Polylactide Matrix Research Articles

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.

Structural features of polylactide and natural rubber films produced by solution casting

Composite film samples of polylactide-natural rubber with a rubber content of 5, 10 and 15 wt. % were obtained by the solution method. The study of morphology showed the presence of rubber inclusions in the form of drops in the polylactide matrix. Thermophysical characteristics were determined by differential scanning calorimetry. It was determined that when rubber was added, the peak of cold crystallization of polylactide disappears on melting thermograms, the melting temperature decreases by 1–4°C compared to 100% polylactide. The structure of the obtained compositions was studied by nuclear magnetic resonance, electron paramagnetic resonance, and X-ray diffraction. The diffraction patterns of the samples contain reflections characteristic of the crystalline α-form of polylactide.

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

Process-structure–property study of 3D-printed continuous fiber reinforced composites

3D-printed fiber-reinforced composites hold many advantages compared to conventional composites in terms of individualization, mass customization, design freedom, and tailoring the composite geometry to load-bearing specifications. Among candidate continuous fibers for reinforcement, basalt fibers (BFs) serve as an eco-friendly alternative with excellent physical and thermal properties. However, the applicability of continuous BFs to be used for 3D-printed polymer composites was rarely addressed in existing literature. Especially, the effects of impregnation density during manufacturing and the influence of local fiber distribution on the fracture behavior of BF-reinforced composites remain unclear. In this study, a solution coating process was employed as a fiber pre-treatment to improve the packing density of BF in a polylactide (PLA) matrix. The effects of the resulting fiber volume fraction (8–31 %) and the local fiber distribution on the tensile fracture mechanisms of 3D printed BF/PLA samples are thoroughly analyzed using three-dimensional X-ray tomography. It was found that at a concentration of 3 wt-%, the coating solution uniformly dispersed optimally between the fibers, resulting in improved impregnation densities of the BF in the PLA matrix. Thus, the resulting composite exhibited a tensile strength of 175 MPa and a Young’s modulus of 6.2 GPa, respectively. A viscoelastic constitutive model incorporating damage is used for property prediction within a composite design framework to be applied to 3D-printed BF/PLA structures. The model is validated with experimental data from tensile tests. The obtained results demonstrate the applicability of eco-friendly BF/PLA composites for 3D printing of industrial high-performance applications with an individualized property profile.

The Development of Polylactide Nanocomposites: A Review

Polylactide materials present a promising alternative to petroleum-based polymers due to their sustainability and biodegradability, although they have certain limitations in physical and mechanical properties for specific applications. The incorporation of nanoparticles, such as layered silicate (clay), carbon nanotubes, metal or metal oxide, cellulose nanowhiskers, can address these limitations by enhancing the thermal, mechanicals, barriers, and some other properties of polylactide. However, the distinct characteristics of these nanoparticles can affect the compatibility and processing of polylactide blends. In the polylactide nanocomposites, well-dispersed nanoparticles within the polylactide matrix result in excellent mechanical and thermal properties of the materials. Surface modification is required to improve compatibility and the crystallization process in the blended materials. This article reviews the development of polylactide nanocomposites and their applications. It discusses the general aspect of polylactides and nanomaterials as nanofillers, followed by the discussion of the processing and characterization of polylactide nanocomposites, including their applications. The final section summarizes and discusses the future challenges of polylactide nanocomposites concerning the future material’s requirements and economic considerations. As eco-friendly materials, polylactide nanocomposites offer significant potential to replace petroleum-based polymers.

Incorporation of Nanostructural Hydroxyapatite and Curcumin Extract from Curcuma longa L. Rhizome into Polylactide to Obtain Green Composite.

This study showed that a polylactide (PLA)-based composite filled with nanostructured hydroxyapatite (HAp) and a natural extract from the rhizome of Curcuma longa L. could provide an alternative to commonly used fossil-based plasticsfor food packaging. The incorporation of HAp into the PLA matrix had a positive effect on improving selected properties of the composites; the beneficial effect could be enhanced by introducing a green modifier in the form of an extract. Prior to the fabrication of the composite, the filler was characterized in terms of morphology and composition, and the composite was then fully characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman and Fourier transform infrared spectroscopy (FT-IR), and the mechanical, thermal, thermomechanical, and optical properties were investigated. The proposed material exhibits antioxidant properties against DPPH radicals and antibacterial performance against Escherichia coli (E. coli). The results showed that the nanocomposite has the highest antioxidant and antibacterial properties for 10 wt% HAp with an average diameter of rod-shaped structures below 100 nm. In addition, the introduction of turmeric extract had a positive effect on the tensile strength of the nanocomposites containing 1 and 5% HAp. As the resulting material adsorbs light in a specific wavelength range, it can be used in the medical sector, food-packaging, or coatings.

An engineered enzyme embedded into PLA to make self-biodegradable plastic.

Plastic production reached 400 million tons in 2022 (ref. 1), with packaging and single-use plastics accounting for a substantial amount of this2. The resulting waste ends up in landfills, incineration or the environment, contributing to environmental pollution3. Shifting to biodegradable and compostable plastics is increasingly being considered as an efficient waste-management alternative4. Although polylactide (PLA) is the most widely used biosourced polymer5, its biodegradation rate under home-compost and soil conditions remains low6-8. Here we present a PLA-based plastic in which an optimized enzyme is embedded to ensure rapid biodegradation and compostability at room temperature, using a scalable industrial process. First, an 80-fold activity enhancement was achieved through structure-based rational engineering of a new hyperthermostable PLA hydrolase. Second, the enzyme was uniformly dispersed within the PLA matrix by means of a masterbatch-based melt extrusion process. The liquid enzyme formulation was incorporated in polycaprolactone, a low-melting-temperature polymer, through melt extrusion at 70 °C, forming an 'enzymated' polycaprolactone masterbatch. Masterbatch pellets were integrated into PLA by melt extrusion at 160 °C, producing an enzymated PLA film (0.02% w/w enzyme) that fully disintegrated under home-compost conditions within 20-24 weeks, meeting home-composting standards. The mechanical and degradation properties of the enzymated film were compatible with industrial packaging applications, and they remained intact during long-term storage. This innovative material not only opens new avenues for composters and biomethane production but also provides a feasible industrial solution for PLA degradation.

Obtaining cellulose nanocrystals by acid hydrolysis procedure; and their use as reinforcement in polylactide biocomposites

In the first step of this study, purpose was to obtain and characterize cellulose nanocrystal (CNC) particles by applying sulfuric acid hydrolysis method to the starting material of microcrystalline cellulose (MCC) fibrils. After obtaining CNC particles via acid hydrolysis procedure, various analyses (SEM, DLS, FTIR, XRD, TGA) conducted revealed that average size of round shaped CNC particles was 38 nm with −30.4 mV Zeta potential value. They had monoclinic Cellulose-I crystal structure with Crystallinity Index of 80.6% and Crystallite Size of 3.39 nm. Their maximum thermal degradation temperature was 307°C with 23 wt% residue at 800°C. In the second step, the main aim was to investigate contribution of these obtained CNC particles when they were used as nano-reinforcement in polylactide (PLA) matrix biocomposites produced by industrially compatible melt mixing and shaping techniques. Mechanical tests revealed that when only 1 wt% CNC particles were incorporated into PLA matrix, increases in flexural strength and modulus were 29% and 51%; while increases in K IC and G IC fracture toughness values were 42% and 105%, respectively. Because, high degree of hydroxyl groups and presence of sulfate half-ester groups on the surfaces of CNC particles improved the interfacial interactions between the matrix and nano-reinforcement phase, leading to efficiency in strengthening and toughening mechanisms.

The Influence of Environmental Factors on the Degradation of PLA/Diatomaceous Earth Composites.

In the present study, tests were carried out on composite samples on a polylactide matrix containing 25% by weight of mineral filler in the form of diatomaceous earth, base, and silanized with GPTMOS (3-glycidoxypropyltrimethoxysilane), OTES (n-octyltriethoxysilane), and MTMOS (methyltrimethoxysilane) silanes. The addition of two types of waxes, synthetic polyamide wax and natural beeswax, were used as a factor to increase the rheological properties of the composites. The obtained samples were characterized in terms of the effect of filler silanization on the degradation rate of the composites. The tests were conducted under different conditioning conditions, i.e., after exposure to strong UV radiation for 250 and 500 h, and under natural sunlight for 21 days. The conditioning carried out under natural conditions showed that the modified samples exhibit up to twice the degradation rate of pure polylactide. The addition of synthetic wax to the composites increases the tendency to agglomerate diatomaceous earth, while natural wax has a positive effect on filler dispersion. For composites modified with GPTMOS and OTES silanes, it was noted that the addition of natural wax inhibited the degree of surface degradation, compared to the addition of synthetic wax, while the addition of MTMOS silane caused the opposite effect and samples with natural wax degraded more strongly. It was shown that, despite the high degree of surface degradation, the process does not occur significantly deep into the composite and stops at a certain depth.

Accelerated hydrolysis and degradation of polylactide nanocomposites using loaded silica nanocarriers

Polylactide (PLA) stands as a prominent commodity biodegradable polymer, yet its inherent slow biodegradation under certain conditions has been a persistent challenge. This study introduces a general approach for enhancing the biodegradation of PLA by employing silica nanoparticles (SiNPs) loaded with diverse cargoes. The SiNPs with diameters of ca. 100 nm are synthesized through a sol–gel process in an inverse microemulsion, enabling in situ loading with functional cargoes such as poly(acrylic acid), lignosulfonate, and chitosan. Surface grafting with PLA (PLA-grafted SiNPs) serves to prevent aggregation, thereby enhancing the dispersion of nanoparticles within the PLA matrix and improving composite properties preventing depletion. Lignin-loaded SiNPs demonstrate the capability to block UV light and enhance antioxidant activity in the composite compared to neat PLA. Notably, SiNPs loaded with poly(acrylic acid) and chitosan exhibit the capacity to accelerate PLA hydrolysis in aqueous environments, while lignin as cargo results in faster composting with an increased weight loss of ca. 20 wt% compared to neat PLA at only 1 wt% loading of SiNPs. This research outlines a versatile strategy utilizing SiNPs to address the slow biodegradation profile of PLA, offering valuable insights and a promising avenue for advancing the environmental sustainability of degradable polyester-based materials in diverse applications.

Polymer biodegradable films based on polylactide with additives to accelerate plant growth

Polylactic acid (polylactide) is by far the most widely researched and used biodegradable aliphatic polyester. Due to its properties, polylactide is one of the leading biomaterials in medicine, as well as in industry and agriculture. The work presents a variety of additives to the polylactide matrix to improve its properties. It has been established that polylactide is a highly crystalline polymer with water being the first factor of influence when incubated in soil for 28 days.

Structure and Properties of Polylactide Composites with TiO2-Lignin Hybrid Fillers.

The research presented in this article focuses on the use of inorganic-organic material, based on titanium dioxide and lignin, as a filler for polylactide (PLA) biocomposites. To date, no research has been conducted to understand the impact of hybrid fillers consisting of TiO2 and lignin on the supermolecular structure and crystallization abilities of polylactide. Polymer composites containing 1, 3 or 5 wt.% of hybrid filler or TiO2 were assessed in terms of their structure, morphology, and thermal properties. Mechanical properties, including tensile testing, bending, impact strength, and hardness, were discussed. The hybrid filler is characterized by a very good electrokinetic stability at pH greater than 3-4. The addition of all fillers led to a small decrease in the glass transition temperature but, most importantly, the addition of 1% of the hybrid filler to the PLA matrix increased the degree of crystallinity of the material by up to 20%. Microscopic studies revealed differences in the crystallization behavior and nucleation ability of fillers. The use of hybrid filler resulted in higher nucleation density and shorter induction time than in unfilled PLA or PLA with only TiO2. The introduction of small amounts of hybrid filler also affected the mechanical properties of the composites, causing an increase in bending strength and hardness. This information may be useful from a technological process standpoint and may also help to increase the range of applicability of biobased materials.

Expanded Perlite Mineral As a Natural Additive Used In Polylactide-Based Biodegradable Composites

Polylactide (PLA) is a biodegradable polymer derived from natural resources used in various applications ranging from medical to packaging. In this study, biocomposites were developed by combining perlite mineral (PER), a natural filler material, with a biodegradable PLA matrix in incorporated contaminations of 2.5%, 5%, 10%, and 15%. The purpose of this work is to obtain composites having low production costs while retaining their main properties. Mixing force measurements, tensile, Shore hardness, impact tests, melt flow indices (MFI), and scanning electron microscopy (SEM) evaluations were carried out on composite samples to determine the processing, mechanical, melt flow, and morphological aspects of the developed composites. When the tensile test data were reviewed, minor decreases in the tensile strength and % elongation parameters were noticed with perlite loadings. The inclusion of perlite powder significantly reduced the impact strength value of PLA. Composites with high amounts of PER displayed elevated hardness values. While the MFI results were analyzed, it was deduced that the addition of PER increased the melt flow characteristics of the PLA polymer. At low PER quantities, SEM micrographs displayed that PER particles were homogeneously distributed in the PLA phase. The particle homogeneity in the composite morphology deteriorated as the PER loading ratio in the composites rose. According to the overall results, the highest performance among composites was achieved in the sample including 2.5% PER, and this sample was considered to be the most suitable option for applications regarding PLA-based biocomposite material purposes.

The Influence of Urtica dioica and Vitis vinifera Fibers on the Thermal Properties and Flammability of Polylactide Composites.

This study focuses on examining the influence of bast fibers on the flammability and thermal properties of the polylactide matrix (PLA). For this purpose, Urtica dioica and Vitis vinifera fibers were subjected to two types of modifications: mercerization in NaOH solution (M1 route) and encapsulation in an organic PLA solution (M2 route). In a further step, PLA composites containing 5, 10, and 15 wt% of unmodified and chemically treated fibers were obtained. The results of the tests show that only biocomposites containing mercerized fibers had a nearly 20% reduced flammability compared to that of PLA. Moreover, the biofiller obtained in this way belongs to the group of flame retardants that generate char residue during combustion, which was also confirmed by TGA tests. The M2 modification route allowed to achieve higher mass viscosity than the addition of unmodified and M1-modified fibers. The reason is that fibers additionally encapsulated in a polymer layer impede the mobility of the chain segments. The inferior homogenization of the M2-modified fibers in the PLA matrix translated into a longer combustion time and only a 15% reduction in flammability.

Production of supertough and semiconductive PLA-based polymer blend nanocomposites by kinetic microstructural control

Polymer nanocomposites with superior multi-functional properties can be fabricated by tuning their morphology. In this work, a supertough and semiconductive polylactide (PLA)-based polymer blend nanocomposite (PBNANO) was produced for the first time via melt blending with a core-shell rubber (CSR) and carbon nanotubes (CNT). Reference binary blends (PLA/CSR and PLA/CNT) revealed that, when added separately, 20 wt% of CSR and 0.25 wt% of CNT were the suitable quantities to achieve a supertough and a semiconductive PLA-based material, respectively. Based on the obtained results, PLA/CSR/CNT PBNANOs with 20 wt% of CSR and CNT amounts between 0.15 and 0.50 wt% were prepared in one extrusion step. Although supertoughness was achieved in all the cases, the PBNANOs were insulating due to the selective localization of the CNT in the poly(methyl methacrylate) (PMMA) shell of the CSR and the good dispersion of the CSR nanoparticles. However, a supertough and semiconductive PLA-based PBNANO was obtained by a two-step melt compounding. Using this processing sequence, a worse dispersion of the CSR was obtained, allowing contact between some CSR nanoparticles. The differences in PBNANOs morphology prepared in one or two extrusion steps were determined by TEM and corroborated by rheological measurements. In the case of the two extrusion steps PBNANO, the CNT were located in both the PLA matrix and in the shell of the CSR. This morphological change enabled the PBNANO to be conductive, as the CNT percolation was achieved in this case while still remaining supertough.

Non-catalytic production of modified hydroxyapatite for biomedical applications

In this work, we propose a convenient non-catalytic method for modifying hydroxyapatite (HA) with lactic acid to obtain a composite material suitable for traumatology fasteners. The affinity of the modified HA for the polylactide matrix increases, which has a positive effect on the composite mechanical properties. The modification process is carried out with lactic acids solutions in ethanol. It was shown that hydroxyapatite modified with 10–30% solutions retains its structure according to IR spectroscopy and X-ray diffraction analysis, and when modified with a 50% solution, calcium hydrophosphate is formed. Studies of the mechanical properties have shown that the modulus increases by almost 1 GPa for composites with modified HA compared to unmodified hydroxyapatite reaching a value close to that of native cortical bone tissue.

Influence of the Morphological Characteristics and Filling of Polylactide Matrices on the Proliferation of HEK293T Cells

Influence of the Morphological Characteristics and Filling of Polylactide Matrices on the Proliferation of HEK293T Cells

Enhancing mechanical and shape memory properties of polylactide/polyamide elastomer blends via reactive blending with a chain extender

AbstractThe structure and properties of incompatible polylactide (PLA)/polyamide elastomer (PAE) blends were tailored by a chain extender specifically the styrene–glycidyl acrylate copolymer Joncryl ADR4368 (ADR). Various PLA/PAE/ADR blends with different compositions were prepared by melt blending, and their morphology, crystallization behavior, and mechanical and the shape memory properties were systematically investigated. The results showed a uniform dispersion of PAE particles in the PLA matrix for the PLA blends with a reduction in particle size upon the addition of ADR. The crystallization of PLA was retarded, which was confirmed by a decrease in the melt crystallization temperature and an increase in cold crystallization temperature in the PLA/PAE/ADR blends. Rheological analysis showed an improvement in the melt elasticity of the PLA/PAE binary blend due to the presence of ADR, possibly attributed to the formation of long‐chain‐branched copolymers at the interface. Notably, the PLA/PAE/ADR blend exhibited superior toughness, featuring an elongation at break of 288% and a notched impact strength of 37 kJ·m−2, along with a high shape memory fixation rate and recovery rate when the ADR content was 1 wt%. Furthermore, the underlying toughening mechanism was elucidated. This work may offer an industrially scalable relevant model to fabricate high‐performance PLA materials.

Exploring the Biomedical Potential of PLA/Dysprosium Phosphate Composites via Extrusion-Based 3D Printing: Design, Morphological, Mechanical, and Multimodal Imaging and Finite Element Modeling.

The present investigation demonstrates the feasibility of dysprosium phosphate (DyPO4) as an efficient additive in polylactide (PLA) to develop 3D printed scaffolds through the material extrusion (MEX) principle for application in bone tissue engineering. Initially, uniform sized particles of DyPO4 with tetragonal crystal setting are obtained and subsequently blended with different concentrations of PLA to extrude in the form of filaments. A maximum of 20 wt % DyPO4 in PLA matrix has been successfully drawn to yield a defect free filament. The resultant filaments were 3D printed through material extrusion methodology. The structural and morphological analysis confirmed the successful reinforcement of DyPO4 throughout the PLA matrix in all of the 3D printed components. All of the PLA/DyPO4 composites exhibited magnetic resonance imaging and computed tomography contrasting properties, which were dependent on the dysprosium content in the PLA matrix. The detailed mechanical evaluation of the 3D printed PLA/DyPO4 composites ensured good strength accomplished by the reinforcement of 5 wt % DyPO4 in PLA matrix, beyond which a gradual decline in the strength is noticed. Representative volume elements models were developed to realize the intrinsic property of the PLA/DyPO4 composite, and finite element analysis under both static and dynamic loading conditions has been performed to account for the reliability of experimental results.

Thermal and Mechanical Properties of Biocomposites Based on Polylactide and Tall Wheatgrass.

Biocomposites based on polylactic acid (PLA), tall wheatgrass (TWG), and hemp (H) were made by injection molding. The article discusses the impact of the agrofiller content on the composite properties, including thermal (DSC, DMA, and TG) and mechanical characteristics (tensile modulus, tensile strength, and impact strength). Generally, the introduction of a plant filler into the polylactide matrix reduced the thermal resistance of the resulting composites. Plant fillers influenced primarily the cold crystallization process, probably due to their nucleating properties. The addition of fillers to the PLA matrix resulted in an increased storage modulus across all tested temperatures compared to pure PLA. In the case of a composite with 50% of plant fillers, it was almost 118%. The mechanical properties of the tested composites depended significantly on the amount of plant filler used. It was observed that adding 50% of plant filler to PLA led to a twofold increase in tensile modulus and a decrease in tensile strength and impact strength by an average of 23 and 70%, respectively. It was determined that composites incorporating tall wheatgrass (TWG) particles exhibited a slightly elevated tensile modulus while showcasing a marginally reduced strength and impact resistance in comparison to composites containing hemp (H) components.