Poly Lactic Acid Research Articles

Effect of Material Extrusion Process Parameters to Enhance Water Vapour Adsorption Capacity of PLA/Wood Composite Printed Parts

This study aims to optimise the water vapour adsorption capacity of polylactic acid (PLA) and wood composite materials for application in dehumidification systems through material extrusion additive manufacturing. By analysing key process parameters, including nozzle diameter, layer height, and temperature, the research evaluates their impact on the porosity and adsorption performance of the composite. Additionally, the influence of different infill densities on moisture absorption is investigated. The results show that increasing wood content significantly enhances water vapour adsorption, with nozzle diameter and layer height identified as the most critical factors. These findings confirm that composite materials, especially those with higher wood content and optimised printing parameters, offer promising solutions for improving dehumidification efficiency. Potential applications include heating, ventilation, and air conditioning systems or environmental control. This work introduces an innovative approach to using composite materials in desiccant-based dehumidification and provides a solid foundation for future research. Further studies could focus on optimising material formulations and scaling this approach for broader industrial applications.

Effects of biological filtration by ascidians on microplastic composition in the water column

Plastic pollution, a widespread environmental challenge, significantly impacts marine ecosystems. The degradation of plastic under environmental conditions results in the generation of microplastic (MP; <5 mm) fragments, frequently ingested by marine life, including filter-feeders such as ascidians (Chordata, Ascidiacea). These organisms are integral to benthic-pelagic coupling, transporting MP from the water column through marine food web.Here, we explored the effect of filtration and digestion by the solitary ascidian Styela plicata on the composition of MP in the water column and on the sinking rates of faecal matter, focusing on differences between two distinct plastics, polystyrene (PS) and the biodegradable polylactic acid (PLA). The ascidians efficiently removed 2–5 μm particles within 2 h of filtration. Following digestion and secretion process, PS concentrations in water increased while PLA concentration remained stable. Some particles were egested into the water column repackaged inside faecal pellets, which significantly increased the pellets' drag force and sinking velocity. Raman spectral analysis of digested MP revealed distinct spectrum alterations due to coating by organic substances. These findings highlight the role of ascidians — and other filter-feeders— in modifying the structure of MP in their environment. Research into such modifications is crucial for understanding the MP cycle and its consequences in marine environments.

Improving the tensile properties of hemicellulose/polylactic acid (PLA) blends prepared by solvent casting

AbstractThe development of new biopolymers has been explored as an alternative to improve the biodegradability of conventional synthetic plastics, such as those used in the packaging industry. Hemicelluloses are biodegradable polymers extracted from plants that, when combined with other biodegradable polymers, such as polylactic acid (PLA), can be easily processed and satisfy the mechanical requirements for commercial application. Thus, this work seeks a biodegradable blend that combines hemicellulose and PLA properties using solvent casting. The influence of hemicellulose content (5, 10, 15, and 20 wt%) on the thermal and mechanical properties was studied. For that purpose, thermogravimetric analysis and differential scanning calorimetry were applied to determine the thermal stability and crystallinity of the materials. Additionally, water uptake and mechanical tests provided information regarding the mechanical and hygroscopic behavior of the blends due to hemicellulose addition. As a result, the blends presented intermediate thermal stabilities between those of hemicellulose and PLA and increased crystallinities with hemicellulose content. The blends are more flexible and hygroscopic than PLA and more resistant than pure hemicellulose. Given the biodegradable nature of PLA and hemicellulose, these blends have the potential for application in sustainable packaging.

Essai de production de l’acide polylactique (PLA) à partir de la mélasse de canne à sucre en vue d’élaborer les emballages bioplastiques

This work involves the development of a bioplastic replacement for non-degradable plastics in packaging. The objective was to produce polylactic acid (PLA) from sugarcane molasses with locally produced Lactobacillus delbrucckii. Polylactic acid is a biosourced and biodegradable polymer, it can be plasticized. The lactic acid bacteria necessary for the synthesis were isolated and identified as Lactobacillus delbrucckii following their characteristics. The sugar cane molasses used came from the KwiluNgongo sugar mill with a concentration of 410.9 g/L of fermentable sugar. 1L of diluted molasses was fermented with the inoculum of Lactobacillus delbrucckii in a ratio of 10/1. This fermentation produced 98 g of lactic acid after purification (63.6%). Lactic acid was polymerized to polylactic acid (92%), via lactide (78.46%), by ring opening. Lactobacillus delbrucckii colonies were characterized by Gram staining, catalase test, morphology, appearance of the colony and mode of fermentation. The Brix degree, pH, density and fermentable sugar level were determined on the molasses. The polymer obtained had a brittle behavior when heated and its mixture with 5% glycerol gelled more weakly than in the presence of 10% glycerol.

Development of Functionalized Polylactide Thin Films Using Poly(methylhydrogenosiloxane) Sol-Gel Process with Improved Antifouling Properties.

Biobased polylactide (PLA) films were modified with low reticulate polysiloxane gel acting as a scalable platform for the hydrophilization of polymeric film surface. The PLA thin film was first coated with poly(methylhydrogenosiloxane) (PMHS) by the sol-gel transition via the condensation of diethoxymethylsilane (DH) and triethoxysilane (TH) using trifluoromethanesulfonic acid as a catalyst. Then, hydrosilylation of Si-H bonds in the presence of Karstedt's catalyst allowed the covalent grafting of hydrophilic alkene-containing molecules, i.e., triethylene glycol monomethyl allyl (TEGMEA) and a new zwitterionic allylcarboxybetaine (ACB) synthesized for the first time by the quaternization of dimethyl allyl amine (DMAA) with β-propiolactone. PMHS coating on the PLA film was evidenced by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The observation by atomic force microscopy (AFM) revealed a homogeneous coating with low roughness (RMS = 0.29 nm). The hydrophilicity of functionalized PLA films was determined by water contact angle (WCA) measurements using the captive bubble method. A large increase in wettability properties was observed for both grafting with TEGMEA (WCA = 38°) and ACB (WCA = 42°) in comparison with the native PLA film (WCA = 80°). Moreover, the biocompatibility and antifouling efficiency of functionalized PLA films were evaluated by protein adsorption, bacterial adhesion, and cytotoxicity tests. The results indicate that the grafting of the two types of hydrophilic compounds does not affect the biocompatibility of PLA while significantly reducing protein adsorption and bacterial adhesion, thus showing the great potential of this surface functionalization strategy for applications in the medical field.

Compressive behavior of additively manufactured lightweight structures: Infill density optimization based on energy absorption diagrams

The use of 3D-printed components as load-bearing structures is widely studied, while their use as energy absorbers constitutes a gap in the additive manufacturing (AM) field. Most of the reported works address the compressive behavior of AM parts up to low strains (<15%), thus omitting many important properties. Therefore, this paper presents the compression characterization of Polylactic Acid (PLA) samples with different infill densities-IDs (10–100% range, with a step of 10%) fabricated by material extrusion (MEX) AM process. The physical (dimensional accuracy, printing time and sample mass) and mechanical (elastic, strength, strain and energy absorption) properties are determined and discussed in detail, along with the failure mechanisms that occur in the samples. Moreover, an ID optimization is performed based on the energy absorption diagrams (EAD), a unique approach in the AM field. The highest values of compressive strength (81 MPa) and modulus (1306.6 MPa) are found for 90%-ID, over 2.2% higher than those obtained for 100%-ID. On the other hand, based on three different approaches, EAD identified 30%-ID as optimal. The 30%-ID samples absorb the largest amount of energy (12 MJ/m3) at the lowest (ideal) peak stress value (23.57 MPa), which is 69.1% lower than that for 100%-ID. At low IDs (<30%), the samples exhibit a brittle behavior, changing to a ductile one with the increase of ID (≥40%). The MEX-printed PLA samples show a dimensional relative error below 0.15%, and the optimization process reduces the amount of filament material by 54.3% and the printing time by 42.7%.

Stereoselective Ring‐Opening Polymerization of Racemic Lactide by Racemic Organo‐Catalyst at Room Temperature: Direct Access to Stereocomplex Polylactides

AbstractThe stereoregularity of poly(lactide) (PLA) plays a significant role in its physicochemical properties. In recent years, various metallic and nonmetallic catalysts have been developed. Organic catalysts, in particular, have garnered attention due to their potential use in biomedical applications, making them safer options. This study presents the design of a cost‐effective thiourea‐based racemic organocatalyst [(rac‐TU)Me] and its effective utilization in ring‐opening polymerization (ROP) of lactide. Using the catalyst and optimized base (N,N‐dimethylcyclohexylamine), ROP in dichloromethane achieved 98% monomer conversion and controlled molecular weights in 48 h. The polylactides obtained using this catalyst exhibited moderate tacticity, with a Pm value ranging from 0.71 to 0.78. The bulk structure of synthesized poly(lactic acid) (PLAs) is extensively studied using DSC, FTIR, and WAXS. The DSC analysis indicated stereoregular PLAs synthesized from rac‐lactide exhibited a higher melting transition than isotactic PLAs. Furthermore, the FTIR and WAXS studies revealed characteristic peaks and patterns typically associated with stereocomplex PLAs. These analytical results confirm the stereocomplex bulk structures of these PLAs synthesized using this organic catalyst [(rac‐TU)Me].

Supercritical carbon dioxide foamed thermoplastic polyester elastomer with poly(lactic acid) blending: shrinkage reduction and expansion ratio improvement

Supercritical carbon dioxide foamed thermoplastic polyester elastomer with poly(lactic acid) blending: shrinkage reduction and expansion ratio improvement

High-Performance Flexible PLA/BTO-Based Pressure Sensor for Motion Monitoring and Human-Computer Interaction.

Flexible electronics show wide application prospects in electronic skin, health monitoring, and human-machine interfacing. As an essential part of flexible electronics, flexible pressure sensors have become a compelling subject of academic research. There is an urgent need to develop piezoelectric sensors with high sensitivity and stability. In this work, the high flexibility of polylactic acid (PLA) film and the excellent ferroelectric properties and high dielectric constant of tetragonal barium titanate (BTO) led to their use as filling materials to fabricate flexible piezoelectric composite films by spinning coating. PLA is used to produce flexible binding substrates, and BTO is added to the composite to enhance its electrical output by improving its piezoelectric performance. The peak output voltage of the PLA/BTO tetragonal piezoelectric film is 22.57 V, and the maximum short-circuit current was 3041 nA. Durability tests showed that during 40,000 s of continuous operation, in the range of 15~120 kPa, the linear relationship between pressure and the film was excellent, the sensitivity for the output voltage is 0.176 V/kPa, and the output current is 27.77 nA/kPa. The piezoelectric pressure sensor (PPS) also enables accurate motion detection, and the extensive capabilities of the PENG highlight its potential in advancing motion sensing and human-computer interactions.

Biomimetic toughening design of 3D-printed polymeric structures: Enhancing toughness through sacrificial bonds and hidden lengths

Spider silk is known for its excellent strength and fracture resistance properties due to its molecular design structure, characterized by sacrificial bonds and hidden lengths. These structures have inspired reinforcements of synthetic polymer materials to enhance toughness. In this study, we mimic these natural toughening mechanisms by designing and manufacturing 3D-printed polymeric structures incorporating overlapping curls consisting of coiling fiber with sacrificial bonds and hidden lengths. Utilizing the liquid rope coiling effect, we manufactured overlapping curls using three polymers: polylactic acid (PLA), liquid crystal polymer (LCP), and polyamide 6 (PA6). Uniaxial tensile tests were performed to characterize the mechanical properties of overlapping curl as a function of geometries, post-treatments, and material constitutive parameters. Our results show that single-sided overlapping curls can fully unfold while double-sided curls are prone to premature failure. Heat-pressure post-treatment was found to significantly increase the load-capacity of the sacrificial bonds by up to ▪ due to increased contact area. However, the defects introduced in the fibre after the break of the sacrificial bonds, make the structure more susceptible to premature failure, limit the complete unfolding of the hidden length, and lead to a decrease up to ▪ of the toughness. To guarantee the complete unfolding of the hidden lengths and improve the toughness, we demonstrate that selecting a polymer material with either high fracture strength (e.g., LCP, ▪) or high fracture strain (e.g., PA6, >2) is crucial, and increase toughness up to ▪ and ▪, respectively.

Infiltration of glass nanofiber-reinforced polylactic acid into delignified hardwood toward photoluminescent and mechanically reliable smart windows

Ultraviolet-protective, mechanically reliable, and photoresponsive wood that can switch color under ultraviolet light was developed. A combination of alkaline earth-doped strontium aluminate (ASA) as a photoluminescent pigment and glass nanofiber-supported polylactic acid as a hosting agent was infused into a delignified wood, producing transparent wood with photochromic activity. The ASA phosphor has proven high thermal stability and photostability. A typical process for producing colorless photoluminescent wood includes the well-dispersion of ASA in glass nanofiber-supported polylactic acid without agglomeration. As proven by the coloration measurements, the current photoluminescent wood becomes green under ultraviolet light and remains transparent under daylight. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) were employed to determine the morphology of the phosphor particles and glass fibers, demonstrating sizes of 12–21 nm and 50–125 nm, respectively. The luminescent wooden samples were studied by numerous microscopic and spectroscopic techniques, including SEM, X-ray fluorescence (XRF), and energy-dispersive X-ray (EDX). Upon excitation at 365 nm, the luminescence wood demonstrated an emission peak at 518 nm. When increasing the ASA concentration, the photoluminescent hardwoods displayed improved ultraviolet protection and better water resistance. The responsiveness of the luminescent wood to UV irradiation was fast and reversible.

Effect of thermal shocks on the interfacial bond strength of sandwich composites built with rigid and soft materials produced through extrusion process

The mechanical behavior and adhesion strength of the sandwich composite, which consists of a flexible and a rigid material, were examined using extruded polylactic acid (PLA) and thermoplastic polyurethane (TPU). Three types of binders were combined with the appropriate hardeners to bond the extruded materials. The fabricated specimens are subjected to a different number of thermal shock cycles, with a maximum and minimum temperature of 80 °C and −18 °C, respectively. The sandwich composite's mechanical properties, including tensile, flexural, and impact strength, were assessed after 20, 40, and 80 cycles of thermal shock. The results indicated that the ductility of PLA material was significantly impacted by the thermal shock cycles. After completing the maximal thermal shock cycles, the composites joined with polyester resin exhibited a lower strength reduction in the impact specimens. Maximum tensile strength of 22.3 MPa, flexural strength of 31.6 MPa, and impact strength of 8.3 J were recorded prior to the application of thermal shocks to the specimens. The specimens that were bonded with epoxy resin recorded the maximal tensile, flexural, and impact strength. Following the thermal shock cycles, the composites bonded with epoxy resin exhibited a lesser reduction in tensile and flexural strength, while the composites bonded with polyester resin showed a lower strength reduction for impact specimens. The tensile and flexural specimens encountered a 7.54 % and 20.24 % reduction in strength, respectively, after undergoing 80 cycles of thermal shocks. The impact specimens experienced an 8.62 % reduction in strength.

Hydrogen Peroxide-Induced Controlled Degradation of Poly(lactic acid) for Melt-Blown Nonwovens

Hydrogen Peroxide-Induced Controlled Degradation of Poly(lactic acid) for Melt-Blown Nonwovens

Augmented barrier properties of poly (lactic acid) composite packaging film reinforced by antibacterial hybrid bio‐filler: Extending the shelf life of fruits

AbstractThis work investigates the construction of biodegradable packaging film based on polylactic acid (PLA) reinforced with a novel antibacterial hybrid nanofiller to improve barrier and mechanical properties. The study focuses on incorporating silver‐ingrained silica particles (Ag–In–Si) into PLA matrix to prepare the packaging film (Ag–In–SiPLA) that has superior antibacterial, and barrier property with negligible oxygen and water vapour penetration. The Ag was synthesized using natural neem leaf extract as a reducing agent. To ingrain silver over rice husk silica (Si) an in situ technique was adopted. Hence called Ag‐In‐Si bio‐filler. The Ag–In–SiPLA films were fabricated using melt blending and sheet extrusion methods by means of a micro‐compounder. The addition of rice husk silica served the purpose of cost‐effectiveness of the packaging film along with the enhancement of the oxygen and water barrier properties of the films. The optimized sample (PLA loaded with 3% Ag–In–Si), exhibited optimum transparency, moisture resistance, and barrier properties compared with control PLA film. The experiments on Muntingia calabura (Jamaica cherry) preservation have verified the remarkable effectiveness of Ag–In–SiPLA films in preserving their quality for an extended period. These biodegradable packaging films, composed of food‐grade materials and sustainable ingredients, have the potential to provide a compostable and environmentally friendly solution for various packaging applications. This research shed light on the antibacterial Ag–In–SiPLA film as a long‐term, high‐performance fruit packaging solution.Highlights Novel antibacterial PLA composite with enhanced barrier and mechanical properties. Silver‐ingrained silica particles improve antibacterial and barrier properties. Green synthesis of silver using neem leaf extract Melt blending and sheet extrusion used to create cost‐effective packaging films. Ag–In–SiPLA films extend Muntingia calabura preservation, proving effective.

Fatigue Analysis of Polylactide Manufactured by Fused Deposition Method of 3D Printing

Nowadays, 3D printing technology has gained popularity in various industrial sectors, especially in the field of developing new products. This technology allows for the layer-by-layer construction of 3D prototypes. This research primarily focuses on the fatigue performance of 3D-printed components made of Polylactide (PLA). PLA is a versatile material and has a diverse range of applications in packaging, medical, household items, etc. The specimens were made following the ASTM D638 standard using the Fused Deposition Modeling (FDM) technique. A fatigue test was carried out to investigate fatigue performance by fluctuating the loads and speed of the rotating beam fatigue tester. The finding reveals that materials break under variable strains at a stress magnitude is less than the material's ultimate tensile strength. Furthermore, it was discovered that the degree of the stress triggering fatigue failure reduces as the number of stress cycles increases. Fatigue failure is characterized as a time-delayed fracture due to cyclic stress. The finding reveals that PLA has a low fatigue strength of 19.62N.

Mechanically Robust and Biodegradable Electrospun Membranes Made from Bioderived Thermoplastic Polyurethane and Polylactic Acid.

Petroleum-based plastic waste plagues the natural environment, but plastics solve many high-performance solutions across industries. For example, porous polymer membranes are used for air filtration, advanced textiles, energy, and biomedical applications. Sustainable and biodegradable Bioplastic membranes can compete with nonrenewable materials in strength, durability, and functionality but biodegrade under select conditions after disposal. Membranes electrospun using a blend of bioderived thermoplastic polyurethane (TPU) and polylactic acid (PLA) perform effectively under tensile and cyclic loading, act adequately as an air filter media, and biodegrade in a home-compost environment, with the aliphatic formulation of TPU showing greater biodegradability compared to the formulation containing aromatic moieties. Blending TPU with PLA dramatically increases the strain at break of the PLA membrane, while the addition of PLA in TPU stiffens the material considerably. Measurements of the pressure drop and filtration efficiency deem this electrospun membrane an effective air filter. This membrane provides a solution to the need for quality air filtration while decreasing the dependence on petroleum feedstocks and addressing the issue of plastic disposal through biodegradation.

Polylactide-Based Polymer Composites with Rice Husk Filler

In this work, composites made of polylactide (PLA) and filled with alkali-pretreated rice husk (RH) were investigated. Composites containing 20, 30, and 40 wt.% of RH were synthesized. It was shown that alkaline treatment, along with the change in crystal lattice, led to an increase in the content of non-crystalline parts and the volume of intercrystalline spaces, and the internal surface of the cellulose fiber increased, which resulted in improved adhesion of the fiber with the matrix. The addition of rice husk to the PLA matrix led to an increase in the flexural modulus, which increased to 2881 MPa for the PLA/RH (80/20 wt.%) and 3034 MPa for the PLA/RH (70/30 wt.%) composites and lowered the peak load stress by approximately 43% for the composite with 20 wt.% RH and 56% for the composite with 30 wt.% RH. The reduction in the degree of PLA crystallinity allows macromolecules to move more freely in amorphous regions, which has a positive effect on increasing the flexibility of materials in general. The optimal formulation is a composite consisting of 30% RH and 70% PLA matrix.

Preparation and adsorption application of PLA/GO/PDA nanofiber membrane

Abstract In this study, PLA(polylactic acid)/GO(graphene oxide)/DA(Dopamine) porous nanofiber membrane was prepared by electrospinning. L16(43) orthogonal experiment was designed to investigate the effects of reaction temperature, reaction time, and DA concentration on the adsorption performance of DA oxidized and self-polymerized on the fiber. Based on the characterization of scanning electron microscopy and the determination of the adsorption performance of the fiber membrane to MB(methylene blue dye), data visualization analysis, variance analysis, and F-test were conducted to determine the optimal process parameters: reaction temperature of 45 ℃, reaction time of 30 h, and DA concentration of 2 mg/ml. PLA/GO/PDA(Polydopamine) nanofiber was prepared and characterized under the optimal process parameters. The results showed that the average diameter of the PDA-loaded nanofiber increased from 737 nm to 996 nm, and a layer of PDA with a thickness of about 129 nm was loaded on the outer surface of the fiber, making the contact angle of the fiber membrane with 0° and becoming a hydrophilic material. In adsorption performance testing of MB, the PLA/GO/PDA nanofiber membrane prepared based on the PLA/GO/DA fiber membrane with an adsorption rate of 98.81 % in 24 h was superior to the PLA/GO/PDA nanofiber membrane prepared based on the PLA/GO fiber membrane.

Boosting the Strength and Toughness of Polymer Blends via Ligand-Modulated MOFs.

Mechanically robust and tough polymeric materials are in high demand for applications ranging from flexible electronics to aerospace. However, achieving both high toughness and strength in polymers remains a significant challenge due to their inherently contradictory nature. Here, a universal strategy for enhancing the toughness and strength of polymer blends using ligand-modulated metal-organic framework (MOF) nanoparticles is presented, which are engineered to have adjustable hydrophilicity and lipophilicity by varying the types and ratios of ligands. Molecular dynamics (MD) simulations demonstrate that these nanoparticles can effectively regulate the interfaces between chemically distinct polymers based on their amphiphilicity. Remarkably, a mere 0.1wt.% of MOF nanoparticles with optimized amphiphilicity (ML-MOF(5:5)) delivered ≈3.4- and ≈34.1-fold increase in strength and toughness of poly (lactic acid) (PLA)/poly (butylene succinate) (PBS) blend, respectively. Moreover, these amphiphilicity-tailorable MOF nanoparticles universally enhance the mechanical properties of various polymer blends, such as polypropylene (PP)/polyethylene (PE), PP/polystyrene (PS), PLA/poly (butylene adipate-co-terephthalate) (PBAT), and PLA/polycaprolactone (PCL)/PBS. This simple universal method offers significant potential for strengthening and toughening various polymer blends.

Microbial Enzymes for the Biodegradation of Polylactic Acid (PLA): Molecular Docking Simulation and Biodegradation Pathway Proposal

Polylactic acid (PLA), as a biodegradable polymer, finds widespread utility across diverse sectors, encompassing transportation, agriculture, biomedicine, textiles, electronics, and food packaging. Nonetheless, its degradation kinetics exhibit significant environmental sensitivity, necessitating the development of novel biotechnological methodologies to investigate the microbial and enzymatic constituents implicated in PLA biodegradation. In this review, molecular docking simulations are discussed to analyze the enzymatic degradation of PLA using specific enzymes: proteinase K, PLA depolymerase, and lipase. The binding energy, binding affinity, and dimensions of PLA-binding sites within the enzyme cavities have been examined for each enzyme. The binding amino acid residues mainly include serine, histidine, and aspartate for all plastics, while the interactions involve Van der Waals forces, conventional hydrogen bonding, carbon-hydrogen bonding, and Pi-interactions. Based on our synthesis of the literature, a theoretical PLA biodegradation pathway that illustrates the interaction pattern between PLA and the enzymes, as well as the degradation mechanism is proposed. Our review indicates that in natural environments, enzymes work synergistically, utilizing their unique properties to facilitate an efficient sequential catalytic process for PLA degradation. This integrative approach elucidates the mechanistic underpinnings and metabolic cascades governing PLA degradation, enriching insights into enzymatic catalysis and microbial enzyme-mediated plastic biotransformation. Consequently, a comprehensive understanding of these processes is paramount in optimizing biodegradation kinetics and enhancing the environmental performance of biodegradable polymers. This review provides a detailed framework for refining PLA management strategies and advancing sustainable polymer utilization.