Morphological, Mechanical, and Thermal Characterization of Poly(Lactic Acid)/Cellulose Multifilament Fibers Prepared by Melt Spinning

Cellulose-Reinforced Polylactic Acid Composites for Three-Dimensional Printing Using Polyethylene Glycol as an Additive: A Comprehensive Review

Growing concerns about environmental issues and global warming have garnered increased attention in recent decades. Consequently, the use of materials sourced from renewable and biodegradable origins, produced sustainably, has piqued the interest of scientific researchers. Biodegradable and naturally derived polymers, such as cellulose and polylactic acid (PLA), have consistently been the focus of scientific investigation. The objective is to develop novel materials that could potentially replace conventional petroleum-based polymers, offering specific properties tailored for diverse applications while upholding principles of sustainability and technology as well as economic viability. Against this backdrop, the aim of this review is to provide a comprehensive overview of recent advancements in research concerning the use of polylactic acid (PLA) and the incorporation of cellulose as a reinforcing agent within this polymeric matrix, alongside the application of 3D printing technology. Additionally, a pivotal additive in the combination of PLA and cellulose, polyethylene glycol (PEG), is explored. A systematic review of the existing literature related to the combination of these materials (PLA, cellulose, and PEG) and 3D printing was conducted using the Web of Science and Scopus databases. The outcomes of this search are presented through a comparative analysis of diverse studies, encompassing aspects such as the scale and cellulose amount added into the PLA matrix, modifications applied to cellulose surfaces, the incorporation of additives or compatibilizing agents, variations in molecular weight and in the quantity of PEG introduced into the PLA/cellulose (nano)composites, and the resulting impact of these variables on the properties of these materials.

The synergistic effect of heterogeneous nucleation and stress-induced crystallization on supramolecular structure and performances of poly(lactic acid) melt-spun fibers

As a kind of bio-based polymer, poly (lactic acid) has potential application in fibers fields. Due to the weak nucleation ability, PLA crystallizes slowly and forms large spherulites during the forming process, which deteriorates the properties of PLA fibers. In this work, melt-spun method is employed for the fabrication of PLA/T composite fibers using succinate diphenyl dihydrazide (TMC-306) as the nucleating agent, and then the hot-drawing and heat setting is performed to the as-spun fibers. Compared with pure PLA fibers, PLA/T fibers show faster crystallization rate and improved performance due to the synergistic effect of heterogeneous nucleation and stress-induced crystallization. The characterization of non-isothermal crystallization behavior indicates that the peak crystallization temperature as well as crystallinity of PLA composites is increased to 121.5 °C and 36.78 % respectively by blending 0.3 wt% TMC-306. Meanwhile, the obtained PLA/0.3T composite fibers are highly crystallized and oriented at hot-drawing ratio of 2.4 folds and heat setting temperature of 100 °C, and the conformational stability is noticeably enhanced. Further, the tensile strength and storage modulus of PLA/0.3T composite fiber are 3.46 cN/dtex and 46,953 MPa respectively, which are increased by 42 % and 41 % compared with neat PLA fibers.

Recent advances on melt-spun fibers from biodegradable polymers and their composites

Biodegradable polymers have become important in different fields of application, where biodegradability and biocompatibility are required. Herein, the melt spinning of biodegradable polymers including poly(lactic acid), poly(butylene succinate), polyhydroxyalkanoate (PHA), poly(ɛ-caprolactone) and their biocomposites is critically reviewed. Biodegradable polymer fibers with added functionalities are in high demand for various applications, including biomedical, textiles, and others. Melt spinning is a suitable technique for the development of biodegradable polymer fibers in a large-scale quantity, and fibers with a high surface area can be obtained with this technique. The processing variables during spinning have a considerable impact on the resulting properties of the fibers. Therefore, in this review, the processing-property relationship in biodegradable polymers, blends, and their composites is provided. The morphological characteristics, load-bearing properties, and the potential application of melt-spun biodegradable fibers in various sectors are also provided.

Alternative modification by grafting in bamboo cellulose nanofibrils: A potential option to improve compatibility and tunable surface energy in bionanocomposites

Chemical modification in surface of cellulose nanofibrils CNFs (20 nm) from an endemic and non-significant value-added, Argentine bamboo, was developed. The modification in the CNFs was carried out with three simple routes using a low molecular weight polylactic acid synthesized in our laboratory (PLA1). The first step comprises of protection of the hydroxyl groups of PLA1 through a benzoylation (PLA1Bz). The next step consisted of the activation of carboxyl groups using thionyl chloride and the last reaction was the grafting of the modified PLA onto the CNFs (PLA1Bz-g-CNF). The covalently functionalization is confirmed by spectroscopically techniques as well as PLA1Bz-g-CNFs were characterized by thermal analyses. The PLA1Bz-g-CNFs were taken up such as nanocharges to improve properties of compatibilization and changing surface properties in films based on PLA. The comparison between the films with PLA1Bz-g-CNFs with respect to the physic mixture of the components (PLA1Bz/CNF), shows an improvement in the thermal, mechanical, and surface properties of the material, particularly when 5% of PLA1Bz-g-CNFs was added. The dispersive (γS D) component of film is increased in 36.1 mN/m respect to 29.3 mN/m from the films obtained with the physic mixture nanofibrils without modification and a plasticizing effect was noticed in the final material.

Poly(Lactic Acid)-Based Graft Copolymers: Syntheses Strategies and Improvement of Properties for Biomedical and Environmentally Friendly Applications: A Review

As a potential replacement for petroleum-based plastics, biodegradable bio-based polymers such as poly(lactic acid) (PLA) have received much attention in recent years. PLA is a biodegradable polymer with major applications in packaging and medicine. Unfortunately, PLA is less flexible and has less impact resistance than petroleum-based plastics. To improve the mechanical properties of PLA, PLA-based blends are very often used, but the outcome does not meet expectations because of the non-compatibility of the polymer blends. From a chemical point of view, the use of graft copolymers as a compatibilizer with a PLA backbone bearing side chains is an interesting option for improving the compatibility of these blends, which remains challenging. This review article reports on the various graft copolymers based on a PLA backbone and their syntheses following two chemical strategies: the synthesis and polymerization of modified lactide or direct chemical post-polymerization modification of PLA. The main applications of these PLA graft copolymers in the environmental and biomedical fields are presented.

High-Toughness Poly(Lactic Acid)/Starch Blends Prepared through Reactive Blending Plasticization and Compatibilization

In this study, poly(lactic acid) (PLA)/starch blends were prepared through reactive melt blending by using PLA and starch as raw materials and vegetable oil polyols, polyethylene glycol (PEG), and citric acid (CA) as additives. The effects of CA and PEG on the toughness of PLA/starch blends were analyzed using a mechanical performance test, scanning electron microscope analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy, X-ray diffraction, rheological analysis, and hydrophilicity test. Results showed that the elongation at break and impact strength of the PLA/premixed starch (PSt)/PEG/CA blend were 140.51% and 3.56 kJ·m-2, which were 13.4 and 1.8 times higher than those of pure PLA, respectively. The essence of the improvement in the toughness of the PLA/PSt/PEG/CA blend was the esterification reaction among CA, PEG, and starch. During the melt-blending process, the CA with abundant carboxyl groups reacted in the amorphous region of the starch. The shape and crystal form of the starch did not change, but the surface activity of the starch improved and consequently increased the adhesion between starch and PLA. As a plasticizer for PLA and starch, PEG effectively enhanced the mobility of the molecular chains. After PEG was dispersed, it participated in the esterification reaction of CA and starch at the interface and formed a branched/crosslinked copolymer that was embedded in the interface of PLA and starch. This copolymer further improved the compatibility of the PLA/starch blends. PEGs with small molecules and CA were used as compatibilizers to reduce the effect on PLA biodegradability. The esterification reaction on the starch surface improved the compatibilization and toughness of the PLA/starch blend materials and broadens their application prospects in the fields of medicine and high-fill packaging.

Biodegradable kinetics and behavior of bio-based polyblends under simulated aerobic composting conditions

The current study evaluates aerobic biodegradation of melt extruded poly(lactic acid) PLA based blends under composting conditions. Samples of neat PLA (NPLA) and bio-based polyblend composites of PLA/LLDPE (linear low-density polyethylene) having different concentration of MCC (microcrystalline cellulose crystal) were analyzed to understand the biodegradation behavior of these blends under simulated composting conditions. Biodegradation kinetics revealed that higher content of MCC and PLA accelerated the biodegradation process of the polymeric blends. Increase in the spherulite growth size and decrease in the spherulite density of the biodegraded samples confirmed the decline in amorphous portion of the test samples due to microbial assimilation, leaving behind the crystalline portion. Surface morphological analysis revealed that the samples of PLA/LLDPE/MCC blends underwent surface erosion prior to bulk biodegradation (50-80%) until the 90th day and the PLA formed fibril-like structures after degradation. This study would help in the design and preparation of biodegradable bio-based commercial blends in the future.

Thermoplastic Processing of PLA/Cellulose Nanomaterials Composites

Over the past decades, research has escalated on the use of polylactic acid (PLA) as a replacement for petroleum-based polymers. This is due to its valuable properties, such as renewability, biodegradability, biocompatibility and good thermomechanical properties. Despite possessing good mechanical properties comparable to conventional petroleum-based polymers, PLA suffers from some shortcomings such as low thermal resistance, heat distortion temperature and rate of crystallization, thus different fillers have been used to overcome these limitations. In the framework of environmentally friendly processes and products, there has been growing interest on the use of cellulose nanomaterials viz. cellulose nanocrystals (CNC) and nanofibers (CNF) as natural fillers for PLA towards advanced applications other than short-term packaging and biomedical. Cellulosic nanomaterials are renewable in nature, biodegradable, eco-friendly and they possess high strength and stiffness. In the case of eco-friendly processes, various conventional processing techniques, such as melt extrusion, melt-spinning, and compression molding, have been used to produce PLA composites. This review addresses the critical factors in the manufacturing of PLA-cellulosic nanomaterials by using conventional techniques and recent advances needed to promote and improve the dispersion of the cellulosic nanomaterials. Different aspects, including morphology, mechanical behavior and thermal properties, as well as comparisons of CNC- and CNF-reinforced PLA, are also discussed.