Polylactide Composites Research Articles

Recyclable hemp hurd fibre-reinforced PLA composites for 3D printing

In this study, 3D printing filaments were produced from hemp hurd fibre-reinforced polylactide (PLA) composites. Hemp hurd microfibres were obtained through alkaline digestion followed by a bleaching treatment and were used to produce PLA-based composites with 20–40 wt% fibre content for fused deposition modelling. Tensile testing of 3D printed composites revealed a gradual increase of Young's modulus with the addition of fibres, reaching a maximum of 7.1 GPa for the 40 wt% composite - a two-fold increase to neat PLA. However, tensile strength was only improved for the 20 wt% formulation, with an increase of 8% in comparison with neat PLA. Nevertheless, the thermo-mechanical properties of the composites were significantly enhanced with the addition of fibres. In addition, physical objects were printed from the recycled filaments to assess their recyclability and printability. It was found that the recycled filaments maintained comparable mechanical properties and printability after three recycling cycles.

Purification effect of pyrolyzed filler on the flammability of polylactide matrix

Abstract Research efforts are underway around the world to develop efficient recycling of the continuous phase of polymer composites toward reuse. It has already been demonstrated that pyrolyzed filler (PF) can be successfully used as a flame retardant for synthetic polyesters, including recycled ones. Therefore, the purpose of this work was to test the effect of PF on the flammability and thermal properties of the biopolyester phase. For this purpose, the pyrolysis technique was used, which yields a valuable solid phase in addition to the gas and liquid phases. To effectively give it a second life, a proprietary method of modifying the filler recovered by pyrolysis was developed to effectively separate and remove an organic part in the form of a layer of amorphous carbon (a-C), which acts as a universal sorbent. For this purpose, the a-C phase was extracted using binary solvent and replaced it using three types of salts: ammonium salt of benzyl phosphite, 1-butyl-3-methylimidazolium chloride (BMIC), and methyldodecylbenzyl trimethyl ammonium chloride (BMAC). Using a high-temperature processing technique, polylactide composites containing 5% (by weight) additive were obtained. The results of thermal (TGA, DSC) and flammability (PCFC, UL94, LOI) analysis studies show that the use of BMIC and BMAC salts for the intended purpose is particularly promising. The thermal stability of PLA composites containing SF-BMIC and SF-BMAC increased by 30 K and the flammability decreased by 23%. These promising results have opened up new avenues of research toward the synthesis of bio-flame retardants dedicated specifically to polylactide. Graphical abstract

Functional Silsesquioxanes-Tailoring Hydrophobicity and Anti-Ice Properties of Polylactide in 3D Printing Applications.

To explore the tailoring of hydrophobicity in 3D-printed polylactide (PLA) composites for advanced applications using additive manufacturing (AM), this study focuses on the use of Fused Deposition Modeling (FDM) 3D printing. PLA, a material derived from renewable sources, is favored for its eco-friendliness and user accessibility. Nonetheless, PLA's inherent hydrophilic properties result in moisture absorption, negatively affecting its performance. This research aims to modify PLA with organosilicon compounds to enhance its hydrophobic and anti-icing properties. Incorporating fluorinated siloxane derivatives led to significant increases in water contact angles by up to 39%, signifying successful hydrophobic modification. Mechanical testing demonstrated that the addition of organosilicon additives did not compromise the tensile strength of PLA and, in some instances, improved impact resistance, especially with the use of OSS-4OFP:2HEX:2TMOS, which resulted in an increase in the tensile strength value of 25% and increased impact strength by 20% compared to neat PLA. Differential scanning calorimetry (DSC) analysis indicated that the modified PLA exhibited reduced cold crystallization temperatures without altering the glass transition or melting temperatures. These results suggest that organosilicon-modified PLA has the potential to expand the material's application in producing moisture and ice-resistant 3D-printed prototypes for various industrial uses, thereby facilitating the creation of more durable and versatile 3D-printed components.

Resveratrol-derived halogen-free phosphate flame retardant for fire-retarding polylactide composites

Despite regarding as one of the most promising alternatives to petroleum-based plastics, polylactide (PLA) suffers from its highly flammable nature, which restricts its application range. Taking the impact on the environment into consideration, it can hold great importance to develop bio-based flame retardants for PLA. Herein, bio-derived flame-retardant resveratrol trisphosphate (RTP) is synthesized by a simple strategy without any fussy treatment. By adding only 4 wt% RTP, the PLA-4RTP composite exhibits desired flame retardancy including UL-94 V-0 rating and limiting oxygen index value of 28.6 vol%. Furthermore, PLA composites with the additive of RTP show comparable tensile strength to the pure PLA sample. RTP can inhibit the combustion process via releasing inert radical and incombustible gas to capture energetic radical and dilute combustibles.

Investigation of the Influence of UV Radiation on Compositions of Polylactide with Graphite Nanoplates

Composites of polyether polylactide (PLA) synthesized from natural raw materials with graphite nanoplates (GNP), which represent a new type of composite materials based on biodegradable polymers, were obtained by solid-phase method under the action of shear deformations. The porosity of composites was evaluated and their electrical and mechanical properties were studied. The effect of UV radiation on the molecular weight and molecular weight distribution of PLA in PLA-GNP composites of different compositions was investigated using the method of excision chromatography (EC), and the effect of the GNP nanofiller content on the change of their mechanical characteristics in the process of radiation was shown.

Enhanced photocatalytic degradation of polylactide (PLA) through TiO2-based up-conversion nanoparticles

As a degradable polymer material, the regulation of the degradation rate of polylactide (PLA) under an actual light exposure environment is of significant importance for realizing its multifaceted applications. This study aims to enhance the photodegradation of PLA under irradiation with lower-energy wavelengths by using TiO2-based up-conversion nanoparticles (UCNPs). Two modification methods were employed: doping TiO2 with Yb3+/Er3+/Tm3+ ions integrated within the TiO2 lattice, and creating a composite photocatalyst by adhering Y2O3: Yb3+/Er3+/Tm3+ to the exterior of TiO2 grains. The study investigated the impact of these two different TiO2-based UCNPs on the photocatalytic degradation rate and mechanism of PLA under simulated sunlight irradiation. Research has found that the doped TiO2, due to its narrower bandgap and higher photon utilization efficiency during the up-conversion process, exhibited superior catalytic efficiency in catalyzing the photodegradation reactions of PLA compared to unmodified TiO2 and composite TiO2. This work proposes a novel strategy for preparing PLA composites with enhanced photodegradation speed provided by modified TiO2, efficient light energy utilization offered by the up-conversion process, and potential applications in more advanced packaging and agricultural fields.

Composites of Polylactide with Carbon Nanofillers: Synthesis, Structure, Properties

Composites of Polylactide with Carbon Nanofillers: Synthesis, Structure, Properties

The Effect of Natural Plant and Animal Fibres on PLA Composites Degradation Process

One of the methods to reduce long-term excessive plastic waste is the development and use of composite materials based on biodegradable polymers and natural fibres. Composites with natural fibres can exhibit very good mechanical properties, and the presence of natural fibres can significantly accelerate the degradation of the material. This study aimed to manufacture and analyse the biodegradation process of composites based on biodegradable polylactide (PLA) filled with flax and sheep wool fibres. The effect of flax and wool fibres and their content on the degradation rate compared to that of pure PLA was investigated. The degradation progress and properties of the composites were studied using an optical microscope, SEM, measurement of surface roughness, and contact angle. Additionally, flexural strength tests, a dynamic mechanical analysis (DMA), and a thermogravimetric analysis (TGA) were conducted. The effect of natural fibres on the phase transition and degree of crystallinity was analysed using differential scanning calorimetry (DSC). The results showed that PLA degrades only under UV light, but not in the composter simulating the natural environment. However, the incorporation of both types of fibres accelerated degradation of PLA/fibres composites in soil. Flax fibre composites exhibited better mechanical properties than pure PLA. For composites with wool fibres, although they showed a significant acceleration of the degradation process in the soil, their large content in the composite caused a reduction of mechanical properties. This research showed the positive effect of the addition of natural fibres on the biodegradation of PLA.

Screw Extrusion as a Scalable Technology for Manufacturing Carbon Nanotube-Filled Polylactide Composites

Screw Extrusion as a Scalable Technology for Manufacturing Carbon Nanotube-Filled Polylactide Composites

UV-shielding, flexible and enhanced thermal-conductive polylactide composites modified with single-layered, large-sized MXene nano-sheets

UV-shielding, flexible and enhanced thermal-conductive polylactide composites modified with single-layered, large-sized MXene nano-sheets

Experimental consideration of the effects of calcium lignosulfonate and tannic acid on the flammability and thermal properties of polylactide composites

The purpose of this study was to determine the quantitative and qualitative effects of the form of natural phenolic compounds (NPCs) on the decomposition of polylactide (PLA) under different measurement conditions. For this purpose, thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), and pyrolysis-combustion flow calorimetry (PCFC) analyses were carried out not only on individual raw materials like calcium lignosulfonate (BX), tannic acid (TA), BX chemically modified with TA (BMT), but also on PLA/BX, PLA/TA, and PLA/BMT composites with 3, 6, and 9 wt.% of filler. Moreover, the work checked whether to obtain satisfactory results it is necessary to carry out chemical modification lasting many hours, or whether simple physical mixing of ingredients (TABX) is enough, e.g. in proportions 1:2, 2:4, 3:6. The results of these analyses showed that TA is neither a good flame retardant nor a highly swelling material, but when combined with BX physically or chemically, it can produce an interesting synergistic effect. This work proves that chemically obtained BMT hybrid material allows to reduce flammability by 30 % compared to PLA which cannot be achieved by physically mixing these components in a polymer melt. On the other hand, the addition of TABX is sufficient to achieve a good thermal stabilization effect under processing conditions.

Dielectric And Mechanical Properties Of PLA-Carbon Composites

This study focuses on the development and characterization of Carbon-based Polylactide (PLA) composites for 3D printer filaments. The aim is to enhance the electrical and mechanical properties of PLA by incorporating recovered carbon black (RCB) in different mesh sizes (500, 1000, 1500, and 2000 mesh). Electrical impedance spectroscopy and dielectric constant measurements were performed to investigate the electrical properties of the composites. Results showed that the addition of RCB increased the dielectric constant, with values ranging from 2.5 to 7.1, indicating improved electrical performance. Scanning electron microscopy (SEM) analysis revealed the dispersion of carbon particles within the composites, enhancing their electrical conductivity. The effect of RCB particle size on electrical properties was also explored, with smaller particle sizes (2000 mesh) resulting in the highest conductivity of 6.2 S/m. Tensile testing demonstrated that the addition of RCB increases the tensile strength of PLA, with values ranging from 28.6 MPa to 47.2 MPa, and the elastic modulus, ranging from 832 MPa to 1.56 GPa, depending on the mesh size. The optimal combination of RCB content and mesh size resulted in a composite with a tensile strength of 43.8 MPa. Overall, this research provides insights into the development of Carbon-based PLA composites with improved electrical and mechanical properties.

Properties and flame retardancy of polylactide composites incorporating tricresyl phosphate and modified microcrystalline cellulose from oil palm empty fruit bunch waste

One of the major environmental issues that have an impact on humans, animals, and their surroundings is plastic garbage. The use of biodegradable polymers in place of traditional plastics is one of the best solutions to this significant issue. The bio-circular-green (BCG) economic model is supported by the use of microcrystalline cellulose (MCC) as a bio-filler for polylactide (PLA) composites, which may also help to address the issue of improper plastic waste management. This study explores the chemical modification of MCC derived from oil palm empty fruit bunch waste (OPMC). Maleic anhydride-modified OPMC (MAMC) is successfully synthesized by a solvent-free and low temperature heating procedure. MAMC and tricresyl phosphate (TCP) were used as additives in PLA composites which were processed by melt extrusion and compression molding. Characterization studies confirmed the successful modification of MAMC and indicated that TCP played a crucial role as an effective plasticizer and flame retardant for PLA. All PLA/TCP composites showed significantly improved toughness and delayed ignition. The appropriate TCP level was 10 phr. The incorporation of TCP and MAMC resulted in a synergistic enhancement of impact strength and maintained excellent flame inhibition. Moreover, the thermal stability of the PLA composites increased with increments of MAMC.

3D-printed polylactide composites reinforced with short lyocell fibres – Enhanced mechanical properties based on bio-inspired fibre fibrillation and post-print annealing

3D-printed polylactide composites reinforced with short lyocell fibres – Enhanced mechanical properties based on bio-inspired fibre fibrillation and post-print annealing

Bio-derived phosphorous-nitrogen-silicon decorated halloysite nanotube towards enhancing flame retardant, UV-blocking and mechanical properties of poly(lactic acid)

Developing flame retardant and UV-blocking polylactide (PLA) with reinforced mechanical properties is important but challenging. Herein, bio-derived phytic acid was decorated on halloysite nanotube though silane grafting, ring-opening reaction with melamine and then electrostatic interactions with phytic acid. The obtained phopsphorous-nitrogen-silicon decorated halloysite nanotube (PNSiHNT) was incorporated into PLA to prepare PLA composites. The surface modification significantly improved the compatibility between PNSiHNT and PLA, and the flame retardant, UV-shielding and mechanical properties of the composites were enhanced. At 5% mass loading, the peak heat release and total heat release were reduced by 18% and 12% compared to pure PLA, respectively, superior to most phytic acid-based flame retardants. The relevant mechanism analysis showed that PNSiHNT can restrain the emission of combustible volatiles and promote the formation of protective char layer. Moreover, the flame-retardant PLA showed excellent UV-shielding ability with an ultraviolet protection factor (UPF) value of around 120. Due to the reinforcing effect of PNSiHNT and the strong interfacial interactions between PNSiHNT and PLA matrix, the PLA/PNSiHNT showed 77% and 116% increase in tensile strength and elongation at break compared to the bulk PLA. This study provides a strategy for designing bio-derived organic/inorganic systems for enhancing flame retardant, UV-blocking and reinforced PLA.

A molecularly engineered bioderived polyphosphonate containing Schiff base towards fire-retardant PLA with enhanced crystallinity and mechanical properties

To expand the practical application and realize sustainable development, it is urgent to develop advanced polylactide composites with fire retardancy and mechanically strong properties by utilizing bio-derived additives. Unfortunately, such desired performance portfolio is still unsatisfactory due to unclear mechanism and improper design strategy. In this paper, a novel bio-derived polyphosphonate containing Schiff base (PVP) was prepared by a two-step method of condensation and addition reactions. By incorporating only 0.5 wt% PVP, the LOI value of PLA is increased to 32.5 vol% as well as achieving a UL-94 V-0 rating. Such superior fire retardancy is ascribed to the physical barrier effect of char residue, which arising from the cyclization of Schiff base and catalytic carbonization of polyphosphonate. Due to the crosslinking reaction between PLA and PVP and nucleating effect of PVP in the PLA matrix, the mechanical strength of PLA is increased by 10.2% with addition of 1.0 wt% PVP. This study provides a feasible way for designing bio-derived fire retardants to simultaneously improving the fire retardancy and mechanical strength of PLA, thus is expected to expand the practical application of PLA materials.

Acrylonitrile–butadiene–styrene (ABS) salami structure inspired PLLA composites with excellent stiffness-toughness balance

The stiffness-toughness balance of polymeric materials poses great challenges. Acrylonitrile–butadiene–styrene terpolymer (ABS) exhibits excellent mechanical and processing properties due to its unique “salami” morphologies. Inspired by this, we proposed a three-step reactive processing strategy to design high performance polylactide (PLLA) composites with the similar “sub-inclusion” microstructure. The reactive micro-crosslinked elastomer with bifunctional groups (RMCE) was first prepared by the blending of γ-aminopropyl-triethoxysilane (KH550) with the random copolymer of ethylene-acrylic ester-glycidyl methacrylate (EGMA). The following mixing of the minor PLLA with the RMCE leads to the double-ended fixing of polylactide molecular chain in the RMCE. The PLLA included reactive micro-crosslinked elastomers (IRCE) were then used to toughen PLLA, inducing the formation of PLLA alloys with the unique sub-inclusion morphology. Surprisingly, magnificent stiffness-toughness balance can be achieved for the obtained PLLA composites. This work opens up a new strategy for preparing high-performance polyester composites with excellent stiffness-toughness balance.

Effect of Acetylation of Two Cellulose Nanocrystal Polymorphs on Processibility and Physical Properties of Polylactide/Cellulose Nanocrystal Composite Film.

Polylactide (PLA) has become a popular alternative for petroleum-based plastics to reduce environmental pollution. The broader application of PLA is hampered by its brittle nature and incompatibility with the reinforcement phase. The aim of our work was to improve the ductility and compatibility of PLA composite film and investigate the mechanism by which nanocellulose enhances PLA polymer. Here, we present a robust PLA/nanocellulose hybrid film. Two different allomorphic cellulose nanocrystals (CNC-I and CNC-III) and their acetylated products (ACNC-I and ACNC-III) were used to realize better compatibility and mechanical performance in a hydrophobic PLA matrix. The tensile stress of the composite films with 3% ACNC-I and ACNC-III increased by 41.55% and 27.22% compared to pure PLA film, respectively. Compared to the CNC-I or CNC-III enhanced PLA composite films, the tensile stress of the films increased by 45.05% with 1% ACNC-I and 56.15% with 1% ACNC-III. In addition, PLA composite films with ACNCs showed better ductility and compatibility because the composite fracture gradually transitioned to a ductile fracture during the stretching process. As a result, ACNC-I and ACNC-III were found to be excellent reinforcing agents for the enhancement of the properties of polylactide composite film, and the replacement some petrochemical plastics with PLA composites would be very promising in actual life.

ПОЛІЛАКТИДНІ КОМПОЗИЦІЙНІ МАТЕРІАЛИ З ФУНГІБАКТЕРИЦИДНИМИ ВЛАСТИВОСТЯМИ

The regularities of obtaining polylactide film composite materials with simultaneous silver nanoparticles formation were researched. The influence of the nature of polylactide and its structure (amorphous and amorphous-crystalline), of the glycerin plasticizer on the solvent evaporationkinetics was determined. To give polylactide composites fungicidal properties, the silver reduction reaction by the interaction of argentum salts with polyvinylpyrrolidone was applied. A main technological scheme for obtaining films based on polylactide with fungicidal properties is proposed. Above mentioned provides effective practical usage of the films as packaging materials for food products and medicines.

Investigating the Properties and Characterization of a Hybrid 3D Printed Antimicrobial Composite Material Using FFF Process: Innovative and Swift.

Novel strategies and materials have gained the attention of researchers due to the current pandemic, the global market high competition, and the resistance of pathogens against conventional materials. There is a dire need to develop cost-effective, environmentally friendly, and biodegradable materials to fight against bacteria using novel approaches and composites. Fused filament fabrication (FFF), also known as fused deposition modeling (FDM), is the most effective and novel fabrication method to develop these composites due to its various advantages. Compared to metallic particles alone, composites of different metallic particles have shown excellent antimicrobial properties against common Gram-positive and Gram-negative bacteria. This study investigates the antimicrobial properties of two sets of hybrid composite materials, i.e., Cu-PLA-SS and Cu-PLA-Al, are made using copper-enriched polylactide composite, one-time printed side by-side with stainless steel/PLA composite, and second-time with aluminum/PLA composite respectively. These materials have 90 wt.% of copper, 85 wt.% of SS 17-4, 65 wt.% of Al with a density of 4.7 g/cc, 3.0 g/cc, and 1.54 g/cc, respectively, and were fabricated side by side using the fused filament fabrication (FFF) printing technique. The prepared materials were tested against Gram-positive and Gram-negative bacteria such as Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa), Salmonella Poona (S. Poona), and Enterococci during different time intervals (5 min, 10 min, 20 min, 1 h, 8 h, and 24 h). The results revealed that both samples showed excellent antimicrobial efficiency, and 99% reduction was observed after 10 min. Hence, three-dimensional (3D) printed polymeric composites enriched with metallic particles can be utilized for biomedical, food packaging, and tissue engineering applications. These composite materials can also provide sustainable solutions in public places and hospitals where the chances of touching surfaces are higher.