a water vapor permeability increase of 59.26%–94.44% compared with neat PLA while decreasing OP by 2.52%–29.66%. The equilibrium moisture content (EMC) rose with higher TPS ratios, displaying type II isotherms. FTIR analysis indicated no chemical interactions between PLA and TPS. Increasing the TPS ratio decreased PLA crystallinity, supporting the mechanical and barrier properties of the bi‐layer films. Neat and bi‐layer films exhibited smooth, homogeneous surfaces, with a visible interface in the cross‐section of the bi‐layer films. In conclusion, TPS shows promise as an alternative to improve oxygen barrier properties in PLA films without adversely affecting other properties.

A study of the mechanical, thermal and rheological properties of sisal fiber-reinforced polylactic acid bio-composites with tributyl 2-acetylcitrate as a plasticizer

In this study, bio-composites were developed using polylactic acid (PLA) as the matrix and sisal fibers (SFs) derived from agave sisalana leaves as the reinforcement. The bio-composites were prepared through injection molding with the addition of tributyl 2-acetylcitrate (ATBC) plasticizer. The mechanical, thermal, and rheological properties of these bio-composites were investigated to understand the effects of fiber and plasticizer contents. The results showed that the addition of SFs improved the tensile and flexural moduli of the bio-composites but led to a decrease in tensile strength compared to neat PLA. The flexural strength initially decreased with low fiber content but recovered to the level of neat PLA as the fiber content increased. The impact strength increased with the incorporation of SFs and ATBC. However, the presence of ATBC had a negative impact on the tensile and flexural properties of the bio-composites. The thermal conductivity of the materials was influenced by the fiber content and processing temperature, increasing with SFs inclusion but decreasing with temperature. Differential scanning calorimetry analysis revealed increased crystallinity of PLA with the presence of SFs and ATBC. The specific heat capacity increased with ATBC but decreased with increasing SFs. Dynamic mechanical property testing showed variations in storage and loss moduli of the bio-composites at different temperatures. The storage modulus increased with higher fiber content and abruptly dropped around glass transition temperature. Rheological characterization demonstrated effective interactions between the fibers and matrix with good fiber dispersion, resulting in uniform shear viscosity versus shear rate for different capillary dimensions. The shear viscosity of the SFs/PLA mixture increased with increasing fiber content but decreased with the addition of plasticizer. Furthermore, the compounding and molding processes had a notable impact on the microstructure of the fibers, specifically resulting in fiber breakage and fiber separation during processing.

Effect of Polybutylene Succinate Additive in Polylactic Acid Blend Fibers via a Melt-Blown Process.

This work aimed to study the influence of the polybutylene succinate (PBS) content on the physical, thermal, mechanical, and chemical properties of the obtained polylactic acid (PLA)/PBS composite fibers. PLA/PBS blend fibers were prepared by a simple melt-blown process capable of yielding nanofibers. Morphological analysis revealed that the fiber size was irregular and discontinuous in length. Including PBS affected the fiber size distribution, and the fibers had a smoother surface with increased amounts of added PBS. Differential scanning calorimetry analysis (DSC) revealed that the crystallization temperature of the PLA sheet (105.8 °C) was decreased with increasing PBS addition levels down to 91.7 °C at 10 wt.% PBS. This suggests that the addition of PBS may affect PLA crystallization, which is consistent with the X-ray diffraction analysis that revealed that the crystallinity of PLA (19.2%) was increased with increasing PBS addition up to 28.1% at 10 wt% PBS. Moreover, adding PBS increased the tensile properties while the % elongation at break was significantly decreased.

Green biodegradable dielectric material made from PLA and electron beam irradiated luffa cylindrica fiber: devices for a sustainable future.

The growing prevalence of polymer-based plastics in the environment is an imminent risk to the natural world. As an immediate consequence of this, extensive research has been launched over the course of the past few decades in an effort to reduce the damage that manmade plastics cause to the natural environment. The current study attempts to explore the biodegradability of polylactic acid (PLA), a bio-compatible plastic, by incorporating small amount of electron beam irradiated natural fibers (2 to 10%) derived from luffa cylindrica (LC) at varying irradiation doses (0.5 Gy, 1 Gy, and 2 Gy). Natural fiber surface treatment using electron beam irradiation is effective and environmentally friendly. The biodegradation of composites was studied for 90 days in sand, soil, compost, brackish water, fresh water, salt water, and bacterial and fungal conditions. Maximum decomposition was observed in the composite sample (PLA/10% wt of LC fiber at 2.0 Gy) at 15.42% and 4.73% in bacterial and soil environments. X-ray diffraction (XRD) and Raman spectroscopy validated the fiber and PLAs crystallinity and molecular interaction. The derivative thermo-gravimetric curve (DTGA) showed that electron beam irradiation removed moisture, hemicelluloses, and lignin from hydrophilic fibers. The incorporation of LC fibers into the bio-composites resulted in an increase in the glass transition temperature (Tg), melting temperature (Tm), and crystallization temperature (Tc). Additionally, after LC fiber reinforcement, the composites' dielectric properties were enhanced.

Enhancing interfacial interaction and crystallization in polylactic acid-based biocomposites via synergistic effect of wood fiber and self-assembly nucleating agent

Incorporation of natural fibers into polylactic acid (PLA) provides a feasible pathway to improve the performance of PLA with a low environmental impact. However, the insufficient interfacial adhesion between fiber and matrix limits the reinforcement efficiency of fiber and final mechanical properties of the biocomposites. Herein we reported an efficient method to simultaneously enhance interfacial interaction, crystallization and mechanical performance of PLA-based biocomposites via combination of wood fiber (WF) and a self-assembly nucleating agent (TMC-300). The interactions between WF and TMC-300 and its influence on PLA, including interfacial crystal morphology, crystallization behavior, and mechanical performance were studied. The results showed that TMC-300 could self-assemble into dendritic-like structure on WF surface driven by hydrogen bonding, inducing the epitaxial crystallization of PLA. This unique interfacial crystallization integrated PLA matrix with WF, resulting in better interfacial adhesion. Under the optimal TMC-300 content (0.5 wt%), the flexural strength and notched impact strength of PLA composites increased by 10 % and 69 % compared with neat PLA, respectively. Additionally, TMC-300 and WF synergistically functioned as effective nucleating agents, which significantly accelerated the crystallization rate and improved the crystallinity of PLA. This work provides a new insight into the enhancement of interfacial bonding in natural fiber/PLA biocomposites.

Pushing the limits of PLA by exploring the power of MWCNTs in enhancing thermal, mechanical properties, and weathering resistance

The present study focuses on enhancing the mechanical, thermal, and degradation behavior of polylactic acid (PLA) by adding carbon nanotubes (CNTs) with different concentrations of 0.5, 1, 3, and 5%. The CNTs were prepared using catalytic chemical vapor deposition, and the prepared PLA/CNTs nanocomposite films were characterized using techniques such as FT-IR, Raman spectroscopy, TGA, SEM, and XRD. The distinct diffraction patterns of multi-walled carbon nanotubes (MWCNTs) at 2θ angles of 25.7° and 42.7° were no longer observed in the prepared nanocomposites, indicating uniform dispersion of MWCNTs within the PLA matrix. The presence of MWCNTs enhanced the crystallinity of PLA as the CNT loading increased. Mechanical tests demonstrated that incorporating CNTs positively influenced the elongation at the break while decreasing the ultimate tensile strength of PLA. The PLA-3%CNTs composition exhibited the highest elongation at break (51.8%) but the lowest tensile strength (64 MPa). Moreover, thermal gravimetric analysis confirmed that the prepared nanocomposites exhibited greater thermal stability than pure PLA. Among the nanocomposites, PLA-5% CNTs exhibited the highest thermal stability. Furthermore, the nanocomposites demonstrated reduced surface degradation in accelerated weathering tests, with a more pronounced resilience to UV radiation and moisture-induced deterioration observed in PLA-3% CNTs.

3D printing of cellulose nanofiber/polylactic acid composites via an efficient dispersion method

In this study, a green and efficient dispersion method was developed to prepare cellulose nanofiber (CNF) reinforced polylactic acid (PLA) composites for fused deposition modeling (FDM) 3D printing. The CNF/PLA compounds were readily obtained by blending a CNF aqueous suspension with microscale PLA powder, followed by an air-drying process. This method significantly reduced the need for chemical reagents and shortened the processing time. A silane coupling agent and polyethylene glycol (PEG) were used as surface modifiers to enhance the dispersion of CNFs in PLA matrix, and the interfacial interactions between the two constituents in the composite. The CNF/PLA composite filaments for 3D printing were produced using twin-screw cycling extrusion. The test results showed that the incorporation of the surface-modified CNFs effectively enhanced the flowability and the mechanical performance of PLA. The superior mechanical properties of the resulting 3D-printed CNF/PLA composites can be attributed to the uniform dispersion of CNFs in the PLA matrix, higher crystallinity of PLA, and reduced composite defects.

A strategy to prepare high‐robust and ultra‐tough polylactic acid/polycaprolactone/talc composites with thermo‐resistance

AbstractBlending with ductile polycaprolactone (PCL) is one of the common toughening methods for polylactic acid (PLA). However, it seems inevitable to experience a trade‐off in mechanical strength and thermal stability of PLA. Therefore, this study aimed to improve the mechanical and thermal properties of PLA/PCL blends by adding different contents of talc (0–10 wt%) and conducting annealing treatments. Interestingly, the maximum tensile strength (52.04 MPa), elongation at break (83.51%), and impact strength (6.05 kJ/m2) were achieved by incorporating 2.5 wt% talc into the blends without annealing. Meanwhile, the addition of just 1 wt% talc shortened the semi‐crystallization time of PLA to one‐third of the neat PLA at 100°C. Particularly, after annealing treatment, the crystallinity of PLA increased to 32.1%, and the Vicat softening temperature reached as high as 133.3°C with 2.5 wt% talc. Importantly, the increase in crystallinity did not compromise the toughness of PLA composites but significantly enhanced the impact strength to 8.91 kJ/m2. This study provides an updated understanding of the relationship between toughness and crystallinity in PLA composites.Highlights Thermo‐resistance of polylactic acid (PLA) composite increases to 133.3°C. Talc aids nucleation and promotes PLA crystallization. Increased crystallinity and high toughness are simultaneously realized. Adding 1 wt% talc reduced PLA semi‐crystallization time by one‐third. Crystal transformation and sea‐islands structure are vital for reinforcements.

Effect of Spent Coffee Grounds on the Crystallinity and Viscoelastic Behavior of Polylactic Acid Composites.

This work investigated the addition of spent coffee grounds (SCG) as a valuable resource to produce biocomposites based on polylactic acid (PLA). PLA has a positive biodegradation effect but generates poor proprieties, depending on its molecular structure. The PLA and SCG (0, 10, 20 and 30 wt.%) were mixed via twin-screw extrusion and molded by compression to determine the effect of composition on several properties, including mechanical (impact strength), physical (density and porosity), thermal (crystallinity and transition temperature) and rheological (melt and solid state). The PLA crystallinity was found to increase after processing and filler addition (34-70% in the 1st heating) due to a heterogeneous nucleation effect, leading to composites with lower glass transition temperature (1-3 °C) and higher stiffness (~15%). Moreover, the composites had lower density (1.29, 1.24 and 1.16 g/cm3) and toughness (30.2, 26.8 and 19.2 J/m) as the filler content increased, which is associated with the presence of rigid particles and residual extractives from SCG. In the melt state, polymeric chain mobility was enhanced, and composites with a higher filler content became less viscous. Overall, the composite with 20 wt.% SCG provided the most balanced properties being similar to or better than neat PLA but at a lower cost. This composite could be applied not only to replace conventional PLA products, such as packaging and 3D printing, but also to other applications requiring lower density and higher stiffness.

Sewage sludge induces changes in the surface chemistry and crystallinity of polylactic acid and polyethylene films

Plastic pollution is a major threat facing our environment. To understand the full effects, we must first characterize how plastics break down in environmental systems. Heretofore, there has been little work examining how exposure to sewage sludge facilitates the degradation of plastics, particularly of plastics that have been previously weathered. Herein, we characterize how the crystallinity, surface chemistry, and morphology of polylactic acid (PLA) and polyethylene (PE) films change due to sludge exposure. In this work, sludge-induced changes in carbonyl index were found to depend on the level of prior exposure to ultraviolet (UV) irradiation. The carbonyl indices of un-irradiated films increased while those of UV-aged films decreased after 35 days of sludge exposure. In addition, the carbon‑oxygen and hydroxyl bond indices of PE films increased with sludge exposure, suggesting the surface oxidation of PE. As for PLA, crystallinity was found to increase with sludge exposure, consistent with a chain scission mechanism. This work will help to predict the behavior of plastic films after transfer from wastewater to sewage sludge.

Process parameters optimization and mechanical properties of 3D PLA/HA printing scaffold

This research aimed to study the mechanical properties, specifically the compressive strength of Polylactic Acid (PLA)/Hydroxyapatite (HA) cell scaffolds obtained by 3D printing, and to find the relationship of factors used in the synthesis of PLA/HA cell scaffolds obtained by 3D printing. The PLA/HA filaments with glycerol as a binder were formed at an optimal condition of tensile strength by 5 wt% HA and a melting temperature of 170 °C with a screw rotation speed of 25 revolutions per minute. The highest tensile strength of synthetic filaments was 35.12 MPa. Then, the central composite design was designed using three factors, nozzle temperature, printing speed, and the density of the forming specimens. Then, 3D-forming specimens were fabricated to be examined for compressive strength. Effective factors and optimal levels were analyzed by Minitab statistic software. The optimal factor level was refabricated, and the annealed process was also applied to improve its mechanical properties. Annealed and Unannealed specimens’ compressive strengths were compared. The results showed that a nozzle temperature of 215 °C and a part density of 100% had the most affected on maximum compressive strength at 65.62 MPa. The printing speed had no significant effect. Furthermore, a differential scanning calorimeter (DSC) was used to study the properties and the degree of crystallinity of PLA. The result found that the crystallization of a PLA was increased by an annealing treatment that affects heat resistance and also increases compressive strength by 11.60% compared to unannealed specimens.

나노셀룰로오스 분말 개발과 폴리젖산 내 핵제 적용 연구

Because of the global pollution caused by plastic disposal, demand for eco-friendly transformation in the packaging industry is increased. As part of that, the utilization of polylactic acid (PLA) as a food packaging material is increased. However, it is necessary to improve the crystallinity of PLA by adding nucleating agents or to improve the modulus by adding fillers because of the excessive brittleness of the PLA matrix. Thus, the cellulose nanofiber (CNF) was fabricated and dried to obtain a powder form and applied to the CNF/PLA nanocomposite. The effect of CNF on the morphological, thermal, rheological, and dynamic mechanical properties of the composite was analyzed. We can confirm the impregnated CNF particle in the PLA matrix through the field emission scanning electron microscope (FESEM). Differential scanning calorimetry (DSC) analysis showed that the crystallinity of not annealed CNF/PLA nanocomposite was increased approximately 2 and 4 times in the 1st and 2nd cycle, respectively, with the shift to lower temperature of cold crystallization temperature (Tcc) in the 2nd cycle. Moreover, the crystallinity of annealed CNF/PLA nanocomposite increased by 13.4%, and shifted Tcc was confirmed.

Achieving high mechanical properties of biodegradable vascular stents by four-axis 3D printing system and heat treatment

This study fabricated biodegradable polylactic acid (PLA) stents with extremely smooth surfaces by a four-axis printing system. Isothermal heat treatment has been carried out on the 3D-printed stent in a salt bath. The crystallinity of PLA has increased by 212% after heat treatment. Compared to the untreated stent, the heat-treated stent has an 11% higher radial supporting stiffness and a 33% higher maximum radial supporting load. The stent can also withstand bending deformation more safely by eliminating residual strain through heat treatment. These results suggest that the isothermal heat treatment is an effective technique for enhancing the load-bearing capacities of 3D-printed PLA stents.

Preparation and Properties of Graft-Modified Bagasse Cellulose/Polylactic Acid Composites

ABSTRACT Fiber reinforcement is the most common method for modifying polylactic acid (PLA). However, poor compatibility between fibers and PLA, especially at high cellulose contents, can promote cellulose agglomeration in the continuous phase, which damages the mechanical properties of composite materials. To address these issues, bagasse cellulose (BC) was used as a substrate and bifunctional glycidyl methacrylate (GMA) was used as a reactive monomer for graft modification. GMA-modified BC (BC-GMA)/PLA composite materials with different particle sizes were prepared using a blending grafting method, and the influence of the type and content of BC-GMA on the mechanical properties of the composite materials was explored. During the grafting modification of BC, a longer reaction time was found to result in smaller BC particles and a higher degree of grafting. For BC-GMA, the degree of grafting reached 27.02% with a maximum thermal decomposition temperature of 359.31°C. Furthermore, the BC-GMA/PLA composite material had a greater relative crystallinity of PLA, indicating that BC-GMA was evenly dispersed in the continuous phase. This study demonstrates that grafting modification can successfully achieve high cellulose loading in composite materials and thus reduce the production costs of PLA-based packaging materials.

Thermomechanical Properties and Biodegradation Behavior of Itaconic Anhydride-Grafted PLA/Pecan Nutshell Biocomposites.

The use of lignocellulose-rich biowaste as reinforcing filler in biodegradable polymers represents a sustainable option to obtain cost-effective bio-based materials to be used for several applications. In addition, the scarce polymer-biofiller interaction can be improved by reactive functionalization of the matrix. However, the obtained biocomposites might show high thermal deformability and possibly a slow biodegradation rate. In this work, polylactic acid (PLA) was first chemically modified with itaconic anhydride, and then biocomposites containing 50 wt.% of pecan (Carya illinoinensis) nutshell (PNS) biowaste were prepared and characterized. Their physical and morphological properties were determined, along with their biodegradation behavior in soil. Moreover, the effects of two environmentally friendly physical treatments, namely ball-milling of the filler and thermal annealing on biocomposites, were assessed. Grafting increased PLA thermal-oxidative stability and crystallinity. The latter was further enhanced by the presence of PNS, achieving a 30% overall increase compared to the plain matrix. Accordingly, the biocomposites displayed mechanical properties comparable to those of the plain matrix. Thermal annealing dramatically increased the mechanical and thermomechanical properties of all materials, and the heat deflection temperature of the biocomposites dramatically increased up to 60 °C with respect to the non-annealed samples. Finally, PNS promoted PLA biodegradation, triggering the swelling of the composites under soil burial, and accelerating the removal of the polymer amorphous phase. These results highlight the potential of combining natural fillers and environmentally benign physicochemical treatments to tailor the properties of PLA biocomposites. The high biofiller content used in this work, in conjunction with the chemical and physico-mechanical treatments applied, increased the thermal, mechanical, and thermomechanical performance of PLA biocomposites while improving their biodegradation behavior. These outcomes allow for widening the application field of PLA biocomposites in those areas requiring a stiff and lightweight material with low deformability and faster biodegradability.

The Influence of Different Sustainable Silk-Based Fillers on the Thermal and Mechanical Properties of Polylactic Acid Composites.

In this work, different silk fillers combined with maleinized corn oil (MCO), as environmentally friendly plasticizers, were used to modify the mechanical and thermal properties of polylactic acid (PLA) composites. Melt extrusion and injection were used to obtain samples with a content of 10 wt.% of MCO and 0.5 phr of different silk fillers: crushed silk (CS), silk fibroin microparticles (SFM), and silk fibroin nanoparticles (SFN). PLA formulation with 10 wt.% of MCO and 0.5 g of CS per hundred grams of composite (phr) showed the highest increase in mechanical ductile properties with an increase in elongation at break of approximately 1400%, compared with PLA. Differential scanning calorimetry (DSC) showed a decrease of 2 °C in their glass transition temperature with the addition of different silk fillers. In addition, SFM and SFN increase the degree of crystallinity of PLA. This increment was also confirmed by infrared spectroscopy analysis. Field emission scanning electron microscopy (FESEM) images revealed a good dispersion of the different silk fillers. Among them, PLA formulation with 10 wt.% MCO and 0.5 phr of SFN, showed an optimal balance between maximum resistance and elongation at break, with 52.0 MPa and 10.8%, respectively, improving elongation at break by 635%. Furthermore, all samples were satisfactorily disintegrated under composting conditions.