Poly Lactic Acid Research Articles

Effect of Infill Patterns and Print Orientation on the Mechanical Properties of Manufactured Polylactic Acid Parts

Effect of Infill Patterns and Print Orientation on the Mechanical Properties of Manufactured Polylactic Acid Parts

Ultraviolet Protection and Antibacterial Properties of Polylactic Acid Nonwoven Fabrics Coated with Water-Borne Polyurethane/Zinc Oxide Composite Coatings

This study aimed to create thermally curable, water-borne polyurethane/zinc oxide (WPU/ZnO) composite coating pastes with varying ZnO concentrations. ZnO nanoparticles were synthesized using a wet chemical process, and the resulting WPU/ZnO coating pastes were applied to PLA nonwoven fabrics (NWFs). In characterization studies, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Fourier transform-infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) analyses were conducted. Ultraviolet (UV) protection and antibacterial activity of fabrics were investigated. With WPU/ZnO composite coatings, the UV protection properties of the coated fabrics were enhanced compared to the uncoated fabric. The highest UPF value of 53.57 was obtained with the fabric coated with the formulation containing a ZnO concentration of 10%. This fabric also demonstrated more effective antibacterial activity against both S. aureus and E. coli bacteria. Inhibition zone diameters against E. coli and S. aureus bacteria were measured as 15.5 ± 0.70 mm and 18.25 ± 0.35 mm, respectively. The results of this study illustrate that functional composite coatings for bio-based NWF structures hold great promise for producing effective UV protective and antibacterial materials, potentially setting the stage for future applications.

Novel insights into photoaging mechanisms and environmental persistence risks of polylactic acid (PLA) microplastics: Direct and indirect photolysis

Polylactic acid (PLA), as a biodegradable plastic, exhibits high sensitivity to ultraviolet (UV) radiation, yet the mechanisms and environmental risks of its photoaging remain unclear. This study uses quantum chemical calculations (DFT and TD-DFT) and kinetic simulations to explore the direct and indirect photoaging of PLA. Direct photoaging indicates that the highest oscillator intensity absorption peaks occurred at 172 and 246 nm, corresponding to the 13th singlet (S13) and 48th triplet (T48) states, thereby initiating the Norrish I and Norrish II mechanisms. The innovative “electron-hole” technology effectively clarifies the variations in photoaging mechanisms under different wavelengths. Indirect photoaging involves multiple reactive oxygen species (ROS) like •OH, 1O2, •O2−, and •HO2. The study confirms the anhydride production hypothesis and proposes two novel •OH-induced mechanisms: carbonyl carbon addition and branched methyl hydrogen dehydrogenation. Both mechanisms are thermodynamically advantageous, but their products pose potential environmental risks. ROS species and concentrations impact both PLA's photoaging mechanisms and environmental persistence. Low •OH concentration in northeast China, especially in winter, suggests a significant photoaging risk. This study offers pioneering insights into photoaging mechanisms and emphasizes the pivotal role of ROS, offering recommendations for managing PLA environmental impacts and fates in China.

Hierarchically Nano-Decorated Poly(lactic acid) Nanofibers for Humidity-Resistant Respiratory Healthcare and High-Accuracy Disease Diagnosis.

The application of biodegradable and eco-friendly poly(lactic acid) (PLA) nanofibrous membranes (NFMs) toward respiratory healthcare has long been thwarted by the poor electroactivity and low surface activity of PLA. Herein, we unravel a microwave-assisted route to fabricate rod-like ZnO nanodielectrics, which were decorated with dopamine (ZnO@PDA) and anchored at the PLA nanofibers via an electrospinning-electrospray approach. The PLA/ZnO@PDA NFMs featured a substantially elevated specific surface area (up to 20.7 m2/g), increased dielectric constant (nearly 1.8) and a surface potential as high as 9.5 kV, resulting in superior air filtering performance (99.45% for PM0.3, 94.1 Pa, 32 L/min) compared with the pure PLA counterpart (90.04%, 169.0 Pa, 32 L/min). The notably increased electroactivity endowed the PLA/ZnO@PDA NFMs with significant improvements in triboelectric properties (output voltage of 11.5 V at 10 N, 0.5 Hz), laying down the cornerstone for self-powered monitoring of personal respiration. More importantly, a deep learning-assisted diagnostic system was developed based on respiration-driven signal patterns, enabling intelligent and real-time disease diagnosis with 100% accuracy for the protective membranes. The proposed hierarchical nanodecoration strategy opens up new possibilities for engendering eco-friendly nanofibers with an exceptional combination of efficient respiratory healthcare and intelligent diagnosis.

Application of Response Surface Methodology Experimental Design to Optimize Tribological Lubrication Characteristics

Total Knee Replacement (TKR) has become a standard operation for patients with joint disorders. Despite the fact that the number of procedures is increasing all the time, the short service life of implants remains a persistent concern for researchers. Understanding lubrication may aid in explaining tribological processes that lead to replacements that last well into the third decade of service. Likewise, wear and friction in total knee replacement (TKR) components are among the most common causes of implant failure. As a result, this study will evaluate the feasibility of using the polymer Poly Lactic Acid (PLA) for cartilage replacement in Total Knee Replacement (TKR) using plant-based oils as lubricants. Furthermore, the modifier will be added to plant-based oils as an additive to make them analogous to human bodily fluids. The present paper is applying the Box-Behnken design to optimize the performance and mechanical responses of bio-lubricants toward Poly Lactic Acid (PLA) as a tibial insert for cartilage replacement in Total Knee Replacement (TKR). The main objective of this paper is to develop an optimized method for the selection of plant-based oil parameters using Response Surface Methodology (RSM). A three-level three-factor Box-Behnken design (BBD) was used to investigate the interactions between the essential factors comprising load (45 kg to 90 kg), speed (60 rpm, 90 rpm and 360 rpm), and concentration (0ml, 5ml and 10ml) of bio-lubricants to accomplish the indicated prospect of using polymer for cartilage replacement. Canola oil, castor oil, and sunflower seed oil are considered vegetable oils, whereas Hyaluronic Acid (HA) is the friction modifier. The parameters are used to create a Box-Behnken design for predicting lubricant anti-wear qualities stated in terms of coefficient of friction, wear rate and frictional force as determined by the pin-on-disk experimental procedure. As a result, the optimization using RSM successfully interpreted the experimental data, according to the analysis of variance, with coefficients of determination of R2 = 0.91 and adjusted R2 = 0.77. The Coefficient of Friction (CoF) and wear rate were investigated following tribological testing. Castor oil had a lower coefficient of friction than canola and sunflower seed oil, according to the findings. In terms of friction reduction, castor oil surpasses canola and sunflower seed oil.

Biocompatible Core-Shell Microneedle Sensor Filled with Zwitterionic Polymer Hydrogel for Rapid Continuous Transdermal Monitoring.

Microneedle (MN)-based electrochemical biosensors hold promising potential for noninvasive continuous monitoring of interstitial fluid biomarkers. However, challenges, such as instability and biofouling, exist. This study proposes a design employing hollow MN to encapsulate a zwitterionic polymer hydrogel sensing layer with excellent biocompatibility and antifouling properties to address these issues. MN shell isolates the internal microporous sensing layer from subcutaneous friction, and the hydrogel filling leverages the MNs' three-dimensional structures, enabling high-dense loading of biorecognition elements. The hollow MNs are successfully fabricated from high-molecular-weight polylactic acid via drawing lithography, exhibiting sufficient strength for effective epidermis penetration. Additionally, a high-performance gold nanoconductive layer is successfully deposited inside the MN hollow channel, establishing a stable electrical connection between the polymer MN and the hydrogel sensing layer. To support the design, numerical simulations of position-based diffusive analyte solutes reveal fast-responsive electrochemical signals attributed to the high diffusion coefficient of the hydrogel and the concentrated structure of the hollow channel encapsulation. Experimental results and numerical simulations underscore the advantages of this design, showcasing rapid response, high sensitivity, long-term stability, and excellent antifouling properties. Fabricated MN sensors exhibited biosafety, feasibility, and effectiveness, with accurate and rapid in vivo glucose monitoring ability. This study emphasizes the significance of rational design, structural utilization, and micro-nanofabrication to unlock the untapped potential of MN biosensors.

Thermal conductivity of 3D-printed block-copolymer-inspired structures

This study primarily focuses on examining the impact that geometric structure has on thermal conductivity of multi-phase constructs in different 3D-printed poly(lactic acid), PLA, samples. The investigated structures are inspired by morphologies formed by diblock copolymers: lamellae, hexagonally packed cylinders, and gyroid. This research also investigates how volume percentage and material combination influence the thermal conductivity of these structures. The samples can be tailored to simulate various thermal management structures observed in practical applications, such as thermal interface materials in electronic devices. Thermal conductivity ratio is controlled using air, the least conductive material at 0.026 W/(m K), PLA at 0.136 W/(m K), and thermal paste at 5.11 W/(m K). Different models were tested against thermal conductivity measurements in order to capture the effect of material type (PLA-Air versus PLA-Thermal Paste), volume percentage, structure, and orientation. Simple, effective medium models were good predictions of thermal conductivity in lamellar structures, but it was necessary to develop models for conduction through cylindrical and gyroid structures. Finally, all results were normalized to find a universal model that is independent of structure and material. This approach provides a simple method to predict how to reduce or enhance transport properties and heat management capabilities of 3D printed objects.

Simultaneously boosting the flame retardancy and degradability of poly(lactic acid) composite by phosvitin affiliation

Currently, it is still a challenge to endow polylactic acid (PLA) with excellent degradation and fire safety. In this work, we have extracted a novel phosvitin aiming to achieve the fire resistance and degradation of PLA. Employing the phosvitin, the PLA composite exhibits conspicuous fire resistance with an LOI of 27.4 % and a V-0 rating in the UL-94 tests by controlling the added volume at 40 wt.%. Simultaneously, the thermal stability and fire behaviour of the PLA composite have been improved by the plentiful char residue formation. The flame-retardant mechanism of phosvitin in PLA material has been deduced by TG-IR, FTIR XPS and SEM. The phosvitin containing abundant P-O, P = O and P-N functional groups generates phosphorus-containing compounds to promote the dehydration reaction of the PLA matrix in a condensed phase. This is beneficial to improve the flame retardancy of PLA by the formation of a char layer, providing the shielding effect to prevent the heat transfer and flammable micro-molecules volatilisation process. Likewise, the affluent phosphorus-containing compounds included in the phosvitin possess fabulous catalytic action to destroy the PLA into small molecular weight fragment which shows a beneficial to promote the degradation reaction of PLA composite. Hence, the phosvitin is important to expand the range of applications of PLA materials to develop sustainable multifunctional materials.

Enhancing functional properties of compostable materials with biobased plasticizers for potential food packaging applications

The demand of non-toxic and biobased plasticizers is substantially growing, particularly in biodegradable thermoplastics-based packaging applications. Herein, a derivative of citric acid (CITREM-LR10), usually used as food additive, was evaluated for the first time as plasticizer in PLA and Ecovio® biopolymers. Films containing 10 %(w/w) of CITREM-LR10 were prepared and compared with films plasticized with another biobased compound, SOFT-NSAFE, derived from acetic acid. The incorporation of both plasticizers provokes a slight reduction of the glass transition, however, only CITREM-LR10 was able to augment the elongation at break value of PLA films. A further evaluation of the films by Raman confocal microscopy showed the segregation of the CITREM-LR10 in microdomains, which could explain the enhanced elongation at break value, behaving as stress concentrators. In addition, CITREM-LR10 provides antimicrobial activity against S. aureus and both plasticizers give antioxidant properties, and almost negligible diffusion in food simulated solution. Composting studies showed that the plasticizers do not have effect on the disintegration rate of the films. In spite of these outstanding properties, the water vapour and oxygen barrier properties of the films worsen with its incorporation, therefore, the inclusion of fillers in the material together with the plasticizers would be necessary to improve such properties for food packaging applications.

An innovative functional compatibility strategy for poly (lactic acid) and polypropylene carbonate blends to achieve superior toughness, degradability, and optical properties

This study, for the first time, unveils the potential of dibutyl itaconate (DBI) in enhancing the compatibility between PLA (poly (lactic acid)) and PPC (polypropylene carbonate), systematically investigating the effects of DBI amount on the thermal, optical, rheological, mechanical, and degradation properties and microstructure of the PLA/PPC/DBI blends. The results showed that DBI could chemically react with PLA and PPC, forming a PLA-co-DBI-co-PPC copolymer structure, thereby improving the compatibility between PLA and PPC. When the DBI amount reached 8 wt%, only one Tg was observed in the blend system, and no distinct phase interface was visible in the fracture surface of the blend specimens. This indicated that at this DBI amount, the PLA and PPC had transitioned from a partially compatible system to a fully compatible system. With the increase in DBI amount in the system, the elongation at break and notched impact strength of the blends initially increased and then decreased, while the storage modulus, loss modulus, and complex viscosity showed a gradual downward trend. When the DBI amount increased to 10 wt%, the flexibility of the blends reached its peak, with the values rising to 494.7 % and 8494.1 J/m2, respectively, representing 13.7 times and 2.5 times those of the neat PLA/PPC blends. At this point, the impact specimens exhibited significant plastic flow in the direction of force, showing distinct ductile fracture characteristics. Meanwhile, the degradation performance of the PLA/PPC blends increased with the addition of DBI. The introduction of DBI effectively facilitated the penetration of water molecules into the PLA/PPC molecular chains, enhancing the hydrolysis of ester bonds, leading to a maximum mass loss rate of 84.1 %, which was significantly higher than the 20.3 % of the neat PLA/PPC blends. In addition, the addition of DBI significantly reduced the haze of the blends while maintaining high light transmittance, demonstrating excellent optical properties (light transmittance remained above 92.4 %, and haze decreased from 37.1 % to 11.1 %). In conclusion, this study provides a new approach for the development of high-performance PLA-based biodegradable composites. The resulting blends exhibit excellent toughness, degradation performance, and optical properties, significantly enhancing their application potential in fields such as disposable products, packaging, agriculture, and 3D printing materials.

Epitaxial crystallization of polylactic acid on layered zinc phenylphosphonate: Mutual perpendicular rodlike crystals under two lattice matchings

AbstractAs a highly effective nucleating agent, layered zinc phenylphosphonate (PPZn) is incorporated into polylactic acid (PLA) to investigate the epitaxial crystallization of PLA on PPZn in this study. The corresponding lattice spacing change, crystalline morphology, and crystalline structure are emphasized to reveal the epitaxial crystallization mechanism. As a result, with the increase of PPZn content and the annealing time, the increasing lattice spacing of PPZn and the formation of mutually perpendicular rodlike crystals are observed through x‐ray diffraction (XRD) and polarized optical micrograph (POM) measurements, implying that the interlayer spacing of PPZn crystals is expanded as the PLA α‐form crystals epitaxially grow on its surface, that is, epitaxial crystallization. To be specific, “edge on” lamellae epitaxial grow on the PPZn crystals along the [010] and [100] directions under two excellent lattice matchings, which possess acceptable mismatching of 0.347% and 7.5%, respectively. With the support of the epitaxial crystallization mechanism, the occurrence of the filamentous structure observed in the fracture morphology of PLA/PPZn composites suggests strong interfacial adhesion between PLA and PPZn, which makes the impact toughness of the PLA/PPZn composites increase by 53.6% compared with pure PLA.

Effect of Different Porous Size of Porous Inorganic Fillers on the Encapsulation of Rosemary Essential Oil for PLA-Based Active Packaging.

Essential oils are interesting active additives for packaging manufacturing as they can provide the final material with active functionalities. However, they are frequently volatile compounds and can be degraded during plastic processing. In this work Rosmarinus officinalis (RO) essential oil was encapsulated into Diatomaceous earth (DE) microparticles and into Halloysite nanotubes (HNTs) and further used to produce eco-friendly active packaging based on polylactic acid (PLA). PLA-based composites and nanocoposites films based on PLA reinforced with DE + RO and HNTs + RO, respectively, were developed by melt extrusion followed by cast-film, simulating the industrial processing conditions. As these materials are intended as active food packaging films, the obtained materials were fully characterized in terms of their mechanical, thermal and structural properties, while migration of antioxidant RO was also assessed as well as the compostability at laboratory scale level. Both DE and HNTs were able to protect the Rosmarinus officinalis (RO) from thermal degradation during processing, allowing to obtain films with antioxidant properties as demonstrated by the antioxidant assays after the materials were exposed for 10 days to a fatty food simulant. The results showed that incorporating Rosmarinus officinalis encapsulated in either DE or HNTs and the good dispersion of such particles into the PLA matrix strengthened its mechanical performance and sped up the disintegration under composting conditions of PLA, while allowing to obtain films with antioxidant properties of interest as antioxidant active food packaging materials.

Selective enrichment of high-risk antibiotic resistance genes and priority pathogens in freshwater plastisphere: Unique role of biodegradable microplastics

Microplastics (MPs) has been concerned as emerging vectors for spreading antibiotic resistance and pathogenicity in aquatic environments, but the role of biodegradable MPs remains largely unknown. Herein, field in-situ incubation method combined with metagenomic sequencing were employed to reveal the dispersal characteristics of microbial community, antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and virulence factors (VFs) enriched by MPs biofilms. Results showed that planktonic microbes were more prone to enrich on biodegradable MPs (i.e., polyhydroxyalkanoate and polylactic acid) than non-biodegradable MPs (i.e., polystyrene, polypropylene and polyethylene). Distinctive microbial communities were assembled on biodegradable MPs, and the abundances of ARGs, MGEs, and VFs on biofilms of biodegradable MPs were much higher than that of non-biodegradable MPs. Notably, network analysis showed that the biodegradable MPs selectively enriched pathogens carrying ARGs, VFs and MGEs concurrently, suggesting a strong potential risks of co-spreading antibiotic resistance and pathogenicity through horizontal gene transfer. According to WHO priority list of Antibiotic Resistant Pathogens (ARPs) and ARGs health risk assessment framework, the highest abundances of Priority 1 ARPs and Rank I risk ARGs were found on polylactic acid and polyhydroxyalkanoate, respectively. These findings elucidate the unique and critical role of biodegradable MPs for selective enrichment of high-risk ARGs and priority pathogens in freshwater environments.

Assessing the Stability and Photocatalytic Efficiency of a Biodegradable PLA‐TiO2 Membrane for Air Purification

AbstractThe potential of a biodegradable polylactic acid (PLA)‐TiO2 membrane for air purification is investigated, utilizing the environmentally friendly solvent Cyrene. Through the integration of TiO2 nanoparticles within a PLA matrix, the membrane is used to degrade ethanol as a model volatile organic compound (VOC) under UV light. Scanning Electron Microscopy (SEM), Energy Dispersive X‐ray Analysis (EDX), and UV–vis spectrophotometry confirm the porous structure of the membrane, the even distribution of TiO2, and its effective band gap of 3.06 eV, respectively. Ethanol adsorption is best described by the Langmuir isotherm model, suggesting monolayer coverage on a homogeneous surface. Photocatalytic tests demonstrate that the membrane decomposes ethanol (6800 ppm) within 14 min under UV light, generating acetaldehyde, acetic acid, formaldehyde, and formic acid as intermediates, and ultimately producing CO2 and water. Reusability tests indicate a decrease in decomposition time over successive cycles due to increased TiO2 exposure from the gradual degradation of PLA. However, this degradation poses challenges for continuous use, compromising the membrane's long‐term durability.

Cold crystallization behavior of poly(lactic acid) induced by poly(ethylene glycol)-grafted graphene oxide: Crystallization kinetics and polymorphism

Cold crystallization between the glass transition and melt temperature is of particular significance for crystalline regulation due to the slow crystallization rate of poly(lactic acid) (PLA). Incorporation of nucleation agents can promote PLA crystallization by reducing the nucleation activation energy and offering nucleation sites. Herein, we investigated the cold crystallization behavior of PLA induced by poly(ethylene glycol)-grafted graphene oxide (PEGgGO) which was synthesized and identified as a powerful nucleation agent for melt crystallization. The obtained results showed that PEGgGO not only accelerated the cold crystallization kinetics of PLA, but also promoted the polymorphic transition kinetics during the heating process. The half crystallization time of PLA induced by PEGgGO was shortened by 51 % and the final crystallinity increased by 57 % compared to that induced by GO alone at the same loading of 0.5 wt%. In addition, relative to GO, PEGgGO enabled the α′-to-α phase transition kinetics of PLA by a reduced transition temperature range of 26 % due to its excellent nucleation ability even at cold crystallization. The flexible PEG chains on GO facilitated crystalline regulation of PLA owing to the improved chain mobility. This work provides a broader framework for fashioning semicrystalline PLA products with enhanced crystallinity and refined crystal structure towards prospective applications.

Multiscale Imaging to Monitor Functional SHED-Supported Engineered Vessels.

Regeneration of orofacial tissues is hampered by the lack of adequate vascular supply. Implantation of in vitro engineered, prevascularized constructs has emerged as a strategy to allow the rapid vascularization of the entire graft. Given the angiogenic properties of dental pulp stem cells, we hereby established a preclinical model of prevascularized constructs loaded with stem cells from human exfoliating deciduous teeth (SHED) in a 3-dimensional-printed material and provided a functional analysis of their in vivo angiogenesis, vascular perfusion, and permeability. Three different cell-loaded collagen hydrogels (SHED-human umbilical vein endothelial cell [HUVEC], HUVEC with SHED-conditioned medium, and SHED alone) were cast in polylactic acid (PLA) grids and ectopically implanted in athymic mice. At day 10, in vivo positron emission tomography (PETscan) revealed a significantly increased uptake of radiotracer targeting activated endothelial cells in the SHED-HUVEC group compared to the other groups. At day 30, ex vivo micro-computed tomography imaging confirmed that SHED-HUVEC constructs had a significantly increased vascular volume compared to the other ones. Injection of species-specific lectins analyzed by 2-photon microscopy demonstrated blood perfusion of the engineered human vessels in both prevascularized groups. However, in vivo quantification showed increased vessel density in the SHED-HUVEC group. In addition, coinjection of fluorescent lectin and dextran revealed that prevascularization with SHED prevented vascular leakage, demonstrating the active role of SHED in the maturation of human-engineered microvascular networks. This preclinical study introduces a novel PLA prevascularized and implantable construct, along with an array of imaging techniques, to validate the ability of SHED to promote functional human-engineered vessels, further highlighting the interest of SHED for orofacial tissue engineering. Furthermore, this study validates the use of PETscan for the early detection of in vivo angiogenesis, which may be applied in the clinic to monitor the performance of prevascularized grafts.

A study of crashworthiness performance in thin‐walled multi‐cell tubes 3D‐printed from different polymers

AbstractMulticellular, thin‐walled impact tubes have been intensely studied and used in various engineering fields in recent years due to their lightweight, high performance, ease of application, superior energy absorption, and stable deformation characteristics. In this study, energy absorption, crashworthiness performances, and deformation properties of thin‐walled structures manufactured from polylactic acid (PLA+) and acrylonitrile butadiene styrene (ABS) using fused deposition modeling (FDM) technology were compared under quasi‐static axial compression. Thin‐walled structures consist of multicellular tubes connected by concentric corner‐edge connections with square and hexagonal cross‐sections. Experimental testing outcomes indicate that the energy absorption capacity increases with increasing the number of corners in multicellular structures. The tubes with square wall‐to‐wall (S‐WW) and hexagonal wall‐to‐wall (H‐WW) cross‐sections exhibit superior crashworthiness performance compared to other cross‐sections. Based on the experimental results, the absorbed energy by WW patterned PLA+ square tubes are 19%, 7%, and 46% more than that of wall‐to‐corner (WC), corner‐to‐wall (CW), and corner‐to‐corner (CC) patterned tubes, respectively, while it is 11%, 19%, and 80% more in hexagonal cross‐section tubes, respectively. This study provides an informative reference for easier applicability of multicellular energy‐absorbing structures with 3D‐print and the design of corner‐edge connections of internal connections in multicellular structures.

Design, Simulation, and Fabrication of Composite Lattice Orthoses with Enhanced Structural Performance

Abstract Orthoses play a critical role in rehabilitation by providing fracture stabilization, external load protection, and deformity correction. Traditional methods of orthotic manufacturing often result in reduced breathability leading to potential skin problems, and increased bulkiness and weight due to material and processing limitations. Method: This study aims to enhance breathability and structural performance of orthoses through the utilization of a fiber-reinforced composite lattice design fabricated using a Coreless Filament Winding (CFW) process. An arm brace was designed and manufactured, which incorporates four modules made of fiberglass/polystyrene composite lattices assembled together using adjustable thermoplastic connectors. To simulate the structural performance, a Finite Element Model (FEM) was constructed with careful consideration of the interactions between the connectors and the lattice modules, and this was subsequently validated through experiment. Results: In comparison to a benchmark brace made of Polylactic Acid (PLA) lattice, the composite brace exhibits a significant reduction in thickness (60%) and weight (44%) while maintaining equivalent structural performance. The validation test indicates the FEM's reliability in predicting structural stiffness and strength, with the predicted peak loading being slightly conservative (5%) compared to experimental results. Conclusion: Composite lattice structures represent a significant advancement in the design of breathable, lightweight, and high-strength orthoses. Moreover, the developed FEM serves as a valuable tool for accurately predicting structural performance and optimizing orthotic design under varying loading conditions.

Effect of carboxymethylated chitosan and cellulose acetate on mechanical properties of PLA blends for biomedical applications

Chitin and chitosan are versatile and valuable biomaterials, with chitosan being abundantly found in the exoskeletons of crustaceans, insects, arthropods, and mollusks. The chemical extraction of chitin involves a series of steps, including deproteinization, demineralization, and decolorization. Chitosan is often combined with various polymeric materials, and polymer blending can enhance the mechanical properties of the resulting bioproduct. In this study, composites of poly(lactic acid) (PLA) with chitosan (Ch) and cellulose acetate (CA) were successfully fabricated using extrusion and injection molding techniques. The chitosan content, ranging from 0 to 7.5 wt. %, was incorporated into the PLA matrix to assess the impact of filler content on the mechanical and morphological properties of the composites. The chitosan powder was first alkalized and then etherified to obtain modified chitosan, specifically o-carboxymethylated chitosan (O-CMCh). The addition of chitosan led to a reduction in tensile strength, flexural strength, modulus of elasticity, and impact strength. However, the hardness of the composite improved with the inclusion of chitosan. The mesoporous structure of chitosan was characterized using nitrogen adsorption and desorption measurements. Morphological analysis revealed that the composite containing 3.75 wt. % chitosan exhibited significantly less fracture surface compared to other composites.

Continuous oxidation of organic contaminates in soil by polylactic acid-coated KMnO4

Potassium permanganate (KMnO4), as a versatile and safe solid source of MnO4-, received substantial attention from researchers as a potential soil oxidant reagent. In this study, we prepared polylactic acid (PLA)-coated KMnO4 (KMnO4@PLA) to control MnO4- release. The experimental results indicated that the optimal preparation scheme for KMnO4@PLA was a particle size of 1–2 mm, a solid-liquid ratio of 1:3, and a core-shell ratio of 1:3. And the release lifetimes of MnO4- from KMnO4@PLA in aqueous and quartz sand media were 200 hours and 310 hours, respectively, which were 2400 and 33 times longer than the release lifetimes of raw KMnO4. The controlled release of MnO4- from KMnO4@PLA was achieved through the hydrolysis of PLA. And the release process adhered to first-order reaction kinetics and displayed Fickian diffusion characteristics. Moreover, the removal of phenol by KMnO4@PLA in aqueous, quartz sand, and soil media were investigated through batch and flow column experiments. Compared with the raw KMnO4, the KMnO4@PLA exhibited a stronger ability to degrade phenol, due to the mildly acidic nature of the PLA shell. These findings demonstrated that KMnO4@PLA has significant advantages for the remediation of organically contaminated soils.