Poly Lactic Acid Research Articles

Effect of Oligoricinoleic Acid on Degradation of Polylactic Acid

ABSTRACT The objective of this research is to explore the impact of oligoricinoleic acid (ORA) on the degradation of polylactic acid (PLA). ORA was synthesized from ricinoleic acid using tin (II) 2-ethylhexanoate as a catalyst. The chemical structures of the obtained ORA were confirmed by Fourier-transform infrared spectrometer (FT-IR) and proton nuclear magnetic resonance spectroscopy (1H-NMR). PLA/ORA films were prepared through the casting method by varying ORA concentrations as 0.1%wt, 0.3%wt, 0.5%wt, 1.0 wt%, and 3.0%wt. Degradation of the films via hydrolysis was studied by soaking the films in deionized water and stirring at 120 rpm in an incubator at 37°C. Alterations in the structure and properties of the films were investigated after soaking for 7, 14, 21, and 28 days using ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectrometer (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and universal testing machine (UTM). Gel permeation chromatography (GPC) was performed to confirm the decrease in molecular weight (MW). The presence of 3%wt ORA could promote both ductility and degradation of PLA films. ORA further enhances thermal stability, indicating potential for prevention of thermal degradation during melt processing.

Biodegradable polylactic acid emulsion ink based on carbon nanotubes and silver for printed pressure sensors

Investigating biodegradable and biocompatible materials for electronic applications can lead to tangible outcomes such as developing green-electronic devices and reducing the amount of e-waste. The proposed emulsion-based conducting ink formulation takes into consideration circular economy and green principles throughout the entire process, from the selection of materials to the production process. The ink is formulated using the biopolymer polylactic acid dissolved in a sustainable solvent mixed with water, along with conductive carbon nanotubes (CNTs) and silver flakes as fillers. Hybrid conductive fillers can lower the percolation threshold of the ink and the production costs, while maintaining excellent electrical properties. The coating formed after the deposition of the ink, undergoes isothermal treatment at different temperatures and durations to improve its adhesion and electrical properties. The coating’s performance was evaluated by creating an eight-finger interdigitated sensor using a Voltera PCB printer. The sensor demonstrates exceptional performance when exposed to various loading and unloading pressures within the 0.2–500.0 kPa range. The results show a consistent correlation between the change in electrical resistance and the stress caused by the applied load. The ink is biodegradable in marine environments, which helps avoiding its accumulation in the ecosystem over time.

Supertoughened Polylactic Acid/Polybutylene Adipate Terephthalate Blends Compatibilized with Ethylene-Methyl Acrylate-Glycidyl Methacrylate: Morphology and Mechanical Properties by the Response Surface Methodology.

Optimized extrusion melt-blending of polylactic acid (PLA) polymer with a minor biopolymeric phase, polybutylene adipate terephthalate (PBAT), and compatibilized with random ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMA-GMA, Trademark: Lotader AX-8900) led to an outstanding improvement in mechanical properties. At the noncompatibilized PLA-PBAT (80-20) blend point, significant enhancement (∼4500%) in toughness and elongation-at-break was already obtained without compromising any elastic properties. The effect of the compatibilizer content on the mechanical properties of the PLA-PBAT (80-20) blend was investigated by an optimal custom response surface methodology. Thus, 2 wt % Lotader content was determined to be optimal by a numerical optimization methodology with a desirability value, D, of 0.882 to maximize toughness and elongation-at-break. The compatibilization and thermal behavior of the Lotader-modified blends were analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Upon adding the compatibilizer, the original phase-separated morphology of the blends changed from PBAT quasi-spherical domains to nearly elongated elliptical ones. It was also found that the interfacial boundary line of the domains faded away, which revealed that interfacial compatibility was achieved. The thermostability of the blends remained largely unaltered following the incorporation of PBAT and Lotader. Moreover, while PBAT exhibited a minor influence on the crystallinity of PLA, Lotader had no discernible impact on crystallinity, as evidenced by the DSC thermograms. Thus, the compatibilizer at the optimal point in the optimized blend ratio led to the formation of a phase-separated morphology that combined internal cavitation, interfacial cavitation, and strong adhesion features at the right proportions in the microstructure which underlies the micromechanisms driving the remarkable enhancement of as much as 7100% in toughness and ductility.

Effect of poly(lactic acid) molecular weight and composition on the morphology and crystallization behavior of polyhydroxybutyrate/poly(lactic acid) blends

Effect of poly(lactic acid) molecular weight and composition on the morphology and crystallization behavior of polyhydroxybutyrate/poly(lactic acid) blends

Growth of molecular orientation during post‐process annealing of poly(lactic acid) containing a fibrous nucleating agent

Growth of molecular orientation during post‐process annealing of poly(lactic acid) containing a fibrous nucleating agent

A short banana fiber—PLA filament for 3D printing: Development and characterization

AbstractThis study aims to develop a 3D printable composite filament using short banana fiber and polylactic acid (PLA). The filament was acquired through a single screw extruder, employing various blending techniques. Various fiber loadings were examined, impacting PLA's mechanical, thermal, and printability properties. The results revealed altered mechanical characteristics, with reduced tensile and flexural properties compared with pure PLA. However, these values are at an acceptable level for non‐structural applications. Compared with previous works, the filament developed in the present work is found out to be second strongest among the cellulose fiber‐reinforced PLA filaments. 3D printing with the composite filament encountered no significant issues. A modified mixing method improved mechanical characteristics, although 3D‐printed samples showed deteriorated mechanical characteristics due to poor interfacial bonding. This research introduces an environmentally viable strategy for advancing 3D printing technology by integrating banana fibers into PLA filament. The proposed strategy can be effectively utilized in making cellulose/PLA filaments for 3D printing applications. This innovative approach preserves PLA's natural biodegradability while carefully managing the integration of banana fibers and their potential effects on mechanical properties.Highlights Fiber loading influences mechanical, with minimal impact on thermal properties. Solution casting improved fiber/matrix bonding and filler homogeneity. Plasticizing effect reduces the tensile strength. Modified mixing resulted in even filament diameter and improved tensile properties.

Experimental investigations of temperature-sensitive shape memory polymer composites for 4D printing

Shape memory polymers (SMPs) and their composites (SMPCs) have emerged as popular materials in a variety of industries due to their unique properties of shape-changing behavior in response to external stimuli. The inclusion of reinforcement may modify the SMPs to enhance their thermal and shape memory properties. Different types of bio ceramics have already been used to alter the thermal and shape memory behavior of SMPs. However, using bioactive glass (BG) as filler to modify these properties has not yet been explored. Despite the significant advantages that shape-memory polymers (SMPs) offer when combined with 3D/4D printing technology, their potential in 3D printing has been explored only to a limited extent. This work created a solvent-based 4D-printed temperature-sensitive shape memory polymer composites (SMPCs) system using polylactic acid (PLA) and bioactive glass (BG). The influence of BG on the thermal as well as shape-memory capabilities of composites was further examined. An increase in the degree of crystallinity and viscoelastic characteristics of PLA/BG composites led to improved shape memory properties, like shape fixity and shape recovery. These findings suggest the potential for using the developed SMPC printed through 4D printing technology, to develop complex shapes for self-foldable structures and smart biomedical devices in the future.

Machine learning investigation of polylactic acid bead foam extrusion

AbstractThis study employs machine learning algorithms to analyze the bead foam extrusion process and to assess the impact of processing parameters, specifically focusing on their effects on bead foam density and melt pressure in under water granulation (UWG) for polylactic acid (PLA). These interrelated parameters, influenced by processing parameters such as temperature, screw speed, and blowing agent, possess challenges for traditional empirical methods to capture. The key factors that significantly impact the prediction of melt pressure in UWG are blowing agent, injector pressure, temperature in B‐extruder and die size. Likewise, essential parameters for predicting bead foam density comprise blowing agent, injector pressure, temperature in B‐extruder, die plate temperature, melt temperature in B‐extruder, and melt pressure in B‐extruder. Machine learning (ML) models were employed to forecast bead foam density and melt pressure in UWG using various processing parameters in PLA bead foam extrusion. The random forest model achieved a high coefficient of determination score of 0.96 for predicting melt pressure in UWG. Additionally, the decision tree model demonstrated effective predictions for bead density, with the score: 0.81. These ML models can be applied to diverse materials, leading to more sustainable, efficient processes for bead foam extrusion.

Performance of bioresorbable peptide incorporated polymers produced for fused deposition modelling (FDM)

The use of biomaterials in additive manufacturing (AM) of medical devices has gained significant attention over the years, especially in areas such as wound care and orthopedics. This study aims to investigate the performance of bioresorbable peptide-incorporated polymers produced for fused deposition modelling (FDM) process. Herein, we report FDM 3D Printing process of bioactive polymers comprising polycaprolactone (PCL), poly(lactic-co-glycolic acid) (PLGA) or polylactic acid (PLA) or blended with peptide–containing brush copolymers bearing similar synthetic polymer side chains. Mechanical, thermal and rheological properties of the materials were carried out and we report that the incorporation of bioactive polymers into these biodegradable polymers does not result in significant changes to glass transition temperature, melt temperature, tensile properties of the base polymers. However, it was observed that flexural and rheological properties altered significantly. This study provides an insight into the thermomechanical performance of bioresorbable peptide-incorporated polymers for FDM utilization which allows for their use potential in medical device fabrication.

On the essential work of fracture of polylactic acid/thermoplastic polyurethane/halloysite

The goal of this work is to investigate the mechanical and fracture characteristics of polylactic acid (PLA)/thermoplastic polyurethane (TPU)/halloysite (HNT). HNT with three levels (0, 3, and 6 wt.%) and TPU with three levels (10, 20, and 30 wt.%) were used as variables. The investigation of tensile properties revealed contrasting effects of TPU and HNT levels. Increasing TPU content to 30 wt.% led to a decrease in strength and modulus by 36% and 42% in turn, however resulted in a remarkable 338% improvement in elongation at break. Conversely, the addition of 3 wt.% HNT enhanced both tensile strength and modulus, although it caused a reduction in elongation at break. The results concerning fracture properties showed by incorporating TPU up to 30 wt.% EWF ( w e) and non-EWF ( βw p) rose by 459% and 178%, respectively. Additionally, the inclusion of 3 wt.% HNT further elevated the EWF compared to the compound containing 10 wt.% TPU without HNT. Through optimization, the compound with 10 wt.% TPU and 3 wt.% HNT was shown to have the optimum strength, stiffness, and toughness balance.

Contribution of cellulose nanofibrils on the strengthening and toughening of neat and blended polylactide specimens; and the differences after 3D-printing

The main purpose of this study was to use “green materials” approach by investigating effects of only 1 wt% Cellulose Nanofibrils (CNF) on the strengthening and toughening of neat and blended polylactide (PLA) biopolymer matrix. For this purpose, first of all effects of CNF were investigated in PLA/CNF biocomposite specimens. After blending of PLA with 10 phr bio-based thermoplastic polyester (b-TPE) elastomer, effects of CNF were investigated also for this PLA/b-TPE/CNF ternary biocomposite specimens. Mechanical tests revealed that due to the efficient strengthening and toughening mechanisms, CNF increased flexural strength of PLA by 33%, while b-TPE increased fracture toughness of PLA by 104%. When CNF and b-TPE were incorporated together, synergism in the strength and toughness values were occurred. All bioblend and biocomposite specimens were produced by using the same “melt mixing” technique in a laboratory size twin-screw extruder, and their test specimens were shaped by conventional “compression molding”. Since shaping by “3D-printing” is frequently used in the biomedical sectors, another distinctive aim of this study was to reveal whether there were any differences in the strength and toughness values of specimens after their 3D-printing. It was observed that due to the “textured” structure of 3D-printed specimens, their flexural strength values were approximately 20% lower, while fracture toughness values were approximately 20% higher.

A new nano-sachet manufactured by solution blow spinning to retard ripening of bananas using biodegradable nanostructured polymeric mats emitting 1-methylcyclopropene

The aim of this study was to produce nanostructured poly (lactic acid) (PLA) mats incorporated with the 1-MCP/α-CD complex (F1-MCP) by the solution blow spinning (SBS) technique and to apply them as a nano-sachet emitting 1-MCP in a banana packaging system. The nanofibers that comprise the mats presented uniform morphology with diameters between 157 and 184 nm. Scanning electron microscopy showed that crystals of 1-MCP/α-CD were encapsulated and found on the nanofibers' surface, changing their thermal properties and contact angles. The release of 1-MCP gas from the nano-sachet of nanostructured PLA mats with encapsulated 1-MCP/α-CD was proven based on the delay of banana ripening during storage (21 °C and 90 % RH). Therefore, the nanostructured PLA mats with encapsulated MCP/α-CD, produced by SBS, proved viable and applicable in packaging systems that aim to delay ripening and increase the postharvest shelf life of climacteric fruit, such as bananas.

3D-printed scaffolds for tissue engineering applications using thermosensitive hydrogels based on biopolymer blends

AbstractThree-dimensional (3D) printing is an emerging technology for the construction of complex 3D constructs used for tissue engineering applications. In this study, we are proposing the preparation of 3D printing hydrogel inks consisting of the synthetic polymers poly(caprolactone) and poly(lactic acid), the biopolymer chitosan, and naturally derived gelatin. In addition, pluronic F-127 was used to improve the miscibility between the hydrophobic and hydrophilic components due to its amphiphilic character, as well as for its good 3D printability. The printability of the hydrogel inks was optimized by varying the composition, the extrusion nozzle, and the temperature, while the integrity of the 3D scaffolds was secured via sol–gel transition. The produced hydrogels with PCL-pluronic-chitosan-gelatin/15-20-4-2 wt% (PC3.75-Pl5-CG) and PLA-pluronic-chitosan-gelatin/10-20-4-2 wt% (PL2.5-Pl5-CG) presented the best printability, producing smooth and uniform porous scaffolds. The prepared hydrogels were formed via the interactions between the polymers through hydrogen bonding. Additionally, the produced hydrogels exhibited temperature-dependent swelling behavior, and the scaffolds with PCL presented lower swelling capacity than the scaffolds with PLA. The produced scaffolds presented slower hydrolyzation rate in simulated body fluid (SBF) at 25 °C compared to 37 °C. Biological studies proved that the 3D-printed porous scaffolds were non-cytotoxic and promoted human adipose-derived mesenchymal stem cell adhesion. Graphical abstract

Recent advancements in bio-based dielectric and piezoelectric polymers and their biomedical applications.

The advent of polymer-based dielectrics marked a significant breakthrough in dielectric materials. However, despite their many advantages, they pose serious environmental threats. Therefore, in recent years, there has been growing interest in bio-based polymers as a sustainable alternative to traditional petroleum-based polymers. Their renewable nature and reduced environmental impact can fulfil the rising demand for eco-friendly substitutes. Beyond their ecological benefits, bio-based polymers also possess distinctive electrical properties that make them extremely attractive in a variety of applications. Considering these, herein, we present recent advancements in bio-based dielectric polymers and nanocomposites. First, the fundamental concepts of dielectric and polymer-based dielectric materials are covered. Then, we will delve into the discussion of recent advancements in the dielectric properties and thermal stability of bio-based polymers, including polylactic acid, polyhydroxyalkanoates, polybutylene succinate, starch, cellulose, chitosan, chitins, and alginates, and their nanocomposites. Other novel bio-based dielectric polymers and their distinct dielectric characteristics have also been pointed out. In an additional section, the piezoelectric properties of these polymers and their recent biomedical applications have been highlighted and discussed thoroughly. In conclusion, this paper thoroughly discusses the recent advances in bio-based dielectric polymers and their potential to revolutionize the biomedical industry while cultivating a more sustainable and greener future.

Experimental study on the effect of filament-extrusion rate on the structural, mechanical and thermal properties of material extrusion 3D-printed polylactic acid (PLA) products

AbstractMaterial extrusion (MEX), also commonly referred to as fused deposition modeling (FDM) or fused filament fabrication (FFF) is currently one of the most commonly used additive manufacturing techniques. The quality of the 3D-printed objects fabricated by MEX methods highly relies on various printing parameters, one of which is the so-called filament extrusion multiplier (k). In this study, 3D-printed parts were prepared by MEX technique during which the material feeding rate was adjusted by varying the extrusion multiplier in the range of 97–105% (k = 0.97–1.05). The fabricated parts were tested for their geometrical, structural, mechanical, and thermal conductivity properties. Based on computed tomographic analysis and scanning electron microscopic images, increasing the k parameter resulted in smaller voids, along with gradually decreasing porosity (from 5.82 to 0.05%). Parallel to the decreasing defects, the thermal conductivity of the parts improved from 0.157 to 0.188 W/mK as determined by light-flash analysis technique. On the other hand, when k was set to ≥ 1.03 the geometrical accuracy declined, the size of the specimens considerably increased relative to the nominal values, especially in the X–Y directions due to excess material getting “squeezed” on the sides of the specimens. This latter phenomenon also resulted in the formation of a number of stress concentration sites, which manifested in the decrease of mechanical properties. Accordingly, the tensile, flexural, and impact strength of the samples improved up to k = 1.03; however, above that it dropped considerably.

Mechanical recycling of poly(lactic acid)/agave fiber biocomposites

This paper focuses on evaluating the mechanical recycling potential of poly(lactic acid) (PLA) biocomposites reinforced with agave fibers (AF). The biocomposites were prepared by extrusion using 5, 15, and 30 wt.% of agave fibers and reprocessed up to eight times. The results show that the fiber dimensions substantially decrease during reprocessing, especially after the first extrusion cycle, followed by a more gradual decrease in each subsequent cycle. The melt flow index (MFI) and the mechanical properties (except impact strength) tend to decrease as the fiber concentration increases. On the other hand, the glass transition temperature ( T g) and the crystallinity ( X c) of the biocomposites increased with increasing fiber concentration. It is important to highlight that closed-loop reprocessing does not significantly affect the overall behavior of the biocomposites under the conditions investigated. Therefore, PLA reinforced with AF is suitable for primary recycling since the final properties are mainly influenced by the fiber concentration and less by the number of reprocessing cycles.

Glycine/alginate-based piezoelectric film consisting of a single, monolithic β-glycine spherulite towards flexible and biodegradable force sensor

Abstract Development of piezoelectric biomaterials with high piezoelectric performance, while possessing excellent flexibility, biocompatibility, and biodegradability still remains a great challenge. Herein, a flexible, biocompatible and biodegradable piezoelectric β-glycine-alginate-glycerol (Gly-Alg-Glycerol) film with excellent in vitro and in vivo sensing performance was developed. Remarkably, a single, monolithic β-glycine spherulite, instead of more commonly observed multiple spherulites, was formed in alginate matrix, thereby resulting in outstanding piezoelectric property, including high piezoelectric constant (7.2 pC/N) and high piezoelectric sensitivity (1.97 mV/kPa). The Gly-Alg-Glycerol film exhibited superior flexibility, enabling complex shape-shifting, e.g. origami pigeon, 40% tensile strain, and repeated bending and folding deformation without fracture. In vitro, the flexible Gly-Alg-Glycerol film sensor could detect subtle pulse signal, sound wave, and recognize shear stress applied from different directions. In addition, we have demonstrated that the Gly-Alg-Glycerol film sensor sealed by polylactic acid and beeswax could serve as an in vivo sensor to monitor physiological pressure signals such as heartbeat, respiration, and muscle movement. Finally, the Gly-Alg-Glycerol film possessed good biocompatibility, supporting the attachment and proliferation of rat mesenchymal stromal cells, and biodegradability, thereby showing great potential as biodegradable piezoelectric biomaterials for biomedical sensing applications.

Modifying the Backbone Chemistry of PEG-based Bottlebrush Block Copolymers for the Formation of Long-Circulating Nanoparticles.

Nanoparticle physicochemical properties have received great attention in optimizing the performance of nanoparticles for biomedical applications. For example, surface functionalization with small molecules or linear hydrophilic polymers is commonly used to tune the interaction of nanoparticles with proteins and cells. However, it is challenging to control the location of functional groups within the shell for conventional nanoparticles. Nanoparticle surfaces composed of shape-persistent bottlebrush polymers allow hierarchical control over the nanoparticle shell but the effect of the bottlebrush backbone on biological interactions is still unknown. We report the synthesis of novel heterobifunctional poly(ethylene glycol) (PEG)-norbornene macromonomers modified with various small molecules to form bottlebrush polymers with different backbone chemistries. We demonstrate that micellar nanoparticles composed of poly(lactic acid) (PLA)-PEG bottlebrush block copolymer (BBCP) with neutral and cationic backbone modifications exhibit significantly reduced cellular uptake compared to conventional unmodified BBCPs. Furthermore, the nanoparticles display long blood circulation half-lives of ∼22h and enhanced tumor accumulation in mice. Overall, our work sheds light on the importance of the bottlebrush polymer backbone and provides a strategy to improve the performance of nanoparticles in biomedical applications. This article is protected by copyright. All rights reserved.

Green Synthesis and Characterization of Silver Anchored ZnO Nanoparticle as the Antimicrobial Reinforcement for Polylactide (PLA) Films

AbstractThe aqueous extract of endophytic fungi (Periconia sp.) was effectively used as a reducing agent to anchor Ag nanoparticles on the ZnO surface. The XRD, UV‐Vis, SEM‐EDX and TEM analyses were performed to ensure the formation of AgNP@ZnO architecture. TEM analysis confirmed that the 4‐20 nm sized Ag nanoparticles were anchored evenly on the surface of ZnO with 16‐78 nm in size. The antimicrobial study showed the superior performance of AgNP@ZnO functional nanoparticles than the pristine ZnO against pathogenic bacteria Staphylococcus aureus (gram‐positive) and Escherichia coli (gram‐negative). Hence, AgNP@ZnO functional particles were effectively explored as antimicrobial reinforcement for fabricating composite films using polylactic acid (PLA) as a matrix. The obtained nanocomposite films showed excellent antibacterial activity, which increases with increasing AgNP@ZnO loading.This article is protected by copyright. All rights reserved.

Synergistic flame retardancy of aluminum diethylphosphinate and piperazine pyrophosphate/β‐cyclodextrin in polylactic acid

AbstractPolylactic acid has good biodegradability and processability, but its flammability and serious droplet characteristics limit its development and application. Therefore, developing safer flame‐retardant PLA materials is crucial. This research develops a novel flame‐retardant polylactic acid (PLA) material blend, utilizing aluminum diethylphosphinate (AlPi), piperazine pyrophosphate (PAPP), and β‐cyclodextrin. Optimal synergy occurs at a 5:1 PAPP/β‐CD mass ratio with 4 wt.% AlPi. This combination significantly reduces the heat release peak from 294.89 to 144.21 kW·m−2 and generates non‐combustible residues. The sample forms a stable, uniform carbon layer during combustion due to hydrogen bond crosslinking and Lewis acid–base reactions. The activation energy (Eα) is raised from 264.99 to 281.08 kJ·mol−1 between 312 and 402°C. Thus, an AlPi‐PAPP‐β‐CD based P‐C‐N composite flame retardant is investigated, offering a promising research direction for developing fire‐safe polylactic acid materials. This research may yield valuable insights for diverse applications.