Poly Lactic Acid Research Articles

Mechanistic insight into interactive effect of microplastics and arsenic on growth of rice (Oryza sativa L.) and soil health indicators

Microplastics (MPs) pollution has recently become a major concern for agroecosystems. The interplay between MPs, and heavy metal(loid)s in the soil can intensify the risks to plant growth and human health. The current study investigated the interactive effects of arsenic (As) and biodegradable and petroleum-based conventional MPs on rice growth, As bioavailability, soil bacterial communities, and soil enzyme activities. As-contaminated soil (5 mg kg−1) was treated with conventional MPs i.e., polystyrene (PS) and polyethylene (PE) and biodegradable MPs i.e., polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) at 0.1 % and 1 % rates. In a pot experiment, rice plants were cultivated in soil co-contaminated with As and MPs. PLA-MPs exhibited significant interactions with As, increasing its bioavailability and impairing rice plant growth by enhancing plant oxidative stress. The results illustrated that T2 treatment (PLA-MPs @ 1 % + As 5 mg kg−1) significantly decreased the root and shoot lengths, root and shoot dry weights as well as the rates of photosynthesis, transpiration, intercellular CO2, and stomatal conductance in rice plants. Biodegradable PLA-MPs @ 1 % resulted in increased uptake of As in rice roots, stems, and leaves by 13.4 %, 38.9 %, and 20.6 %, respectively. In contrast, conventional PE-MPs @ 1 % showed contradictory results with As uptake declined by 2.2 %, 5.1 %, and 9.9 % in rice roots, stem and leaves. Soil enzyme kinetics showed that biodegradable MPs increased the activities of soil catalase, dehydrogenase, and phytase enzymes, whereas both conventional PS and PE-MPs decreased their activities. Moreover, As and PLA-MPs combined stress altered soil bacterial communities by increasing the relative abundance of Protobacteria, Acidobacteria, Chloroflexi, and Firmicutes phyla by 49 %, 29 %, 82 %, and 57 %, respectively. This study provides new insights into MPs-As interactions in soil-plant system and ecological risks associated with their coexistence.

Construction of a hydrophobicity, phosphorus‐ and nitrogen‐containing layered double hydroxides‐based synergistic effect flame retardant for poly (lactic acid)

AbstractIn this work, a synergistic effect strategy was explored for fabricating hydrophobicity, phosphorus‐ and nitrogen‐containing layered double hydroxides nanosheets (LDHs) based flame retardant (LDHs‐K@DM). This fabricating process was achieved by amination of the surface of LDHs and, subsequently, interfacial self‐assembly with high P content of diethylenetriaminpenta (methylene‐phosphonic acid) (DTPMP) and high N content of melamine (MEL). The chemical construction and thermal stabilization properties of LDHs‐K@DM were confirmed via different characterization approaches. The results revealed that LDHs‐K@DM was successfully prepared and the surface of LDHs‐K@DM was transformed into hydrophobicity with high water contact angle. Moreover, LDHs‐K@DM had better thermal stability. After that, LDHs‐K@DM was molten compounded with biobased polylactic acid (PLA). It was suggested that LDHs‐K@DM were uniformly dispersed in the PLA matrix and could accelerate the decomposition of PLA to form char residues. Most importantly, the addition of 20 wt% LDHs‐K@DM into PLA can endow the composite to achieve a desirable UL‐94 V‐0 rating and the limiting oxygen index value of 30.9%. Finally, the synergistic effect flame retardant mechanism of LDHs‐K@DM was comprehensively analyzed. This synergistic decorating strategy for preparing LDHs‐K@DM flame retardant is promising for industrial production.

Fused Filament Fabrication 3D Printing Parameters Affecting the Translucency of Polylactic Acid Parts.

The effect of 3D printing parameters by Fused Filament Fabrication (FFF) on the translucency of polylactic acid (PLA) parts was investigated. Six different printing parameters were studied: object orientation, layer height, nozzle temperature, fan speed, extrusion multiplier, and printing speed. The commercially available Plasty Mladeč PLA filament and the Original Prusa MK4 3D printer were used for the experiments. The translucency of the printed samples of 50 × 25 × 1 mm dimensions was measured using a luxmeter in an integrating sphere. A total of 32 sample combinations were created. Each sample was printed ten times. The results show that all investigated parameters significantly affect the optical properties of PLA parts. The best measured translucency values were obtained when printing in portrait mode, with a layer height of 0.30 mm, nozzle temperature of 240 °C, fan speed of 100%, 0.75 set extrusion multiplier, and a speed of 40 mm/s. ANOVA was used to statistically evaluate the effect of each parameter on translucency, and statistically significant differences were found between different combinations of parameters (p < 0.05). Scanning Electron Microscope (SEM) analysis provided detailed images of the surface structure of the printed samples, allowing for a better discussion of the microscopic properties affecting the translucency. The best print setting has an efficiency of 88% compared to the default setting of 65%. The ability of visible light to pass through the print (translucency) improved by 23%.

Characterization of PLA/LW-PLA Composite Materials Manufactured by Dual-Nozzle FDM 3D-Printing Processes.

This study investigates the properties of 3D-printed composite structures made from polylactic acid (PLA) and lightweight-polylactic acid (LW-PLA) filaments using dual-nozzle fused-deposition modeling (FDM) 3D printing. Composite structures were modeled by creating three types of cubes: (i) ST4-built with a total of four alternating layers of the two filaments in the z-axis, (ii) ST8-eight alternating layers of the two filaments, and (iii) CH4-a checkered pattern with four alternating divisions along the x, y, and z axes. Each composite structure was analyzed for printing time and weight, morphology, and compressive properties under varying nozzle temperatures and infill densities. Results indicated that higher nozzle temperatures (230 °C and 240 °C) activate foaming, particularly in ST4 and ST8 at 100% infill density. These structures were 103.5% larger on one side than the modeled dimensions and up to 9.25% lighter. The 100% infill density of ST4-Com-PLA/LW-PLA-240 improved toughness by 246.5% due to better pore compression. The ST4 and ST8 cubes exhibited decreased stiffness with increasing temperatures, while CH4 maintained consistent compressive properties across different conditions. This study confirmed that the characteristics of LW-PLA become more pronounced as the material is printed continuously, with ST4 showing the strongest effect, followed by ST8 and CH4. It highlights the importance of adjusting nozzle temperature and infill density to control foaming, density, and mechanical properties. Overall optimal conditions are 230 °C and 50% infill density, which provide a balance of strength and toughness for applications.

Effect of carbodiimides on the compatibility and hydrolytic behavior of PLA/PBAT blends

Blends of polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) have great potential to replace conventional polyolefin and polyester materials. However, poor compatibility and fast degradation rate limit its development. In this paper, the effects of two monomer-type carbodiimides and one polymerized carbodiimide on the crystalline, thermal stability, hydrolysis properties, and mechanical properties of PLA/PBAT blends are investigated by Fourier transform infrared spectroscopy, scanning electron microscope, differential scanning calorimetry, thermogravimetric analysis, gel permeation chromatography, melt mass-flow rate, terminal carboxyl content, tensile properties, and rotational torque. It is found that all the three carbodiimide additives can improve the compatibility and enhance the mechanical, processing, and thermal stability properties of PLA/PBAT blends except for their reduced crystallization performance. Moreover, regarding the hydrolysis properties, the two monomeric carbodiimides exhibit little effect on the hydrolysis of PLA/PBAT blends, even accelerating the degradation rate under alkaline conditions. However, the antihydrolysis effect of polycarbodiimide is remarkable, which effectively improves the compatibility and antihydrolysis properties of PLA/PBAT blends.

Mechanical and shape-memory properties of TPMS with hybrid configurations and materials

ABSTRACT Triply periodic minimal surface (TPMS) structures with excellent properties of stable energy absorption, light weight, and high specific strength could potentially spark immense interest for novel and programmable functions by combining smart materials, e.g. shape memory polymers (SMPs). This work proposes TPMS lattices with hybrid configurations and materials that are composed of viscoelastic and shape-memory materials with the aim to bring temperature-dependent mechanical properties and additional dissipation mechanisms. Different configurations and diverse materials of polylactic acid (PLA), fiber-reinforced PLA, and polydimethylsiloxane (PDMS) are induced, generating five types of TPMS lattices, including (Schoen’s I-WP) IWP uniform lattice, IWP lattice with density gradient, hybrid configurations, hybrid materials, and filled PDMS, which are fabricated by 3D printing. The fracture morphologies and the distribution of carbon fibers are demonstrated via scanning electron microscopy with a focus on the influence of carbon fiber on shape-memory and mechanical properties. Shape recovery tests are conducted, which proves good shape memory properties and reusable capability of TPMS lattice. The combined methods of experiments and numerical simulation are adopted to evaluate mechanical properties, which presents multi-stage energy absorption ability and tunable vibration isolation performances associated with temperature and hybridization designs. This work can promote extensive research and provide substantial opportunities for TPMS lattices in the development of functional applications.

Comparative Study of Polycaprolactone and Polylactic Acid as Matrices for Atorvastatin Release - Biomaterial Suppliers for Additive Manufacturing in Drug Delivery Systems using nanocomposites

The use of the polymer/drug combination in additive manufacturing involves filament production through hot melt extrusion (HME). Atorvastatin (ATV) has diverse effects, including bone anabolism and cardiovascular improvements. This study compares the addition of ATV to polycaprolactone (PCL) and polylactic acid (PLA). Filaments of PCL/ATV and PLA/ATV were produced through HME and characterized by Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Raman, Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), and Small-Angle X-ray Scattering (SAXS). ATV release was assessed using UV-Vis. The EDS analysis confirmed the presence of ATV in the filament, despite it not being possible, based on surface morphology, to distinguish between polymer and drug, which indicates good dispersion of ATV in the polymeric matrix. FTIR, RAMAN, XRD, and SAXS analyses reveal ATV's distinct interactions with PLA and PCL. FTIR highlights ATV's stronger interaction with PLA, while Raman indicates changes in PLA, they are less pronounced than in PCL. The XRD shows PLA's amorphous nature compared to PCL semi crystallinity nature. XRD suggests potential ATV amorphization in PLA_ATVf (filaments), while PCL_ATVf shows a decrease in crystallinity compared to PCL. HME's effect on ATV is essential. Despite ATV's crystallinity in PCL-ATVf by XRD, its release resembles PLA_ATVf. At the eighth hour, ATV release from PCL_ATVf was 12% higher than from PLA_ATVf. The data fitted the Korsmeyer-Peppas model.

Novel post-heat treatment green biodegradable PLA@SiO2 nanocomposite membrane for water desalination

Membrane distillation (MD) has received significant attention because of its energy efficiency and ability to treat industrial wastewater and salty water. However, the synthetic nature of commonly used membranes raises environmental disposal concerns, requiring the development of alternative eco-membranes. To address this issue, a novel, eco-friendly membrane using polylactic acid (PLA) coated with green silica nanoparticles (SiO2 NPs), modified by post-heat treatment, was developed for effective direct contact membrane distillation (DCMD). Herein, two nanofibrous membranes were fabricated via electrospinning/electrospraying: one, PLA, with a 12.5 wt% PLA solution, and another, PLA@SiO2, with 2 % (w/v) SiO2 NPs coating. The PLA@SiO2 membrane demonstrated enhanced hydrophobicity. Various post-heat treatments were applied to optimize membrane properties, such as structure, pore size, hydrophobicity, liquid entry pressure (LEP), thickness, and thermal stability. In addition, the desalination performance of all membranes was evaluated using a DCMD unit for 6 h. Results showed that the heat-pressed then annealed PLA@SiO2 membrane (denoted M44) exhibited notable improvements, including an LEP of 128.7 kPa, a tunable pore size of 0.21 μm, and a contact angle of 135.9°. Furthermore, the M44 membrane demonstrated a porosity of 80.5 %, a stable permeate flux of 14.3 kg.m−2.h−1, and an exceptional salt rejection of 99.99 % over a 24 h DCMD test. This novel eco-membrane shows promising potential for efficient desalination and represents a significant advancement in sustainable MD applications.

Degradation of thermoplastic polymers for fused filament fabrication under (S)TEM electron beam irradiation

The structural characterization of polymers and, in particular, of those used in Additive Manufacturing (AM) technologies, is essential to improve the understanding of their structure-property relationship for promising high-performance applications. For this, (scanning) transmission electron microscopy-electron energy loss spectroscopy, (S)TEM-EELS is an outstanding tool for exploring materials chemical and structural characteristics at high spatial resolution. However, the high beam-sensitivity of soft materials, such as polymers, hinders the possibility of probing in-depth analysis provided by (S)TEM-EELS. In this work, we analyse the electron beam irradiation damage of four polymers commonly used in Fused Filament Fabrication (FFF), namely polylactic acid (PLA), polycaprolactone (PCL), acrylonitrile butadiene styrene (ABS) and acrylonitrile styrene acrylate (ASA). For this, sequential low-loss and core-loss EEL spectra have been recorded, and the related signals have been monitored as a function of the accumulated dose. Our results show that the critical electron doses using the specimen thickness variations are larger for polymers containing aromatic groups (ABS and ASA) than for aliphatic polymers (PLA and PCL). Regarding the different elements, a larger sensitivity to the electron beam of oxygen regarding carbon and nitrogen is also evidenced. Our results have shown that polymer degradation occurs to a larger extent in the initial steps of electron irradiation, for very low accumulated electron doses, meaning that care should be taken in the selection of the microscopy settings to avoid artefacts produced by the electron beam. Degradation pathways for the four polymers studied are discussed.

Genome-Centric Metagenomics Insights into the Plastisphere-Driven Natural Degradation Characteristics and Mechanism of Biodegradable Plastics in Aquatic Environments.

Biodegradable plastics (BPs) are pervasively available as alternatives to traditional plastics, but their natural degradation characteristics and microbial-driven degradation mechanisms are poorly understood, especially in aquatic environments, the primary sink of plastic debris. Herein, the three-month dynamic degradation process of BPs (the copolymer of poly(butylene adipate-co-terephthalate) and polylactic acid (PLA) (PBAT/PLA) and single PLA) in a natural aquatic environment was investigated, with nonbiodegradable plastics polyvinyl chloride, polypropylene, and polystyrene as controls. PBAT/PLA showed the weight loss of 47.4% at 50 days and severe fragmentation within two months, but no significant decay for other plastics. The significant increase in the specific surface area and roughness and the weakening of hydrophobicity within the first month promoted microbial attachment to the PBAT/PLA surface. Then, a complete microbial succession occurred, including biofilm formation, maturation, and dispersion. Metagenomic analysis indicated that plastispheres selectively enriched degraders. Based on the functional genes involved in BPs degradation, a total of 16 high-quality metagenome-assembled genomes of degraders (mainly Burkholderiaceae) were recovered from the PBAT/PLA plastisphere. These microbes showed the greatest degrading potential at the biofilm maturation stage and executed the functions by PLA_depolymerase, polyesterase, hydrolase, and esterase. These findings will enhance understanding of BPs' environmental behavior and microbial roles on plastic degradation.

Abiotic degradation and accelerated ageing of microplastics from biodegradable and recycled materials in artificial seawater

Microplastics (MPs) are considered one of the most widespread pollutants in all ecosystems worldwide. In the environment, MPs can undergo hydrolysis and/or oxidation, resulting in the release of low-molecular weight degradation products, along with additives, and adsorbed organic pollutants. In this study, the morphological, chemical, and thermal changes of microplastics obtained from two biodegradable plastics, polylactic acid and Mater-Bi®, and a recycled plastic, recycled-polyethylene terephthalate, were examined after accelerated ageing under photo-oxidative conditions in synthetic seawater in a Solarbox system, and after thermal treatment in the dark. Thermal properties were studied by thermogravimetric analysis, differential scanning calorimetry, and evolved gas analysis-mass spectrometry. Compositions and changes of chemical components of the polymers were evaluated by attenuated total reflection-Fourier transform infrared spectroscopy and pyrolysis-gas chromatography–mass spectrometry. The leachable fractions and degradation products released in synthetic seawater by degraded MPs were characterized by gas chromatography–mass spectrometry. This study allowed us to identify hydrolysis as the main degradation pathway of the polymers under analysis, and to characterize not only the oligomers and degradation products released in the water as a consequence of degradation, but also additives used in plastic item formulations. This study improves our understanding of these polymers' behavior under accelerated ageing conditions.

Optimizing the grasping behavior of a soft robot's gripper

AbstractIn this study, smart composite materials based on 4D printing technology were used to determine the grasping ability of four‐claw gripper of soft robot. First, fused deposition modeling (FDM) is used to prepare polylactic acid (PLA) strips on the surface of a rectangular bamboo substrate to create a single‐claw gripper for a smart composite soft robot, while using stimulus (heat) to deform and recover its original shape. Here, the authors first evaluate the deformation and recovery angle of the single‐claw gripper of the smart composite soft robot, as well as various processing parameters such as heating temperature and time. This study then used FDM to print PLA ribbons on cross‐shaped bamboo sheets to design the four‐claw gripper of soft robot and its gripper technology was actuation type. Then, the four‐claw gripper of soft robot was used to grab the table tennis ball to test its grasping ability. Finally, four processing parameters (width of claw, pitch of PLA ribbon, heating temperature, and heating time) were applied to determine the grasping ability of the four‐claw gripper of soft robot. The optimal processing parameters for the grasping ability of the four‐claw gripper of soft robot were width of claw of 20.2 mm, pitch of PLA ribbon of 1 mm, heating temperature of 200°C, and the heating time of 15 s. The authors also applied the operation window of two processing parameters to discuss the success of the grasping ability of the four‐claw gripper of soft robot. The innovation of this study is the use of PLA/bamboo composite materials as the four‐claw gripper of soft robot and these materials are cheap, easy to obtain, and can be recycled naturally. This study uses a simple thermal stimulus to enable the four‐claw gripper of soft robot to easily grasp irregular objects.Highlights The innovative composite material of polylactic acid and bamboo fabricated by 3D printing. Width of claw and heating temperature are the key factors on grasping ability. Operating window of grasping ability appears on four‐claw gripper of soft robot.

Analysis of emission of volatile organic compounds and thermal degradation in investment casting using fused deposition modeling (FDM) and three-dimensional printing (3DP) made of various thermoplastic polymers.

The study examined the degradation process of various types of polymers used to form models using the fused deposition modeling (FDM) and three-dimensional printing (3DP) methods and used in the investment casting method. Commercial filaments made of polylactide (PLA), acrylonitrile butadiene styrene terpolymer (ABS), high-impact polystyrene (HIPS), polyamide 12 (PA12), poly(methyl methacrylate) (PMMA), and polypropylene (PP) were used to produce gypsum molds. The assessment included organic volatile compounds (VOCs) released during mold heating and model degradation, which is characteristic of this technological process. The screening qualitative chromatographic analysis of decomposition products sampled from various points of the production hall made it possible to define potential threats related to the processing of selected polymers and the necessary preventive measures. Furthermore, passive diffusion-type samplers were used at the sampling stage of VOCs emitted to the gaseous phase to reduce nuisance and user interference. Studies have been completed to characterize the thermoplastic polymer degradation process. The coupled thermogravimetry (TGA) with analysis of gaseous products by infrared spectroscopy with Fourier transformation (FT-IR) has been used. The presented results are the first to compare and rate the use of this still-developing novel aspect of castings by the method of fused models.

Improving poly(lactic acid) fire performances via blending with benzoxazine

Improving the mechanical performance of PLA via reactive blending with thermosets is an interesting approach, however, not well explored for its fire performance improvement. With our approach, the fire performances of PLA were improved by blending PLA with a commercially available bisphenol-F-based benzoxazine. To establish the proof of concept, the benzoxazine was initially pre-cured at either 100 °C or 150 °C for a pre-selected time i.e. 60′, 80′, or 120′. The benzoxazine samples were then blended with PLA matrix via an extrusion process at 10 wt.% or 20 wt.% loadings. Detailed thermal and chemical investigations via Differential Scanning Calorimetry (DSC) and Size Exclusion Chromatography (SEC), and the evaluation of the mechanical properties, confirmed that the addition of benzoxazine does not influence the intrinsic properties of PLA. The fire performance was tested by Mass Loss Cone (MLC) calorimetry. PLA formulation with 20 wt.% of the benzoxazine cured 80′ at 150 °C, lead to a 43 % reduction of the peak of heat release rate compared to neat PLA. This was attributed to increased char formation during the combustion process. Also, the char formation permits a significant delay in the temperature increase of the sample.

Asymmetric sandwich poly(lactic acid) composite films fabricated by one-step phase separation approach towards absorption-dominant electromagnetic interference shielding and hydrophobicity

The absorption-dominant electromagnetic interference (EMI) shielding polymer composites with excellent hydrophobicity and environmental friendliness are highly demanded to alleviate secondary electromagnetic radiation in high-humidity surroundings. Herein, cobalt–nickel@carbon nanotubes-polylactic acid-silver nanowires (CoNi@CNTs-PLA-AgNWs) films with asymmetrical sandwich architectures were successfully fabricated via a one-step magnetic field-assisted non-solvent-induced phase separation methodology. AgNWs are mainly spread on the rough top layer, but CoNi@CNTs are primarily distributed in the porous bottom layer of CoNi@CNTs-PLA-AgNWs composite films. Owing to the unique asymmetrical magnetic-electric dual networks, 150CoNi@CNTs-PLA-7AgNWs film displays the fantastic averaged EMI SET of 53.7 dB and optimal A of 0.61, illuminating the dominance of absorption in EMI shielding and efficiently alleviating the secondary electromagnetic pollution. In order to enhance the stability of EMI shielding in damp environment, CoNi@CNTs-PLA-AgNWs composite films are dip-coated in 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FDTS) solution for hydrophobic modification. The excellent water repellency is achieved on both top and bottom surface of CoNi@CNTs-PLA-AgNWs films with WCA > 150° and > 120°, respectively, while maintaining the superior EMI shielding performance. Such facile one-step asymmetrical sandwich structure design strategy provides valuable insight into preparing and controlling hydrophobic absorption-dominant EMI shielding composites, which is anticipated to have numerous implications for smart and portable electronic devices in high-humidity environment.

A novel poly(Rhodamine B) coated polylactic acid doped carbon black electrode for nitrite detection in drinking water

A novel poly(Rhodamine B) coated polylactic acid doped carbon black electrode for nitrite detection in drinking water

Exploring the constituents and thermal characteristics of miscanthus floridulus for biomass composites

Miscanthus floridulus (MF) possesses notable attributes including high photosynthetic efficiency, rapid growth, robust adaptability, and substantial biomass yield. It is widely researched in fields such as genetics, special materials, bioenergy, and ecological protection. However, the research on the addition of MF for biomass composites remains limited due to the absence of comprehensive analysis concerning the composition, internal molecular structure, and properties of MF. A thorough exploration of the fundamental properties of MF has the potential to broaden their advantages and facilitate the advancement of biomass. This investigation delves into the structural characterization and properties of MF, focusing on its stems, leaves, and tassels. Firstly, the primary constituents of MF comprise cellulose, hemicellulose, and lignin. Cellulose predominates in the stem, exhibiting the highest crystallinity, while lignin content peaks in the tassel with the lowest crystallinity. The leaf falls between these extremes in terms of crystallinity. Secondly, carbon and oxygen elements constitute over 95 % of MF's primary components, alongside trace elements like phosphorus and sulfur. Additionally, chemical structure of MF features abundant characteristic functional groups such as hydroxyl, carbonyl, and benzene rings. Studies indicate that samples with low hemicellulose and high lignin content demonstrate superior thermal stability. Consequently, the stem of MF exhibits optimal low-temperature thermal stability, while the tassel excels in high-temperature conditions. Finally, the data highlights a significant influence in the mechanical properties of polylactic acid materials upon the addition of MF. With a 5 % addition of MF, the tensile modulus and flexural strength of the PLA composite reached their optimal values of 933.91 MPa and 55.28±8.77 MPa, respectively. This research establishes a theoretical groundwork for integrating MF into biomass composite materials.

Toughening Polylactic Acid with Epoxidized Natural Rubber via Altering the Dicumyl Peroxide Mixing Sequence

Toughening Polylactic Acid with Epoxidized Natural Rubber via Altering the Dicumyl Peroxide Mixing Sequence

The degradation of polylactic acid face mask components in different environments

The disposal of fossil fuel-based plastics poses a huge environmental challenge, leading to increased interest in biodegradable alternatives such as polylactic acid (PLA). This study focuses on the environmental impact and degradation of PLA face mask components under various conditions (UV (Ultraviolet) radiation, DI water, landfill leachate of various ages, seawater, and enzyme). Under UV exposure, notable changes in physicochemical properties were observed in the PLA masks, including increased oxidation over time. Degradation rates varied across environments, with old landfill leachate and enzyme degradation having a notable impact, especially on meltblown layers. Furthermore, it was found that seawater conditions hampered the degradation of PLA masks, likely due to the inhibitory effect of high salt concentrations. The pathways of chemical group changes during degradation were elucidated using 2D-COS (Two-Dimensional Correlation Spectroscopy) maps. The investigation into the release of microparticles and oligomers further revealed the degradation mechanism. Moreover, PLA masks were found to release fewer microparticles when degraded in studied environments when compared to traditional polypropylene masks. Furthermore, correlation analysis highlighted the influence of factors such as carbonyl index and contact angle on degradation rates, underscoring the complex interplay between environmental conditions and PLA degradation. This comprehensive investigation advances the understanding of PLA degradation pathways, which are crucial for mitigating plastic pollution and promoting the development of sustainable products.

Antifungal activity of poly(lactic acid) nanofibers containing the essential oil from Corymbia citriodora Hook or the monoterpenes β-citronellol and citronellal against mycotoxigenic fungi.

Food contamination by mycotoxigenic fungi is one of the principal factors that cause food loss and economic losses in the food industry. The objective of this work was to incorporate the essential oil from Corymbia citriodora Hook and its constituents citronellal and β-citronellol into poly(lactic acid) nanofibers; to characterize the nanofibers by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC); to evaluate the antifungal activity by the fumigation method; to evaluate the antimycotoxigenic activity against Aspergillus carbonarius, Aspergillus ochraceus, Aspergillus westerdijkiae, Aspergillus flavus and Aspergillus parasiticus; and to evaluate the morphology of these microorganisms. All the nanofibers had a regular, smooth and continuous morphology. FTIR analyses confirmed that the active ingredients were incorporated into the polymer matrix. All samples exhibited antifungal and ochratoxigenic inhibitory activities of up to 100% and 99%, respectively, with the best results observed for (PLA + 30 wt% β-citronellol) nanofibers and (PLA + 30 wt% citronellal) nanofibers. However, 100% inhibition of the production of aflatoxin B1 and B2 was not observed. The images obtained by SEM indicated that the nanofibers caused damage to the hyphae, caused a decrease in the production of spores, and caused deformation, rupture and non-formation of the conid head, might be an alternative for the control of mycotoxigenic fungi.