Processing technologies for poly(lactic acid)

Enhancing the mechanical properties of polylactic acid (PLA) composite films using Pueraria lobata root microcrystalline cellulose

To enhance the mechanical properties of polylactic acid (PLA) material, the PLA-based composite films are prepared by using Pueraria lobata (Willd.) Ohwi root microcrystalline cellulose (PRMCC) treated with 3-aminopropyl triethoxysilane (KH550) silane coupling agent as the dispersed phase through solvent casting method. The effects of the concentrations of PRMCC and KH550 as well as the KH550 pretreating condition (ethanol concentration) on the tensile properties of PLA-based composite films are investigated. The PLA-based composite film treated with 5 wt% PRMCC and 18 wt% KH550 (pretreated by 90 % EtOH) exhibits the greatest performance. Its elongation at break value is detected to be 4.0 %, 1.6 times as large as that of pure PLA film. The water absorption of the as-prepared PLA-based composite film is reduced from 0.49 % of the unmodified PLA/PRMCC film to 0.12 %. Moreover, the modified PLA-based composite film has a hydrophobic surface and exhibits good thermal stability. Compared with pure PLA film, the modified PLA-based composite film exhibits improved UV shielding performance with acceptable transparency. Furthermore, after adding poly(butylene adipate-co-terephthalate) (PBAT) to the composite system, the elongation at break of the PLA-based composite film is up to 7.2 %. This research can provide theoretical guidance for enhancing the performance of PLA products.

Dependence of the crystal structure on the d-units amount in semi-crystalline poly(lactic acid)

The study investigates the impact of the d-lactic acid units content on the crystallinity and crystal structure of commercial poly(lactic acid) (PLA) grades, which are copolymers of poly(l-lactic acid) (PLLA) containing a minor amount of d-units. As the d-units content increases, a detectable decrease in crystallinity was observed along with a simultaneous rise in mobile amorphous fraction (MAF) and a reduction in rigid amorphous fraction (RAF). The percentage of d-units was found not to significantly affect RAF thickness, suggesting that the d-units are not completely excluded from the crystals. The inclusion of d-units as defects in the PLA crystal lattice was confirmed by XRD analysis, which disclosed that the crystal phase gets gradually richer of d-units as the crystallization time evolves. FT-IR analysis proved that the incorporation of d-units in the crystal phase is promoted by the formation of local CH3···O=C interactions, similar to those massively active between PLLA and poly(d-lactic acid) (PDLA) in the stereocomplex. The establishment of these interactions leads to a contraction of the interplanar distances and a decrease in the crystal cell volume with increasing the crystallization time and the d-units percentage. In summary, the study proves that for PLA copolymers containing a d-units percentage at least up to about 8 %, d-units are included in the crystal lattice.

Enhanced strength, toughness and heat resistance of poly (lactic acid) with good transparency and biodegradability by uniaxial pre-stretching

Sustainable poly (lactic acid) (PLA) with excellent strength, toughness, heat resistance, transparency, and biodegradability was achieved by uniaxial pre-stretching at 70 °C. The effect of pre-stretched ratio (PSR) on the microstructure and properties of the PLA was investigated. The undrawn PLA was brittle. However, after pre-stretching, the elongation at break was increased significantly. The maximum value of 161.2 % was obtained at pre-stretching ratio (PSR) of 1.0. With the increase of PSR, the modulus and strength were improved obviously (from 1601 MPa and 60.2 MPa for undrawn PLA to 2932 MPa and 106.3 MPa for the ps-PLA at PSR =3.0). Meanwhile, the heat resistance of PLA was improved obviously with the increase of PSR. For the ps-PLA3.0, there were almost no deformation and shrink at 140 °C. Interestingly, after pre-stretching, the PLA still maintained the good transparency and biodegradability. The brittleness for undrawn PLA was attributed to the network structure of cohesional entanglements. After pre-stretching, the destruction of the network structure and formation of the orientation, mesophase and oriented nanosized crystalline phase lead to the increased the toughness, strength and heat resistance without sacrificing the transparency and biodegradability. This work provides a significant guidance for the fabrication of PLA material with excellent comprehensive performance including strength, toughness, heat resistance, transparency, and biodegradability.

Melt Compounding of Poly(lactic acid)-Based Composites: Blending Strategies, Process Conditions, and Mechanical Properties

Polylactic acid (PLA), derived from renewable resources, has the advantages of rigidity, thermoplasticity, biocompatibility, and biodegradability, and is widely used in many fields such as packaging, agriculture, and biomedicine. The excellent processability properties allow for melt processing treatments such as extrusion, injection molding, blow molding, and thermoforming in the preparation of PLA-based materials. However, the low toughness and poor thermal stability of PLA limit its practical applications. Compared with pure PLA, conditions such as processing technology, filler, and crystallinity affect the mechanical properties of PLA-based materials, including tensile strength, Young's modulus, and elongation at break. This review systematically summarizes various technical parameters for melt processing of PLA-based materials and further discusses the mechanical properties of PLA homopolymers, filler-reinforced PLA-based composites, PLA-based multiphase composites, and reactive composite strategies for PLA-based composites.

Enhancing functional properties of compostable materials with biobased plasticizers for potential food packaging applications

The demand of non-toxic and biobased plasticizers is substantially growing, particularly in biodegradable thermoplastics-based packaging applications. Herein, a derivative of citric acid (CITREM-LR10), usually used as food additive, was evaluated for the first time as plasticizer in PLA and Ecovio® biopolymers. Films containing 10 %(w/w) of CITREM-LR10 were prepared and compared with films plasticized with another biobased compound, SOFT-NSAFE, derived from acetic acid. The incorporation of both plasticizers provokes a slight reduction of the glass transition, however, only CITREM-LR10 was able to augment the elongation at break value of PLA films. A further evaluation of the films by Raman confocal microscopy showed the segregation of the CITREM-LR10 in microdomains, which could explain the enhanced elongation at break value, behaving as stress concentrators. In addition, CITREM-LR10 provides antimicrobial activity against S. aureus and both plasticizers give antioxidant properties, and almost negligible diffusion in food simulated solution. Composting studies showed that the plasticizers do not have effect on the disintegration rate of the films. In spite of these outstanding properties, the water vapour and oxygen barrier properties of the films worsen with its incorporation, therefore, the inclusion of fillers in the material together with the plasticizers would be necessary to improve such properties for food packaging applications.

The Development of Poly(lactic acid) (PLA)-Based Blends and Modification Strategies: Methods of Improving Key Properties towards Technical Applications-Review

The widespread use of poly(lactic acid) (PLA) from packaging to engineering applications seems to follow the current global trend. The development of high-performance PLA-based blends has led to the commercial introduction of various PLA-based resins with excellent thermomechanical properties. The reason for this is the progress in the field of major PLA limitations such as low thermal resistance and poor impact strength. The main purpose of using biobased polymers in polymer blends is to increase the share of renewable raw materials in the final product rather than its possible biodegradation. However, in the case of engineering applications, the focus is on achieving the required properties rather than maximizing the percentage of biopolymer. The presented review article discusses the current strategies to optimize the balance of the key features such as stiffness, toughness, and heat resistance of PLA-based blends. Improving of these properties requires molecular structural changes, which together with morphology, crystallinity, and the influence of the processing conditions are the main subjects of this article. The latest research in this field clearly indicates the high potential of using PLA-based materials in highly demanding applications. In the case of impact strength modification, it is possible to obtain values close to 800 J/m, which is a value comparable to polycarbonate. Significant improvement can also be confirmed for thermal resistance results, where heat deflection temperatures for selected types of PLA blends can reach even 130 °C after modification. The modification strategies discussed in this article confirm that a properly conducted process of selecting the blend components and the conditions of the processing technique allows for revealing the potential of PLA as an engineering plastic.

Physio-chemical degradation of single-use plastics in natural weather and marine environments

Plastic pollution has reached concerning levels globally, with single-use plastic products (SUPs) comprising at least 50% of plastic waste. This study investigates the physical and chemical degradation of frequently used SUPs, including petroleum-based and bio-based plastics, in natural Northern European coastal weather and marine environments over a three-year period from 2019 to 2022. Addressing a critical knowledge gap, this research was based on a hypothesis that real-world ageing studies on SUPs would produce more accurate time- and process-lines for their transformation from macro-to microplastics than are available today based on the modeling studies more frequently used. The study employs optical examination, mechanical testing, Fourier Transform Infrared (FTIR) spectroscopy, and Gas Chromatography-Mass Spectrometry (GC-MS) to determine and relate physical and chemical changes with time. The results indicate that SUPs undergo significantly faster degradation in natural weather than predicted to date. Photooxidation emerges as the primary degradation pathway for all SUPs, emphasizing the role of light in plastic breakdown. Importantly, physical degradation to microplastics in natural environments is not always associated with significant chemical changes such as breaking chemical bonds. Black SUPs exhibit greater resistance to visible light and ultraviolet radiation than equivalent white and transparent examples. In marine environments, SUPs degrade measurably slower than in air, their degradation slowing with increasing distance from the water surface. Our findings indicate the urgent need for strategies that mitigate the impacts of photo-oxidation of SUPs. Such strategies may include a focus on the removal of post-use SUPs from pavements, roads, beaches, and water surfaces where photo-oxidation is faster than underwater and underground. Preferential use of black SUPs over white or transparent should also be considered.

Lab-on-a-lollipop (LoL) platform for preventing food-induced toxicity: all-in-one system for saliva sampling and electrochemical detection of vanillin

Saliva has emerged as a primary biofluid for non-invasive disease diagnostics. Saliva collection involves using kits where individuals stimulate saliva production via a chewing device like a straw, then deposit the saliva into a designated collection tube. This process may pose discomfort to patients due to the necessity of producing large volumes of saliva and transferring it to the collection vessel. This work has developed a saliva collection and analysis device where the patient operates it like a lollipop, stimulating saliva production. The lollipop-mimic device contains yarn-based microfluidic channels that sample saliva and transfer it to the sensing zone embedded in the stem of the device. We have embedded electrochemical sensors in the lollipop platform to measure vanillin levels in saliva. Vanillin is the most common food flavoring additive and is added to most desserts such as ice cream, cakes, and cookies. Overconsumption of vanillin can cause side effects such as muscle weakness, and damage to the liver, kidneys, stomach, and lungs. We detected vanillin using direct oxidation at a laser-induced graphene (LIG) electrode. We showed a dynamic range of 2.5 μM to 30 μM, covering the physiologically relevant concentration of vanillin in saliva. The lab-on-a-lollipop platform requires only 200 μL of saliva and less than 2 minutes to fill the channels and complete the measurement. This work introduces the first sensor-embedded lollipop-mimic saliva collection and measurement system.

Material compatibility and processing challenges in droplet deposition modelling additive manufacturing: A study on pharmaceutical excipients Polyvinylpyrrolidone/vinyl acetate (PVP/VA) and Polycaprolactone (PCL)

Additive manufacturing (AM) enables the production of complex, lightweight, and customized components with superior quality. Selecting the right materials considering their thermal properties, printability, and layer adhesion is crucial in melting-based AM techniques. This study investigates Droplet Deposition Modelling (DDM), an innovative material extrusion process that utilizes thermoplastic granules. DDM is distinguished by its shorter manufacturing times and a wider range of materials, setting it apart from traditional material extrusion methods such as fused filament fabrication. We investigated the printability and part quality in DDM using two common pharmaceutical excipients: Polyvinylpyrrolidone/vinyl acetate 6:4 (PVP/VA), which is highly brittle, and Polycaprolactone (PCL), known for its low solubility and role in controlled drug release. Different ratios of PVP/VA and PCL were compounded via hot melt extrusion (HME) and used in DDM to study the impact of ingredient content on printability and part quality, employing geometrical models to assess material compatibility and printability. The study revealed that increasing PVP/VA content leads to higher viscosity, reduced flowability, and uneven deposition, with formulations of 80 % and 100 % PVP/VA showing poor processability. In contrast, formulations with 60 % and 40 % PVP/VA exhibited smooth processing and compatibility with DDM. We identified processing temperature and Drop Aspect Ratio (DAR) as key factors influencing material printability and part quality. Elevated processing temperatures and reduced DAR were found to increase interface temperatures, reduce diffusion, and potentially cause the 'elephant feet' issue. Additionally, smaller droplet sizes and material characteristics, such as higher interfacial tension in PCL, could lead to coalescence. Our findings highlight the complexities in optimizing DDM processing parameters and material blends, underscoring the need for careful formulation design to achieve high-quality 3D printed products.

Excellent mechanical and electromagnetic interference shielding properties of polylactic acid/polycaprolactone/multiwalled carbon nanotube composites enabled by a multilayer structure design

In this work, a special multilayer structure consisting of polylactic acid (PLA) and a co-continuous PLA/polycaprolactone (PCL)/multiwalled carbon nanotube (MWCNT) (ALM) composite with a double-percolated conductive network was fabricated via layer-assembly coextrusion. It was revealed that PLA domains located at the layer interface could serve as rivets properly linking adjacent layers. Such a nacre-like structure with alternately stacked rigid PLA and flexible ALM increased the fracture strain to 354.4%, nearly quadruple that of the PLA/PCL/MWCNT conventional blending composite with the same composition, while maintaining an excellent strength above 46.0 MPa. In addition, the multilayer composites showed a special frequency-selective electromagnetic interference (EMI) shielding performance, with tunable shielding peak positions controlled by the layer number. Their maximum EMI shielding effectiveness almost contributed by absorption loss could reach 49.8 dB, which originated from two aspects: one was the high electrical conductivity offered by the double-percolated distribution of MWCNTs, and the other was the multiple wave attenuation effect that occurred at the interfaces between PLA and ALM layers and the blend interfaces in ALM layers. This effort paves a new way for developing composites with outstanding mechanical and EMI shielding properties that can be extended to other polymeric composite systems.

Effect of Chemical Treatment of Cotton Stalk Fibers on the Mechanical and Thermal Properties of PLA/PP Blended Composites

Different chemical treatment methods were employed to modify the surface of cotton stalk fibers, which were then utilized as fillers in composite materials. These treated fibers were incorporated into polylactic acid/polypropylene melt blends using the melt blending technique. Results indicated that increasing the surface roughness of cotton stalk fibers could enhance the overall mechanical properties of the composite materials, albeit potentially leading to poor fiber-matrix compatibility. Conversely, a smooth fiber surface was found to improve compatibility with polylactic acid, while Si-O-C silane coating increased fiber regularity and interfacial interaction with the matrix, thereby enhancing heat resistance. The mechanical properties and thermal stability of the composite materials made from alkali/silane-treated fibers exhibited the most significant improvement. Furthermore, better dispersion of fibers in the matrix and more regular fiber orientation were conducive to increasing the overall crystallinity of the composite materials. However, such fiber distribution was not favorable for enhancing impact resistance, although this drawback could be mitigated by increasing the surface roughness of the reinforcing fibers.

In-situ self-reinforcement of amorphous polylactide (PLA) through induced crystallites network and its highly ductile and toughened PLA/poly(butylene adipate-co-terephthalate) (PBAT) blends

Crystallites of a semicrystalline polylactide (cPLA) were induced in an amorphous PLA (aPLA) and its blends with poly(butylene adipate-co-terephthalate) (PBAT) to achieve in-situ self-reinforced PLA based structures. The approach involved the melt blending of cPLA as a minor phase with aPLA and its blends with PBAT at processing temperatures below the crystal melting peak of cPLA. An injection molding (IM) process was first adopted to obtain self-reinforced PLA (SR-PLA) structures at aPLA/cPLA weight ratios of 100/0, 95/5, 90/10, 85/15, and 80/20. IM barrel and mold temperatures revealed crucial impacts on preserving the cPLA crystallites and thereby enhancing the final mechanical performance of SR-PLA (i.e., aPLA/cPLA) samples. SR-PLA samples at various aPLA/cPLA weight ratios of 100/0, 90/10, 80/20, and 70/30 were then melt blended with PBAT to produce SR-PLA/PBAT at a given ratio of 85/15. These blends were first prepared in an internal melt mixer (MM) to evaluate the rheological properties. The rheological analysis confirmed the significance of cPLA reinforcing efficiency within SR-PLA and its corresponding blends with PBAT. Similar SR-PLA/PBAT blends were also prepared using the IM process to explore their thermal and mechanical characteristics. The effect of cPLA concentrations in blends was distinctive, leading to significant enhancements in stain at break and toughness values. This was due to the increased crystallite network within the matrix, further refining PBAT droplets. Morphological analysis of the melt-processed blends through MM and IM also revealed that the PBAT droplets were further refined when the IM process was applied. The induced shear during the molding could have further elongated the cPLA crystallites towards a fiberlike structure, which could additionally cause the matrix viscosity to increase and refine the PBAT droplets.

Stability and Composting Behaviour of PLA-Starch Laminates Containing Active Extracts and Cellulose Fibres from Rice Straw

The stability and composting behaviour of monolayers and laminates of poly (lactic acid) (PLA) and starch with and without active extracts and cellulose fibres from rice straw (RS) were evaluated. The retrogradation of the starch throughout storage (1, 5, and 10 weeks) gave rise to stiffer and less extensible monolayers with lower water vapour barrier capacity. In contrast, the PLA monolayers, with or without extract, did not show marked changes with storage. However, these changes were more attenuated in the bilayers that gained water vapour and oxygen barrier capacity during storage, maintaining the values of the different properties close to the initial range. The bioactivity of the active films exhibited a slight decrease during storage, so the antioxidant capacity is better preserved in the bilayers. All monolayer and bilayer films were fully composted within 90 days but with different behaviour. The bilayer assembly enhanced the biodegradation of PLA, whose monolayer exhibited a lag period of about 35 days. The active extract reduced the biodegradation rate of both mono- and bilayers but did not limit the material biodegradation within the time established in the Standard. Therefore, PLA-starch laminates, with or without the valorised fractions from RS, can be considered as biodegradable and stable materials for food packaging applications.

A versatile route for the fabrication of micro-patterned polylactic-acid (PLA)-based membranes with tailored morphology via breath figure imprinting

Breath figure imprinting, based on surface instabilities combined with fast polymer evaporation in a humid environment, enables the creation of micro-patterned membranes with tailored pore sizes. Despite being a simple procedure, it is still challenging to fully understand the dynamics behind the formation of hierarchical structuring. In this work, we used the breath figure technique to prepare porous PLA-based (polylactic acid) membranes with two distinctive additives, polyvinylidene fluoride (PVDF) and zinc oxide nanoparticles (ZnO NPs). The selection of these additives was governed by their unique properties and the potential synergistic effects; when blended with PLA, the addition of NPs leads to more uniform structures with tunable characteristics and potential multifunctionality. This article sheds light on the multifaced interactions that intricate the interplays between PLA, PVDF, and ZnO, thus governing their assembly. Through a comprehensive investigation, we scrutinize the impact of blending PVDF and different concentrations of ZnO NPs on the morphology and chemical properties of the final self-assembled PLA membranes while presenting an advanced understanding of the potential applications of PLA-self-assembly porous membranes in various industrial sectors.

Forefront Research of Foaming Strategies on Biodegradable Polymers and Their Composites by Thermal or Melt-Based Processing Technologies: Advances and Perspectives

The last few decades have witnessed significant advances in the development of polymeric-based foam materials. These materials find several practical applications in our daily lives due to their characteristic properties such as low density, thermal insulation, and porosity, which are important in packaging, in building construction, and in biomedical applications, respectively. The first foams with practical applications used polymeric materials of petrochemical origin. However, due to growing environmental concerns, considerable efforts have been made to replace some of these materials with biodegradable polymers. Foam processing has evolved greatly in recent years due to improvements in existing techniques, such as the use of supercritical fluids in extrusion foaming and foam injection moulding, as well as the advent or adaptation of existing techniques to produce foams, as in the case of the combination between additive manufacturing and foam technology. The use of supercritical CO2 is especially advantageous in the production of porous structures for biomedical applications, as CO2 is chemically inert and non-toxic; in addition, it allows for an easy tailoring of the pore structure through processing conditions. Biodegradable polymeric materials, despite their enormous advantages over petroleum-based materials, present some difficulties regarding their potential use in foaming, such as poor melt strength, slow crystallization rate, poor processability, low service temperature, low toughness, and high brittleness, which limits their field of application. Several strategies were developed to improve the melt strength, including the change in monomer composition and the use of chemical modifiers and chain extenders to extend the chain length or create a branched molecular structure, to increase the molecular weight and the viscosity of the polymer. The use of additives or fillers is also commonly used, as fillers can improve crystallization kinetics by acting as crystal-nucleating agents. Alternatively, biodegradable polymers can be blended with other biodegradable polymers to combine certain properties and to counteract certain limitations. This work therefore aims to provide the latest advances regarding the foaming of biodegradable polymers. It covers the main foaming techniques and their advances and reviews the uses of biodegradable polymers in foaming, focusing on the chemical changes of polymers that improve their foaming ability. Finally, the challenges as well as the main opportunities presented reinforce the market potential of the biodegradable polymer foam materials.

Unveiling the detrimental effects of polylactic acid microplastics on rice seedlings and soil health

The environmental impact of biodegradable polylactic acid microplastics (PLA-MPs) has become a global concern, with documented effects on soil health, nutrient cycling, water retention, and crop growth. This study aimed to assess the repercussions of varying concentrations of PLA-MPs on rice, encompassing aspects such as growth, physiology, and biochemistry. Additionally, the investigation delved into the influence of PLA-MPs on soil bacterial composition and soil enzyme activities. The results illustrated that the highest levels of PLA-MPs (2.5%) impaired the photosynthesis activity of rice plants and hampered plant growth. Plants exposed to the highest concentration of PLA-MPs (2.5%) displayed a significant reduction of 51.3% and 47.7% in their root and shoot dry weights, as well as a reduction of 53% and 49% in chlorophyll a and b contents, respectively. The activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) in rice leaves increased by 3.1, 2.8, 3.5, and 5.2 folds, respectively, with the highest level of PLA-MPs (2.5%). Soil enzyme activities, such as CAT, urease, and dehydrogenase (DHA) increased by 19.2%, 10.4%, and 22.5%, respectively, in response to the highest level of PLA-MPs (2.5%) application. In addition, PLA-MPs (2.5%) resulted in a remarkable increase in the relative abundance of soil Proteobacteria, Nitrospirae, and Firmicutes by 60%, 31%, and 98.2%, respectively. These findings highlight the potential adverse effects of PLA-MPs on crops and soils. This study provides valuable insights into soil-rice interactions, environmental risks, and biodegradable plastic regulation, underscoring the need for further research.

"Flexible-strong" polylactic acid porous membrane via tailored polymerization degree of lactic acid side-chains grafting for passive daytime radiative cooler

Aerogel possesses the advantages of high specific surface area, low density, and high porosity, which have shown great application in thermal regulation due to its efficient light scattering capability. However, traditional polymer-based aerogels have poor mechanical properties and lack ductility in outdoor applications, the cooling efficiency of the material is easily affected by damage during transportation, installation, and environmental factors. In this work, combining the porous nature of aerogels and the high ductility of membranes, a polylactic acid-based porous membrane cooler was developed by combining a regular honeycomb surface porous structure design and physical/chemical modification to enhance flexibility, using a simple non-solvent induced phase separation method. This porous membrane exhibits both super-flexibility (116 % elongation at break) and porous characteristics. It achieves a sub-ambient temperature decrease of 4-6 °C under direct sunlight. The optimized porous membrane demonstrates high solar reflectance (94 % of peak reflectivity, 90 % of average reflectivity) and strong infrared emissivity (96 % of peak emissivity, 91 % of average emissivity), it also maintains a solar peak reflectivity of 91 % under 100 % tensile strain and 1000 bending cycles, the cooler still maintains a cooling effect of 2-5 °C below ambient temperature. This work paves the way for developing mechanical flexible and strong radiative coolers for thermal regulation.

Development of Biocompatible Electrospun PHBV-PLLA Polymeric Bilayer Composite Membranes for Skin Tissue Engineering Applications

Bilayer electrospun fibers aimed to be used for skin tissue engineering applications were fabricated for enhanced cell attachment and proliferation. Different ratios of PHBV-PLLA (70:30, 80:20, and 90:10 w/w) blends were electrospun on previously formed electrospun PHBV membranes to produce their bilayers. The fabricated electrospun membranes were characterized with FTIR, which conformed to the characteristic peaks assigned for both PHBV and PLLA. The surface morphology was evaluated using SEM analysis that showed random fibers with porous morphology. The fiber diameter and pore size were measured in the range of 0.7 ± 0.1 µm and 1.9 ± 0.2 µm, respectively. The tensile properties of the bilayers were determined using an electrodynamic testing system. Bilayers had higher elongation at break (44.45%) compared to the monolayers (28.41%) and improved ultimate tensile strength (7.940 MPa) compared to the PHBV monolayer (2.450 MPa). In vitro cytotoxicity of each of the scaffolds was determined via culturing MC3T3 (pre-osteoblastic cell line) on the membranes. Proliferation was evaluated using the Alamar Blue assay on days 3, 7, and 14, respectively. SEM images of cells cultured on membranes were taken in addition to bright field imaging to visually show cell attachment. Fluorescent nuclear staining performed with DAPI was imaged with an inverted fluorescent microscope. The fabricated bilayer shows high mechanical strength as well as biocompatibility with good cell proliferation and cell attachment, showing potential for skin substitute applications.

Development of Flame-Retardant Polylactic Acid Formulations for Additive Manufacturing

Polymeric materials, renowned for their lightweight attributes and design adaptability, play a pivotal role in augmenting fuel efficiency and cost-effectiveness in railway vehicle development. The tailored formulation of compounds, specifically designed for additive manufacturing, holds significant promise in expanding the use of these materials. This study centers on poly(lactic acid) (PLA), a natural-based biodegradable polymeric material incorporating diverse halogen-free flame retardants (FRs). Our investigation scrutinizes the printability and fire performance of these formulations, aligning with the European railway standard EN 45545-2. The findings underscore that FR in the condensed phase, including ammonium polyphosphate (APP), expandable graphite (EG), and intumescent systems, exhibit superior fire performance. Notably, FR-inducing hydrolytic degradation, such as aluminum hydroxide (ATH) or EG, reduces polymer molecular weight, significantly impacting PLA's mechanical performance. Achieving a delicate balance between fire resistance and mechanical properties, formulations with APP as the flame retardant emerge as optimal. This research contributes to understanding the fire performance and printability of 3D-printed PLA compounds, offering vital insights for the rail industry's adoption of polymeric materials.

Effect of Plasticization/Annealing on Thermal, Dynamic Mechanical, and Rheological Properties of Poly(Lactic Acid)

This study investigates the use of low molecular weight poly(ethylene glycol) (PEG) as a plasticizer for poly(lactic acid) (PLA). PLA/PEG blend films were prepared using the solvent casting method with varying mixing ratios. The films were analyzed using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and dynamic rheological analysis. The results indicate that the addition of PEG as a plasticizer affects the thermal and mechanical properties of the PLA/PEG blend films. The study found that the glass transition and cold crystallization temperatures decreased with increasing PEG content up to 20 wt%, while the crystallinity and crystallization rate increased. The blends with up to 20 wt% PEG were miscible, but phase separation occurred when the plasticizer content was increased to 30 wt%. Subsequently, amorphous samples of neat PLA and PLA plasticized with 10 wt% of PEG underwent annealing at various temperatures (Ta = 80-120 °C) for durations ta of 1 and 24 h. The samples were then analyzed using DSC and DMA. The addition of PEG to PLA altered the content of α' and α crystalline forms compared to neat PLA at a given (Ta; ta) and favored the formation of a mixture of α' and α crystals. The crystallinity achieved upon annealing increased with increasing Ta or ta and with the incorporation of PEG.

Improvement in Crystallization, Thermal, and Mechanical Properties of Flexible Poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) Bioplastic with Zinc Phenylphosphate

Poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLLA-PEG-PLLA) shows promise for use in bioplastic applications due to its greater flexibility over PLLA. However, further research is needed to improve PLLA-PEG-PLLA's properties with appropriate fillers. This study employed zinc phenylphosphate (PPZn) as a multi-functional filler for PLLA-PEG-PLLA. The effects of PPZn addition on PLLA-PEG-PLLA characteristics, such as crystallization and thermal and mechanical properties, were investigated. There was good phase compatibility between the PPZn and PLLA-PEG-PLLA. The addition of PPZn improved PLLA-PEG-PLLA's crystallization properties, as evidenced by the disappearance of the cold crystallization temperature, an increase in the crystallinity, an increase in the crystallization temperature, and a decrease in the crystallization half-time. The PLLA-PEG-PLLA's thermal stability and heat resistance were enhanced by the addition of PPZn. The PPZn addition also enhanced the mechanical properties of the PLLA-PEG-PLLA, as demonstrated by the rise in ultimate tensile stress and Young's modulus. We can conclude that the PPZn has potential for use as a multi-functional filler for the PLLA-PEG-PLLA composite due to its nucleating-enhancing, thermal-stabilizing, and reinforcing ability.

Evaluation of bioplastics biodegradation under simulated landfill conditions

Bioplastics that are generated from renewable sources have been regarded as an alternative to conventional plastics. Polylactic acid (PLA) is one of the mostly produced bioplastics because of its long shelf life for various applications. Even though bioplastics have drawn attention recently, their ultimate fate in landfills is still unknown. In this study, a standardized laboratory-scale lysimeter experiment was performed for the simulation of landfill conditions in order to evaluate the biodegradability of PLA during municipal solid waste stabilization. The reactors were loaded with municipal solid waste (MSW) taken from an operating landfill, certified PLA cups, and seed sludge. Various phases of landfill stabilization were simulated; hence, the reactors were operated under aerobic, semi-aerobic, and anaerobic conditions, respectively. Throughout the operation, both leachate and biogas generation in the reactors were regularly monitored. At the end of each phase, bioplastic cups were removed from the reactors, gently cleaned, weighed, and examined under a scanning electron microscope (SEM). The experimental results indicated that bioplastics did not undergo significant biodegradation during the first two stabilization phases (aerobic and semi-aerobic). On the other hand, it was observed that the cups were much softer and whiter at the end of the anaerobic phase. The weight of cups decreased by 12.8% on average, and their surfaces were prominently damaged after the completion of the last phase indicating the potential signs of biodegradation.

Toward exclusive stereocomplex crystallization of high-molecular-weight poly(L-lactic acid)/poly(D-lactic acid) blends with outstanding heat resistance via incorporating selective nucleating agents

In high molecular weight poly(L-lactic acid)/poly(D-lactic acid) (HMW PLLA/PDLA) blends, the construction of exclusive stereocomplex crystals (SC) with high crystallinity and strong melt memory remains a great challenge. In the present study, various norbornene dicarboxylate complexes (TMXNa, Mg, Al, or Ca) were employed as the stereo-selective nucleating agents (NAs), and their effect on the crystallization characteristics, rheological behavior, and heat resistance of PLLA/PDLA blends were thoroughly studied. Strikingly, TMX-Al facilitated the construction of exclusive SC with over 50 % crystallinity and excellent melt memory. The dense SC crystals network structure boosted the heat resistance of L/D-xAl blends with a VST as high as 145 °C. The strengthened intermolecular interaction fostered the generation of pre-ordered structure in the melt and enhanced chain interdiffusion, which contributed to intermolecular nucleation and SC crystallization in L/D-xAl blend. This study opens up a new avenue for melt processing and application development of SC-PLA materials.

Self-Reinforced PTLG Copolymer with Shish Kebab Structures and a Bionic Surface as Bioimplant Materials for Tissue Engineering Applications

Green and biodegradable materials with great mechanical properties and biocompatibility will offer new opportunities for next-generation high-performance biological materials. Herein, the novel oriented shish kebab crystals of a novel poly(trimethylene carbonate-lactide-glycolide) (PTLG) vascular stent are first reported to be successfully fabricated through a feasible solid-state drawing process to simultaneously enhance the mechanical performance and biocompatibility. The crystal structure of this self-reinforced vascular stent was transformed from spherulites to a shish kebab crystal, which indicates the mechanical interlocking effect and prevents the lamellae from slipping with a significant improvement of mechanical strength to 333 MPa. Meanwhile, it is different from typical biomedical polymers with smooth surface structures, and the as-obtained PTLG vascular stent exhibits a bionic surface morphology with a parallel micro groove and ridge structure. These ridges and grooves were attributed to the reorganization of cytoskeleton fiber bundles following the direction of blood flow shear stress. The structure and parameters of these morphologies were highly similar to the inner surface of blood vessels of the human, which facilitates cell adhesion growth to improve its proliferation, differentiation, and activity on the surface of PTLG.

Synthesis of L-Lactide from Lactic Acid and Production of PLA Pellets: Full-Cycle Laboratory-Scale Technology

Lactide is one of the most popular and promising monomers for the synthesis of biocompatible and biodegradable polylactide and its copolymers. The goal of this work was to carry out a full cycle of polylactide production from lactic acid. Process conditions and ratios of reagents were optimized, and the key properties of the synthesized polymers were investigated. The influence of synthesis conditions and the molecular weight of lactic acid oligomers on the yield of lactide was studied. Lactide polymerization was first carried out in a 500 mL flask and then scaled up and carried out in a 2000 mL laboratory reactor setup with a combined extruder. Initially, the lactic acid solution was concentrated to remove free water; then, the oligomerization and synthesis of lactide were carried out in one flask in the presence of various concentrations of tin octoate catalyst at temperatures from 150 to 210 °C. The yield of lactide was 67-69%. The resulting raw lactide was purified by recrystallization in solvents. The yield of lactide after recrystallization in butyl acetate (selected as the optimal solvent for laboratory purification) was 41.4%. Further, the polymerization of lactide was carried out in a reactor unit at a tin octoate catalyst concentration of 500 ppm. Conversion was 95%; Mw = 228 kDa; and PDI = 1.94. The resulting products were studied by differential scanning calorimetry, NMR spectroscopy and gel permeation chromatography. The resulting polylactide in the form of pellets was obtained using an extruder and a pelletizer.

Poly(ethylene succinate-co-lactic acid) as a Multifunctional Additive for Modulating the Miscibility, Crystallization, and Mechanical Properties of Poly(lactic acid)

Polymer blending offers an effective and economical approach to overcome the performance limitations of poly(lactic acid) (PLA). In this study, a series of copolymers poly(ethylene succinate-co-lactic acid) (PESL) were synthesized, featuring lactic acid (LA) contents that ranged from 20 to 86 wt %. This synthesis involved a one-pot industrial melt polycondensation process using succinic acid (SA), ethylene glycol (EG), and LA, catalyzed by titanium tetraisopropoxide (TTP). The goal was to produce a fully biobased copolymer expected to exhibit partial miscibility with pure poly(lactic acid) (PLA). To assess the capability of PESL copolymers in toughening PLA, we conducted tensile testing on PLA/PESL blends containing 15 wt % PESL. As a result, an elongation at break for the blends with 15 wt % loading of the copolymer PESL72 was directly enhanced to 250% with an ultimate strength of 35 MPa, compared to brittle PLA with less 10% tensile length. The morphological features of interfacial adhesion before and after tensile failure were measured by scanning electron microscopy (SEM). A significant enhancement in the chain mobility of the PLA/PESL blends was further evidenced by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). These findings hold promise for the development of functional packaging materials based on PLA. The proposed copolymer design, which boasts strong industrial feasibility, can serve as a valuable guide for enhancing the toughness of PLA.

Elucidating intermolecular forces to improve compatibility of kraft lignin in poly(lactic acid)

Owing to its abundant supply from renewable resources, lignin has emerged as a promising functional filler for the development of sustainable composite materials. However, achieving good interfacial compatibility between lignin and synthetic polymers, particularly poly (lactic acid) (PLA), remains a fundamental challenge. To advance the development of high-performance bio-based composites incorporating lignin and PLA, our study has scrutinized to unravel the nuances of interfacial binding interactions with the lignin and PLA composite system. Molecular level and experimental examinations were employed to decipher fundamental mechanisms governing and demonstrating the interfacial adhesion. We synthesized casted films of lignin/PLA and acetylated lignin/PLA at varying weight percentages of lignin (5%, 10%, and 20%) and comprehensively investigated their physicochemical and mechanical properties. The inclusion of acetylated lignin in the composites resulted in improved mechanical strength and Young's modulus, while the glass transition temperature and melting point were reduced compared to neat PLA. Systematic variations in these properties revealed distinct compatibility behaviors between unmodified lignin and acetylated lignin when incorporated into PLA. Molecular dynamics (MD) simulation results elucidated that the observed changes in material properties were primarily attributed to the acetylation of lignin. Acetylated lignin exhibited lower Coulombic interaction energy and higher van der Waals forces, indicating a stronger affinity to PLA and a reduced propensity for intermolecular aggregation compared to unmodified lignin. Our findings highlight the critical role of controlling intermolecular interactions and lignin aggregation to develop PLA composites with predictable performance for new applications, such as functional packaging materials.

Super-tough poly(lactic acid)/silicone rubber thermoplastic vulcanizates: The organic and inorganic synergistic interfacial compatibilization

Polymer modification using silicone rubber represents a promising avenue for enhancing physico-mechanical properties. However, achieving optimal performance through direct blending is hindered by the poor interface compatibility between silicone rubber and the matrix. In this study, we prepared super-tough thermoplastic vulcanizates (TPVs) of polylactic acid/silicone rubber through dynamic vulcanization with PLA, methyl vinyl silicone rubber (MVQ), glycidyl methacrylate grafted MVQ (MVQ-g-GMA), and fumed silica nanoparticles (SiO2). The impact of the SiO2 addition in MVQ on the morphology, mechanical properties, crystallization, and thermal properties of the TPVs was investigated. The results showed that MVQ-g-GMA and SiO2 exhibited a synergistic compatibilization effect significantly improving the interfacial adhesion between PLA and MVQ. Therefore, the impact and tensile strength of the TPVs increased from 8.0 kJ/m2 and 22.2 MPa to 62.6 kJ/m2 and 36.7 MPa, respectively. Moreover, the TPVs also presented good low-temperature toughness with a maximum impact strength of 40.4 kJ/m2 at -20 °C. Additionally, improvements in thermal stability and crystallization rate were also observed. Overall, combining organic and inorganic synergistic compatibilization is a feasible and effective method to fabricate outstanding low-temperature toughness to PLA.

Shelf life extending of probiotic beef patties with polylactic acid-ajwain essential oil films and stress effects on Bacillus coagulans

Meat and meat products are prone to the microbial and chemical spoilage, due to the high nutritional content. This study investigated the effect of polylactic acid (PLA) films incorporated with ajwain essential oil (AEO) on microbial (total viable count [TVC], psychrotrophic bacterial count [PTC], Enterobacteriaceae, Pseudomonas spp., yeast and mold (Y&M), and also Bacillus coagulans [BCG]), chemical (pH, peroxide value [PV], thiobarbituric acid-reactive substance [TBARS], and TVN values), and sensorial properties of beef patties, as well as survivability of BCG during refrigerated storage. Results showed that all microbial counts of samples were significantly increased, except BCG, during storage but the lowest TVC of samples was achieved in samples wrapped with PLA-1% AEO (8 log colony forming units per gram [CFU/g]) at 12th of storage, which is significantly lower than control treatments (10.66 log CFU/g). The best results in all treatments are those wrapped by PLA-1% AEO in all evaluated characteristics. At the final day of storage, PTC (8.82 log CFU/g), Enterobacteriaceae (5.05 log CFU/g), Pseudomonas spp. (9.08 log CFU/g), Y&M (4.69 log CFU/g), and also pH (4.5), PV (5.12 meq/kg), TBARS (2.92 MDA/kg), and TVN (14.43 mgN/100 g) values of PLA-1% AEO treatments were significantly lower than control samples. AEO-PLA films reduce the survival of BCG in raw patties, which reached 6.19 log CFU/g in PLA-1% AEO treatments, although increasing the concentration of AEO in packaging PLA films led to the maintenance of BCG viability during the cooking process by increasing the AEO in PLA films. Overall, results showed shelf life of beef patties is extended 3 days more (150%) by wrapping with PLA films incorporated with 1% AEO.

Unexpected Periodicity in Cationic Group 5 Initiators for the Ring-Opening Polymerization of Lactones

ε-Caprolactone (ε-CL) adducts of cationic, amine tris(phenolate)-supported niobium(V) and tantalum(V) ethoxides initiate the ring-opening polymerization of lactones. The Ta(V) species prepared and applied catalytically herein exhibits higher activity in the ring-opening polymerization (ROP) of ε-caprolactone than the previously reported, isostructural Nb(V) complex, contradicting literature comparisons of Nb(V)- and Ta(V)-based protocols. Both systems also initiate the ROP of δ-valerolactone and rac-β-butyrolactone, kinetic studies confirming retention of higher activity by the Ta congener. Polymerizations of rac-β-butyrolactone and δ-valerolactone were previously unrealized under Group V- or Ta-mediated conditions, respectively, although the former has afforded only low molecular weight, cyclic poly-3-hydroxybutyrate. Cationic ethoxo-Nb(V) and -Ta(V) δ-valerolactone adducts are also reported, demonstrating the facility of δ-valerolactone as a ligand and the generality of the synthetic method. Both δ-valerolactone-bearing complexes initiate the ROP of ε-caprolactone, δ-valerolactone, and rac-β-butyrolactone. Accordingly, we have elucidated trends in reactivity and investigated the initiation mechanism for such systems, the insertion event being predicated upon intramolecular nucleophilic attack on the coordinated lactone by the adjacent alkoxide moiety. This mechanism enables quantitative, stoichiometric installation of a single monomer residue distinct from the bulk of the polymer chain, and permits modification of polymer properties via both manipulation of the molecular architecture and tuning of the polymerization kinetics, and thus dispersity, through hitherto inaccessible independent control of the initiation event.

Evaluation of poly(lactic acid) and ECOVIO based biocomposites loaded with antimicrobial sodium phosphate microparticles

Herein, biobased composite materials based on poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) as matrices, sodium hexametaphosphate microparticles (E452i, food additive microparticles, 1 and 5 wt%) as antimicrobial filler and acetyl tributyl citrate (ATBC, 15 wt%) as plasticizer, were developed for potential food packaging applications. Two set of composite films were obtained by melt-extrusion and compression molding, i) based on PLA matrix and ii) based on Ecovio® matrix (PLA/PBAT blend). Thermal characterization by thermogravimetric analysis and differential scanning calorimetry demonstrated that the incorporation of E452i particles improved thermal stability and crystallinity, while the mechanical test showed an increase in the Young's modulus. E452i particles also provide antimicrobial properties to the films against food-borne bacteria Listeria innocua and Staphylococcus aureus, with bacterial reduction percentages higher than 50 % in films with 5 wt% of particles. The films also preserved their disintegradability as demonstrated by an exhaustive characterization of the films under industrial composting conditions. Therefore, the results obtained in this work reveal the potential of these biocomposites as appropriated materials for antibacterial and compostable food packaging films.

Metastable FeMg particles for controlling degradation rate, mechanical properties, and biocompatibility of Poly(l-lactic) acid (PLLA) for orthopedic applications

Poly(l-lactic) acid (PLLA) is commonly used in bioabsorbable medical implants, but it suffers from slow degradation rate and rapid decline in mechanical properties for orthopedic applications. To address this drawback, recent research has explored the use of Mg as a filler for PLLA, resulting in composites with improved degradation rate and cytocompatibility compared to neat PLLA. In this study, FeMg powder particles were proposed as fillers for PLLA to investigate the potential of PLLA/FeMg composites for bioabsorbable implants. Cylinder specimens of PLLA, PLLA/Fe, PLLA/Mg and PLLA/FeMg were prepared using solvent casting followed by thermo-molding. The microstructure, thermal behavior, in vitro degradation behavior in simulated body fluid, mechanical properties and cytocompatibility of these composites were examined. The results indicate that the presence of FeMg particles prevents the deterioration of the composite mechanical properties, at least up to 14 days. Once a certain amount of degradation of the composite is reached, the degradation is faster than that of PLLA. Direct cytotoxicity assays revealed that pre-osteoblast MC3T3-E1 cells successfully adhered to and proliferated on the PLLA/FeMg surface. The inclusion of a low percentage of Mg into the Fe lattice not only accelerated the degradation rate of Fe but also improved its cytocompatibility. The enhanced degradation rate, mechanical properties, and osteoconductive properties of this composite make it a promising option for temporary orthopedic biomedical devices.

Multistimuli-Responsive Actuators Derived from Natural Materials for Entirely Biodegradable and Programmable Untethered Soft Robots

Untethered soft robots have attracted growing attention due to their safe interaction with living organisms, good flexibility, and accurate remote control. However, the materials involved are often nonbiodegradable or are derived from nonrenewable resources, leading to serious environmental problems. Here, we report a biomass-based multistimuli-responsive actuator based on cuttlefish ink nanoparticles (CINPs), wood-derived cellulose nanofiber (CNF), and bioderived polylactic acid (PLA). Taking advantage of the good photothermal conversion performance and exceptionally hygroscopic sensitivity of the CINPs/CNF composite (CICC) layer and the opposite thermally induced deformation behavior between the CICC layer and PLA layer, the soft actuator exhibits reversible deformation behaviors under near-infrared (NIR) light, humidity, and temperature stimuli, respectively. By introducing patterned or alignment structures and combining them with a macroscopic reassembly strategy, diverse programmable shape-morphing from 2D to 3D such as letter-shape, coiling, self-folding, and more sophisticated 3D deformations have been demonstrated. All of these deformations can be successfully predicted by finite element analysis (FEA) . Furthermore, this actuator has been further applied as an untethered grasping robot, weightlifting robot, and climbing robot capable of climbing a vertical pole. Such actuators consisting entirely of biodegradable materials will offer a sustainable future for untethered soft robots.

Properties of Stereocomplex PLA for Melt Spinning

Fibers made from biopolymers are one solution for conserving both resources and the environment. However, these fibers currently have limited strengths, which limit their use for textile applications. In this paper, a biopolymer stereocomplex poly(-lactide) (scPLA) formation on a technical scale of high-molecular-weight poly(D-lactide) (PDLA) and poly(L-lactide) (PLLA) is presented. This scPLA material is the basis for further research to develop scPLA yarns in melt spinning with technical strengths for technical application. scPLA is compared with standard and commercially available semi-crystalline PLA for the production of fibers in melt spinning (msPLA) with textile strengths. Differential scanning calorimetry (DSC) gives a degree of crystallization of 59.7% for scPLA and 47.0% for msPLA. X-ray diffraction (XRD) confirms the pure stereocomplex crystal structure for scPLA and semi-crystallinity for msPLA. scPLA and msPLA are also compared regarding their processing properties (rheology) in melt spinning. While complex viscosity of scPLA is much lower compared to msPLA, both materials show similar viscoelastic behavior. Thermal gravimetric analysis (TGA) shows the influence of the molecular weight on the thermal stability, whereas essentially the crystallinity influences the biodegradability of the PLA materials.

Effect of a Self-Assembled Nucleating Agent on the Crystallization Behavior and Spherulitic Morphology of Poly(lactic acid)

Herein, decanedioic acid dibenzoylhydrazide (DDBH) was used as a nucleating agent to improve the crystallization of poly(lactic acid) (PLA). The formation of DDBH assemblies in PLA melts at different concentrations was systematically investigated. The DDBH (0.5-0.9 wt %) recrystallized as dendrite-like structures during the isothermal crystallization process, and the crystal morphology of PLA underwent a morphological change from spherical form to a similar dendritic crystal form. Differential scanning calorimetry and in situ wide-angle X-ray diffraction analysis results showed that crystallizability and overall crystallization rate of PLA were enhanced by the addition of DDBH. The half-crystallization time at 120 °C reduced to 0.28 min compared to pure PLA (6.12 min), after adding 0.9 wt % DDBH. Moreover, the crystallinity and lamellar thickness of crystalline PLA increased, while the size of the microcrystal of PLA decreased with an increase in DDBH content. The heat deflection temperatures of PLA/DDBH blends increased and hence heat resistance improved.

Petal-like Patterning of Polylactide/Poly (Butylene Succinate) Thin Films Induced by Phase Separation

Biodegradable plastics are attracting attention as a solution to the problems caused by plastic waste. Among biodegradable plastics, polylactide (PLA) and poly (butylene succinate) (PBS) are particularly noteworthy because of their excellent biodegradability. However, the drawbacks of their mechanical properties prompts the need to compound them to achieve the desired strength. The characteristics of the interface of the composite material determine the realization of its final performance. The study of the interface and microstructure of composites is essential for the development of products from degradable polymers. The morphology evolution and microcrystal structure of spin-casted fully biodegradable (PLA/PBS) blend films were investigated using atomic force microscopy (AFM)-based nanomechanical mapping. Results show that intact blend films present an obvious phase separation, where the PBS phase is uniformly dispersed in the PLA phase in the form of pores. Furthermore, the size and number of the PBS phase have a power exponential relationship and linear relationship with PBS loading, respectively. Intriguingly, after annealing at 80 °C for 30 min, the PLA phase formed an orderly petal-like microcrystalline structure centered on the PBS phase. Moreover, the microcrystalline morphology changed from a "daisy type" to a "sunflower type" with the increased size of the PBS phase. Since the size of the PBS phase is controllable, a new method for preparing microscopic patterns using fully biodegradable polymers is proposed.

Towards ductile and high barrier poly(L-lactic acid) ultra-thin packaging film by regulating chain structures for efficient preservation of cherry tomatoes

The irreconcilable paradox between barrier performance and ductility is a "stumbling block" restricting the development of poly(L-lactic acid) (PLLA) films in the packaging industry. In this work, we reported the fabrication of an ultra-thin PLLA-based film with barrier properties and ductility by adjusting the polarity and conformational behavior of the polymer chains. Firstly, a novel unsaturated poly(L-lactic acid-co-butyrate itaconate) P(LA-BI) copolymer containing CC double bonds was synthesized using melt polycondensation. The results reveal that the addition of 60 % of P(LA-BI) enables PLLA film to achieve an elongation at a break of 83.6 % due to P(LA-BI) containing partially branched structures, which resulted in the polymer chains being arranged more in a high-energy gg conformer. Meanwhile, because of the large number of CO polar groups in P(LA-BI), PLLA/P(LA-BI)60 film show CO2 and O2 permeability coefficients (CDP and OP) of 1.8 and 0.45 × 10-8 g·m·m-2·h-1·Pa-1 respectively, which means that it has excellent gas barrier properties. Moreover, PLLA/P(LA-BI)60 film shows a 33.3 % increase in CO2/O2 ratio and an excellent ultraviolet (UV) barrier performance compared to neat PLLA. Preservation results suggested that the CO2 and O2 levels within the package could be regulated by varying the amount of P(LA-BI) added. Among them, PLLA/P(LA-BI)40 film generated a more desirable CO2 and O2 atmosphere for cherry tomatoes preservation, which was reflected by the delaying of senescence, discoloration, and decay, inhibition of oxidative cell damage through reduced malondialdehyde production, and maintenance of nutritional and flavor substances in cherry tomatoes. This PLLA-based film offers the advantages of operational simplicity, environmental friendliness, and inexpensive cost, making it great promising for food preservation and other applications requiring barrier properties and ductility.

Compatibilizing Biodegradable Poly(lactic acid)/polybutylene adipate-co-terephthalate Blends via Reactive Graphene Oxide for Screw-Based 3D Printing

Vinyl-functionalized graphene oxide (VGO) was used as a reactive compatibilizer to prepare poly(lactic acid)/polybutylene adipate-co-terephthalate (PLA/PBAT) blends. The linear rheological and scanning electron microscopy results confirmed that the VGO nanosheets were quite efficient in compatibilizing PLA/PBAT blends. The size of the PBAT dispersed phase was remarkably decreased in the presence of VGO nanosheets. Moreover, the VGO nanosheets exhibited strong nucleating effects on the crystallization process of PLA. The crystallinity of PLA component in the compatibilized blend with various VGO nanosheets was higher than 40%, upon the cooling rate of 20 °C/min. The prepared PLA/PBAT pellets were applied to 3D printing, using a self-developed screw-based 3D printer. The results showed that all the prepared PLA/PBAT blend pellets can be 3D printed successfully. The notched Izod impact test results showed that, in the presence of VGO, an increase of at least 142% in impact strength was achieved for PLA/PBAT blend. This could be attributed to the compatibilizing effect of the VGO nanosheets. Thus, this work provides a novel way to prepare tough PLA-based materials for 3D printing.

Evaluation of Physicochemical Properties of a Hydroxyapatite Polymer Nanocomposite for Use in Fused Filament Fabrication

Over the last decade, there has been an increasing interest in the use of bioceramics for biomedical purposes. Bioceramics, specifically those made of calcium phosphate, are commonly used in dental and orthopaedic applications. In this context, hydroxyapatite (HA) is considered a viable option for hard tissue engineering applications given its compositional similarity to bioapatite. However, owing to their poor mechanobiology and biodegradability, traditional HA-based composites have limited utilisation possibilities in bone, cartilage and dental applications. Therefore, the efficiency of nano HA (nHA) has been explored to address these limitations. nHA has shown excellent remineralising effects on initial enamel lesions and is widely used as an additive for improving existing dental materials. Furthermore, three-dimensional printing (3DP) or fused deposition modelling that can be used for creating dental and hard tissue scaffolds tailored to each patient's specific anatomy has attracted considerable interest. However, the materials used for producing hard tissue with 3DP are still limited. Therefore, the current study aimed to develop a hybrid polymer nanocomposite composed of nHA, nanoclay (NC) and polylactic acid (PLA) that was suitable for 3DP. The nHA polymer nanocomposites were extruded into filaments and their physiochemical properties were evaluated. The results showed that the addition of nHA and NC to the PLA matrix significantly increased the water absorption and contact angle. In addition, the hardness increased from 1.04 to 1.25 times with the incorporation of nHA. In sum, the nHA-NC-reinforced PLA could be used as 3DP filaments to generate bone and dental scaffolds, and further studies are needed on the biocompatibility of this material.

Coordination of ε-Caprolactone to a Cationic Niobium(V) Alkoxide Complex: Fundamental Insight into Ring-Opening Polymerization via Coordination-Insertion

We report three niobium-based initiators for the catalytic ring-opening polymerization (ROP) of ε-caprolactone, exhibiting good activity and molecular weight control. In particular, we have prepared on the gram-scale and fully characterized a monometallic cationic alkoxo-Nb(V) ε-caprolactone adduct representing, to the best of our knowledge, an unprecedented example of a metal complex with an intact lactone monomer and a functional ROP-initiating group simultaneously coordinated at the metal center. At 80 °C, all three systems initiate the immortal solution-state ROP of ε-caprolactone via a coordination-insertion mechanism, which has been confirmed through experimental studies, and is supported by computational data. Natural bond orbital calculations further indicate that polymerization may necessitate isomerization about the metal center between the alkoxide chain and the coordinated monomer. The observations made in this work are expected to inform mechanistic understanding both of amine tris(phenolate)-supported metal alkoxide ROP initiators, including various highly stereoselective systems for the polymerization of lactides and of coordination-insertion-type ROP protocols more broadly.

Applications of poly(lactic acid) in bone tissue engineering: A review article

BACKGROUND

Bone tissue engineering is a promising approach to large-scale bone regeneration. This involves the use of an artificial extracellular matrix or scaffold and osteoblasts to promote osteogenesis and ossification at defect sites. Scaffolds are constructed using biomaterials that typically have properties similar to those of natural bone.

METHOD

In this study, which is a review of the literature, various evidences have been discussed in the field of Poly Lactic acid (PLA) polymer application and modifications made on it in order to induce osteogenesis and repair bone lesions.

RESULTS

PLA is a synthetic aliphatic polymer that has been extensively used for scaffold construction in bone tissue engineering owing to its good processability, biocompatibility, and flexibility in design. However, PLA has some drawbacks, including low osteoconductivity, low cellular adhesion, and the possibility of inflammatory reactions owing to acidic discharge in a living environment. To overcome these issues, a combination of PLA and other biomaterials has been introduced.

CONCLUSIONS

This short review discusses PLA's characteristics of PLA, its applications in bone regeneration, and its combination with other biomaterials.

Molecular insight into toughening induced by core-shell structure formation in starch-blended bioplastic composites

Binary and ternary blends with poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and thermoplastic starch (TPS) were prepared by a melt process to produce biodegradable biomass plastics with both economical and good mechanical properties. The mechanical and structural properties of each blend were evaluated. Molecular dynamics (MD) simulations were also conducted to examine the mechanisms underlying the mechanical and structural properties. PLA/PBS/TPS blends showed improved mechanical properties compared with PLA/TPS blends. The PLA/PBS/TPS blends with a TPS ratio of 25-40 wt% showed higher impact strength than PLA/PBS blends. Morphology observations showed that in the PLA/PBS/TPS blends, a structure similar to that of core-shell particles with TPS as the embedding phase and PBS as the coating phase was formed, and that the trends in morphology and impact strength changes were consistent. The MD simulations suggested that PBS and TPS tightly adhered to each other in a stable structure at a specific intermolecular distance. From these results, it is clear that PLA/PBS/TPS blends are toughened by the formation of a core-shell structure in which the TPS core and the PBS shell adhered well together and stress concentration and energy absorption occurred in the vicinity of the core-shell structure.

A Review of Biodegradable Plastics: Chemistry, Applications, Properties, and Future Research Needs

Environmental concerns over waste plastics' effect on the environment are leading to the creation of biodegradable plastics. Biodegradable plastics may serve as a promising approach to manage the issue of environmental accumulation of plastic waste in the ocean and soil. Biodegradable plastics are the type of polymers that can be degraded by microorganisms into small molecules (e.g., H2O, CO2, and CH4). However, there are misconceptions surrounding biodegradable plastics. For example, the term "biodegradable" on product labeling can be misconstrued by the public to imply that the product will degrade under any environmental conditions. Such misleading information leads to consumer encouragement of excessive consumption of certain goods and increased littering of products labeled as "biodegradable". This review not only provides a comprehensive overview of the state-of-the-art biodegradable plastics but also clarifies the definitions and various terms associated with biodegradable plastics, including oxo-degradable plastics, enzyme-mediated plastics, and biodegradation agents. Analytical techniques and standard test methods to evaluate the biodegradability of polymeric materials in alignment with international standards are summarized. The review summarizes the properties and industrial applications of previously developed biodegradable plastics and then discusses how biomass-derived monomers can create new types of biodegradable polymers by utilizing their unique chemical properties from oxygen-containing functional groups. The terminology and methodologies covered in the paper provide a perspective on directions for the design of new biodegradable polymers that possess not only advanced performance for practical applications but also environmental benefits.

Biodegradable Polymer-Based Drug-Delivery Systems for Ocular Diseases

Ocular drug delivery is a challenging field due to the unique anatomical and physiological barriers of the eye. Biodegradable polymers have emerged as promising tools for efficient and controlled drug delivery in ocular diseases. This review provides an overview of biodegradable polymer-based drug-delivery systems for ocular diseases with emphasis on the potential for biodegradable polymers to overcome the limitations of conventional methods, allowing for sustained drug release, improved bioavailability, and targeted therapy. Natural and synthetic polymers are both discussed, highlighting their biodegradability and biocompatibility. Various formulation strategies, such as nanoparticles, hydrogels, and microemulsions, among others, are investigated, detailing preparation methods, drug encapsulation, and clinical applications. The focus is on anterior and posterior segment drug delivery, covering glaucoma, corneal disorders, ocular inflammation, retinal diseases, age-related macular degeneration, and diabetic retinopathy. Safety considerations, such as biocompatibility evaluations, in vivo toxicity studies, and clinical safety, are addressed. Future perspectives encompass advancements, regulatory considerations, and clinical translation challenges. In conclusion, biodegradable polymers offer potential for efficient and targeted ocular drug delivery, improving therapeutic outcomes while reducing side effects. Further research is needed to optimize formulation strategies and address regulatory requirements for successful clinical implementation.

Role of Rheology in Morphology Development and Advanced Processing of Thermoplastic Polymer Materials: A Review

This review presents fundamental knowledge and recent advances pertaining to research on the role of rheology in polymer processing, highlights the knowledge gap between the function of rheology in various processing operations and the importance of rheology in the development, characterization, and assessment of the morphologies of polymeric materials, and offers ideas for enhancing the processabilities of polymeric materials in advanced processing operations. Rheology plays a crucial role in the morphological evolution of polymer blends and composites, influencing the type of morphology in the case of blends and the quality of dispersion in the cases of both blends and composites. The rheological characteristics of multiphase polymeric materials provide valuable information on the morphologies of these materials, thereby rendering rheology an important tool for morphological assessment. Although rheology extensively affects the processabilities of polymeric materials in all processing operations, this review focuses on the roles of rheology in film blowing, electrospinning, centrifugal jet spinning, and the three-dimensional printing of polymeric materials, which are advanced processing operations that have gained significant research interest. This review offers a comprehensive overview of the fundamentals of morphology development and the aforementioned processing techniques; moreover, it covers all vital aspects related to the tailoring of the rheological characteristics of polymeric materials for achieving superior morphologies and high processabilities of these materials in advanced processing operations. Thus, this article provides a direction for future advancements in polymer processing. Furthermore, the superiority of elongational flow over shear flow in enhancing the quality of dispersion in multiphase polymeric materials and the role of extensional rheology in the advanced processing operations of these materials, which have rarely been discussed in previous reviews, have been critically analyzed in this review. In summary, this article offers new insights into the use of rheology in material and product development during advanced polymer-processing operations.

Enhanced Degradability, Mechanical Properties, and Flame Retardation of Poly(Lactic Acid) Composite with New Zealand Jade (Pounamu) Particles

Plastic pollution has become a global concern, demanding urgent attention and concerted efforts to mitigate its environmental impacts. Biodegradable plastics have emerged as a potential solution, offering the prospect of reduced harm through degradation over time. However, the lower mechanical strength and slower degradation process of biodegradable plastics have hindered their widespread adoption. In this study, we investigate the incorporation of New Zealand (NZ) jade (pounamu) particles into poly(lactic acid) (PLA) to enhance the performance of the resulting composite. We aim to improve mechanical strength, flame retardation, and degradability. The material properties and compatibility with 3D printing technology were examined through a series of characterization techniques, including X-ray diffraction, dispersive X-ray fluorescence spectrometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, 3D printing, compression molding, pycnometry, rheometry, tensile tests, three-point bending, and flammability testing. Our findings demonstrate that the addition of NZ jade particles significantly affects the density, thermal stability, and mechanical properties of the composites. Compounding NZ jade shows two different changes in thermal stability. It reduces flammability suggesting potential flame-retardant properties, and it accelerates the thermal degradation process as observed from the thermogravimetric analysis and the inferred decrease in molecular weight through rheometry. Thus, the presence of jade particles can also have the potential to enhance biodegradation, although further research is needed to assess its impact. The mechanical properties differ between compression-molded and 3D-printed samples, with compression-molded composites exhibiting higher strength and stiffness. Increasing jade content in composites further enhances their mechanical performance. Th results of this study contribute to the development of sustainable solutions for plastic pollution, paving the way for innovative applications and a cleaner environment.

Effect of Sterilization on Bone Implants Based on Biodegradable Polylactide and Hydroxyapatite

Medical devices intended for implantation must be, in accordance with the legal provisions in force in the European Union, sterile. The effect of sterilization on the structural and thermal properties of implants, made by 3D printing from biodegradable polylactide and hydroxyapatite in a proportion of 9/1 by weight, was evaluated. The implants were sterilized using three different methods, i.e., steam sterilization, ethylene oxide sterilization, and electron beam radiation sterilization. As a result of the assessment of the structural properties of the implants after sterilization, a change in the molecular weight of the raw material of the designed implants was found after each of the performed sterilization methods, while maintaining similar characteristics of the thermal properties and functional groups present.

Interactions, Structure and Properties of PLA/lignin/PBAT Hybrid Blends

Poly(butylene adipate-co-terephthalate) (PBAT) was added to poly(lactic acid) (PLA)/lignin blends to decrease the considerable stiffness and brittleness of the blends. Two- and three-component blends were prepared in a wide composition range through homogenization in an internal mixer followed by compression molding. Interactions among the components were estimated by comparing the solubility parameters of the materials used and through thermal analysis. Mechanical properties were characterized by tensile testing. The structure of the blends was studied using scanning electron (SEM) and digital optical (DOM) microscopy. The results showed that the interactions between PBAT and lignin are somewhat stronger than those between PLA and the other two components. The maleic anhydride grafted PLA added as a coupling agent proved completely ineffective; it does not modify the interactions. The structural analysis confirmed the immiscibility of the components; the structure of the blends was heterogeneous at each composition. A dispersed structure formed when the concentration of one of the components was small, while, depending on lignin content, an interpenetrating network-like structure developed and phase inversion took place in the range of 30-60 vol% PBAT content. Lignin was located mainly in the PBAT phase. Properties were determined by the relative amount of PBAT and PLA; the addition of lignin deteriorated properties, mainly the deformability of the blends. Other means, such as reactive processing, must be used to improve compatibility and blend properties. The results contribute considerably to a better understanding of structure-property correlations in lignin-based hybrid blends.

Converting textile waste into value-added chemicals: An integrated bio-refinery process

The rate of textile waste generation worldwide has increased dramatically due to a rise in clothing consumption and production. Here, conversion of cotton-based, colored cotton-based, and blended cotton-polyethylene terephthalate (PET) textile waste materials into value-added chemicals (bioethanol, sorbitol, lactic acid, terephthalic acid (TPA), and ethylene glycol (EG)) via enzymatic hydrolysis and fermentation was investigated. In order to enhance the efficiency of enzymatic saccharification, effective pretreatment methods for each type of textile waste were developed, respectively. A high glucose yield of 99.1% was obtained from white cotton-based textile waste after NaOH pretreatment. Furthermore, the digestibility of the cellulose in colored cotton-based textile wastes was increased 1.38-1.75 times because of the removal of dye materials by HPAC-NaOH pretreatment. The blended cotton-PET samples showed good hydrolysis efficiency following PET removal via NaOH-ethanol pretreatment, with a glucose yield of 92.49%. The sugar content produced via enzymatic hydrolysis was then converted into key platform chemicals (bioethanol, sorbitol, and lactic acid) via fermentation or hydrogenation. The maximum ethanol yield was achieved with the white T-shirt sample (537 mL/kg substrate), which was 3.2, 2.1, and 2.6 times higher than those obtained with rice straw, pine wood, and oak wood, respectively. Glucose was selectively converted into sorbitol and LA at a yield of 70% and 83.67%, respectively. TPA and EG were produced from blended cotton-PET via NaOH-ethanol pretreatment. The integrated biorefinery process proposed here demonstrates significant potential for valorization of textile waste.

Development and Characterization of Polylactic Acid (PLA)-Based Nanocomposites Used for Food Packaging

The present study is focused on polylactic acid (PLA) blending with bio nanoadditives, such as Tonsil^® (clay) and Aerosil^®, to obtain nanocomposites for a new generation of food packaging. The basic composition was enhanced using Sorbitan oleate (E494) and Proviplast as plasticizers, increasing the composite samples' stability and their mechanical strength. Four mixtures were prepared: S1 with Tonsil^®; S2 with Aerosil^®; S3 with Aerosil^® + Proviplast; and S4 with Sabosorb. They were complexly characterized by FT-IR spectroscopy, differential scanning calorimetry, mechanical tests on different temperatures, and absorption of the saline solution. FTIR shows a proper embedding of the filler component into the polymer matrix and DSC presents a good stability at the living body temperature for all prepared samples. Micro and nanostructural aspects were evidenced by SEM and AFM microscopy, revealing that S3 has the most compact and uniform filler distribution and S4 has the most irregular one. Thus, S3 evidenced the best diametral tensile strength and S4 evidenced the weakest values. All samples present the best bending strength at 18 °C and fair values at 4 °C, with the best values being obtained for the S1 sample and the worst for S4. The lack of mechanical strength of the S4 sample is compensated by its best resistance at liquid penetration, while S1 is more affected by the liquid infiltrations. Finally, results show that PLA composites are suitable for biodegradable and disposable food packages, and the desired properties could be achieved by proper adjustment of the filler proportions.