Polylactic Acid Structures Research Articles

Tannic acid-grafted Polylactic acid films: A nonmigrating antibacterial packaging for chilled fresh meat

Antimicrobial packaging can prolong the shelf life of fresh food, but those active antimicrobial substances may leach into the food and affect its quality. To avoid this phenome, the CC double bond was first incorporated into the chemical structure of polylactic acid (PLLA) and tannic acid (TA) to prepare poly(L-LA-co-butyrate itaconate) (PLBI) and photoactive tannic acid (pTA). Then pTA-grafted PLBI (pTA-g-PLBI) films were fabricated using UV curing technology. Results showed that pTA was successfully grafted onto the surface of PLBI film and formed a uniform layer. The pTA-g-PLBI films exhibited good bacteriostatic effects of 86 %, 90 %, and 96 % on E. coli, P. fluorescens, and S. aureus, respectively. Additionally, pTA-g-PLBI packaging reduced the relative abundance of Shewanella, Psychrobacter, and Pseudomonas in chilled pork and delayed the deterioration of pork for more than 5 days.

Accelerated aging behavior of degradable and non-degradable microplastics via advanced oxidation and their adsorption characteristics towards tetracycline

The increasing global utilization of biodegradable plastics due to stringent regulations on traditional plastics has caused a significant rise in microplastic (MPs) pollution in aquatic ecosystems from biodegradable products. However, the environmental behavior of biodegradable MPs remains inadequately elucidated. This study explored the aging processes of polylactic acid (PLA) and polystyrene (PS) under a heat-activated potassium persulfate (K2S2O8) system, as well as their adsorption characteristics towards tetracycline (TCs). In comparison to PS, the surface structure of PLA experienced more pronounced changes over aging, exhibiting evident pits, cracks, and fragmentation. The carbonyl index (CI) and oxygen/carbon ratio (O/C) of PS displayed exponential growth over time, whereas the values for PLA showed linear and exponential increases, respectively. The adsorption capacity of TCs by PS and PLA aged for 6 days increased from 0.312 mg‧g−1 and 0.457 mg‧g−1for original PS and PLA, respectively, to 0.372 mg‧g−1 and 0.649 mg‧g−1. Meanwhile, the adsorption rate (k2 values) for TCs decreased by 42.03 % for PS and 79.64 % for PLA compared to their initial values. The findings indicated that biodegradable PLA-MPs may exhibit higher tetracycline carrying capacities than PS, potentially increasing environmental and organismal risks, particularly in view of aging effects.

DESIGN AND STRUCTURAL ANALYSIS OF 3D-PRINTED POROUS POLYLACTIC ACID/HYDROXYAPATITE SCAFFOLDS

Different designs of three-dimensional (3D) structures have gained increasingly significant in bone tissue engineering. For scaffolds, having appropriate porosity and adequate mechanical properties is crucial. The porosity and mechanical properties of scaffolds are higly influenced by their 3D modeled design. By evaluating the mechanical properties of scaffolds with various designs, it can be confirmed that they could serve as an important platform for the regeneration of damaged bone tissue. In this study, a diverse range of unit cells and lattice structures featuring different pore structures of polylactic acid (PLA)/hydroxyapatite (HA) based scaffolds were modeled and designed. Structural analyses of the designed models were conducted in a simulation environment and their mechanical properties were compared with similar studies. The results suggest that PLA/HA-based scaffolds with different designs hold high potential for applications in bone tissue engineering.

Molecular structure regulation of functional polylactic acid based on chain expansion reaction and its improved hydrolysis resistance

AbstractIn this work, the functional polylactic acid (PLA) was synthesized using epoxy chain extender (ADR) as a chain extender agent through melt blending method. The effects of ADR content on the molecular structure, thermal properties, and tensile properties of the functional PLA were investigated. Meanwhile, the hydrolytic behavior of the PLA/ADR materials at different hydrolysis temperatures was explored. It was found that ADR effectively regulated the molecular structure of PLA in the molten state and significantly increased the relative molecular weight, storage modulus, and complex viscosity of PLA. In addition, the Cole‐Cole diagram results suggested the branched structure of PLA chain expansion systems. Based on mechanical property tests, it was noted that the addition of ADR made the molecular chain form a micro‐crosslinked structure. Additionally, the mass loss rate of PLA/1.6ADR (the dosage of ADR was 1.6 wt%) was 14.75% after 14 weeks of hydrolysis under hydrolysis conditions at 58°C, while that of pure PLA was 25.89%. Moreover, the functional PLA/ADR materials exhibited significantly slower decrease rates in molecular weight, melting temperature, and tensile strength, and still maintained intact morphology after 14 weeks of hydrolysis compared to pure PLA. Therefore, the molecular structure of PLA is effectively regulated by ADR, which greatly enhances the hydrolysis resistance and further promotes the range of application of PLA.

A study of polylactic Acid/K2SiF6:Mn4+ composite luminescent materials: design, preparation, and properties

K2SiF6:Mn4+ (KSF) has been the most representative red emitting fluoride phosphors thanks to its cheap production cost and excellent luminescence properties. Nevertheless, the photoluminescent properties of this phosphor are limited due to intrinsically poor water resistance. In this work, constructing composite luminescent materials by blending KSF with polylactic acid (PLA) polymer was developed using the melt mixing process. The tactic not only makes full use of the photoluminescent properties of KSF, but also enhances the moisture resistance ability by alleviating or suppressing hydrolysis. The photoluminescent spectra, temperature-dependence emitting spectra, scanning electron microscopy, thermogravimetric analysis, and wide-angle x-ray scattering were conducted to study the morphology, thermal stability and photoluminescent properties of the KSF@PLA composite luminescent materials. KSF was evenly distributed in PLA. Furthermore, the influence of the doping amount of KSF on the structure and properties of PLA was systematically studied and the optimal doping amount of KSF in PLA was determined to be 10%, marked as KSF@PLA 3. Finally, KSF@PLA 3 exhibited excellent moisture resistance ability and thermal stability. After soaking in deionized water for 7 days, the emission intensity of KSF@PLA 3 is almost consistent with the original emission intensity.

Effect of the interchain interaction on the crystallization kinetics and crystal structure of polylactic acid under nitrogen

In order to prepare polylactic acid (PLA) foam material with excellent performance by utilizing nitrogen (N2), the crystallization behavior of PLA under N2 has been studied.

Biodegradable 3D printed polylactic acid structures for different engineering applications: effect of infill pattern and density

Biodegradable 3D printed polylactic acid structures for different engineering applications: effect of infill pattern and density

3D-printed polylactic acid-microencapsulated phase change material composites for building thermal management

The integration of phase change materials (PCM) into architectural elements is an emerging strategy to enhance thermal energy storage in modern buildings. This research examines 3D-printed polylactic acid structures incorporated with microencapsulated PCM, targeting a more efficient thermoregulation in foundational architectural sections such as walls, floors, and ceilings. Through rigorous evaluations, the polylactic acid-PCM composite revealed promising thermoregulatory properties. Notably, latent heat values stood at 198.4 J/g for melting and 197.9 J/g for freezing. Real-world experiments demonstrated a distinct advantage, maintaining temperatures 3.2°C–3.3 °C higher than standard polylactic acid at night and exhibiting a cooler range of 10.4 °C–13.3 °C during daylight. Within specific geographical contexts, like the Mediterranean and Aegean Seas coastline, 0.026 m thick polylactic acid-PCM panels stood out, registering 100 % energy savings. The findings consistently showed that an increase in panel thickness correlated with a decrease in building heating needs. Further analysis explored the carbon emissions landscape. Coal, when utilized with 0.05 m-thick polylactic acid-PCM panels, was identified as particularly effective, yielding a reduction of 34 kg/m2 in annual CO2 emissions. Collectively, the findings underscore the transformative potential of polylactic acid-PCM composites, positioning them as pivotal tools for advancing architectural energy efficiency and fostering sustainable building innovations.

Combustion Performance of Various Polylactic Acid Plastics with Different Porous Structures Constructed by 3D Printing

Polylactic acid (PLA) has intrigued widespread attention as a biodegradable and environmentally friendly polymer, and recent research has revealed that the use of porous PLA in heat sinks for thermal management materials offers promising development potential. However, the heat transfer performance is closely related to its structure theoretically, whether it is virgin, and how the pore structure affects its heat transfer. Therefore, a novel approach is proposed to address this issue by preparing porous PLA through 3D printing at low complexity and cost, the combustion performance is employed to evaluate the heat transfer indirectly, and the higher burning speed represents higher efficient heat transfer. A new framework is developed to investigate combustion performance and three series of PLA with different pore structures in pore shape, size, and interval are studied by combining experimental tests, respectively. It demonstrates that adjusting the pore structure of PLA significantly alters its combustion performance, evidenced by significant variations in flame growth index, which are 83% better for the 2 mm holes than the largest holes and 71% better for the 2 mm interval than for the sparsest pore structure. Generally, it provides some experimental basis for designing porous thermal management materials; the various pore structures generate different combustion performances, corresponding to various heat transfer.

Analysis of Structure and Functional Group of Filament Product-Based PLA/Nanographite Nanocomposite

In many polymer compounds, Polylactic Acid (PLA) is a polyalcohol material that has the most potential material which is potent for biological degradation. They have been applied as filaments in additive manufacturing. The PLA properties can be modified by adding nanomaterials such as graphite nanoplatelets. This study aims to obtain the characteristics of PLA-based filament nanocomposite with nanographite reinforcement. Methods include exploration research to obtain nanocomposite filament with PLA and 1% of nanographite. The mixing process of nanographite in PLA solution with chloroform solvent and then the extrusion process of nanocomposite using a single extruder. The product comparison before and after the extrusion process was analyzed using X-ray diffraction and Fourier Transform infrared. Diffractogram results indicate that the original PLA structure is amorphous, and after mixing using nanographite, peaks of nanographite appeared clearly. After the extrusion process, some peaks at 16.7° and 19.1° disappeared, but only a peak 26.6° appeared in the diffractogram. Extrusion makes the structure change. Functional group analysis confirms that some reactions occurred so that many peaks were removed, and several new peaks were observed. It indicates that the extrusion process of PLA/nanographite results in different structures and functional groups that indicate a change in its properties.

Effect of epoxy chain extenders on molecular structure and properties of polylactic acid

AbstractIn this work, a novel functional polylactic acid (PLA) was prepared by melt blending using epoxy Joncryl ADR 4468 (ADR) as chain extender. The effects of the epoxy chain expander ADR on the molecular structure, crystallization properties, rheological properties, and mechanical properties of PLA were studied. Furthermore, the chain expansion mechanism was analyzed. It was found that the epoxy group of the epoxy chain extender reacted with the terminal hydroxyl and terminal carboxyl groups of PLA in the molten state, thus significantly increasing the molecular weight of PLA. Meanwhile, the weight average molecular weight of PLA increased by 42.51% when the maximum additional amount of epoxy chain extender was 1.2 wt%. The dynamic rheological experiments also confirmed that ADR can effectively improve the storage modulus, loss modulus and complex viscosity of PLA systems and the Cole‐Cole diagram reveals the branched structure of PLA chain expansion systems. The formation of this branched structure will destroy the regularity of the PLA chain, reduce the crystallization capacity of PLA, and increase the cold crystallization temperature of the PLA system. Through SEM and mechanical property tests, it is found that the addition of ADR makes the molecular chain form a micro‐crosslinked structure, thereby improving the tensile strength of PLA. Therefore, the molecular structure of PLA was effectively regulated and exhibited a promising performance, which greatly expands the potential applications of PLA.

Synthesis, Modification and Application of Polylactic Acid

The massive use of petroleum-based plastics has caused tremendous damage to the world's environment, so it has become increasingly urgent to develop biodegradable materials represented like polylactic acid (PLA). PLA is a non-polluting, completely degradable and renewable polymer material with high strength, high modulus and good biocompatibility. However, the disadvantages of conventional PLA, such as poor heat resistance and limited flexibility, limit its application. Therefore, its modification is needed. This article summarizes the structure and properties of PLA and describes the synthesis methods based on direct polymerization, ring-opening polymerization and enzyme-catalyzed polymerization. The article also reviews the methods of PLA modification, including physical modification by adding fibrous materials, nucleating agents, and compound modification, and chemical methods such as copolymerization and cross-graft modification. Moreover, the article presents the applications of PLA in packaging and medical materials. At the end of this article, future research and development directions of PLA are discussed.

Evaluation of the Antioxidant and Antimicrobial Potential of SiO2 Modified with Cinnamon Essential Oil (Cinnamomum Verum) for Its Use as a Nanofiller in Active Packaging PLA Films.

One of the main causes of food spoilage is the lipid oxidation of its components, which generates the loss of nutrients and color, together with the invasion of pathogenic microorganisms. In order to minimize these effects, active packaging has played an important role in preservation in recent years. Therefore, in the present study, an active packaging film was developed using polylactic acid (PLA) and silicon dioxide (SiO2) nanoparticles (NPs) (0.1% w/w) chemically modified with cinnamon essential oil (CEO). For the modification of the NPs, two methods (M1 and M2) were tested, and their effects on the chemical, mechanical, and physical properties of the polymer matrix were evaluated. The results showed that CEO conferred to SiO2 NPs had a high percentage of 2,2-diphenyl-l-picrylhydrazyl (DPPH) free radical inhibition (>70%), cell viability (>80%), and strong inhibition to E. coli, at 45 and 11 µg/mL for M1 and M2, respectively, and thermal stability. Films were prepared with these NPs, and characterizations and evaluations on apple storage were performed for 21 days. The results show that the films with pristine SiO2 improved tensile strength (28.06 MPa), as well as Young's modulus (0.368 MPa) since PLA films only presented values of 27.06 MPa and 0.324 MPa, respectively; however, films with modified NPs decreased tensile strength values (26.22 and 25.13 MPa), but increased elongation at break (from 5.05% to 10.32-8.32%). The water solubility decreased from 15% to 6-8% for the films with NPs, as well as the contact angle, from 90.21° to 73° for the M2 film. The water vapor permeability increased for the M2 film, presenting a value of 9.50 × 10-8 g Pa-1 h-1 m-2. FTIR analysis indicated that the addition of NPs with and without CEO did not modify the molecular structure of pure PLA; however, DSC analysis indicated that the crystallinity of the films was improved. The packaging prepared with M1 (without Tween 80) showed good results at the end of storage: lower values in color difference (5.59), organic acid degradation (0.042), weight loss (24.24%), and pH (4.02), making CEO-SiO2 a good component to produce active packaging.

Mapping internal strain fields of fused filament fabrication metal filled polylactic acid structure using digital volume correlation.

With the advancement in Fused Filament Fabrication (FFF), its application is increasing widely across different industries such as aeronautical, biomedical, robotics, etc. The internal structure is becoming more complex and intricate with varying materials of reinforcement which are used to improve mechanical properties. Current measurement techniques like Digital Image Correlation (DIC) are non-destructive testing methods that do not provide enough information on the behaviour of internal microstructure for anisotropic FFF materials. Digital Volume Correlation (DVC) is non-destructive testing technique which provides full field internal 3D deformation and strain fields. Copper particle filled PLA samples manufactured using FFF method with 20, 40, 60 and 80 infill percentages were loaded in tension inside Micro-CT. X-rays were passed through the sample to get a volumetric dataset for different loadings. Using DVC method on the dataset, internal displacement and strain fields were generated for 20, 40, 60 and 80 infill percentage FFF sample.

Mechanical performance and microscopic characterization of additively manufactured functionally graded material (WPC/Ceramic-PLA) via fused deposition modelling

During fabrication of complex polymeric structure engineers need to compromise either accuracy or duration which hinders the production efficiency of the industries. Additive manufacturing is an evolving technology with great potential to achieve enhanced mechanical properties of materials over other manufacturing processes. Additive manufacturing effectively reduces lead time thus providing faster fabrication. A prevalent additive manufacturing method to fabricate polymeric structure is fused deposition modelling. Composite material generally possesses better mechanical properties than non-composite material. Polylactic acid is one of popular feedstocks used to fabricate components through fused deposition modelling. Functionally graded materials are structured to possess different mechanical properties towards a graded direction. Hence, this study aims to provide insight to the characteristics of the functionally graded materials structure fabricated with wood polymer composite and ceramic-reinforced polylactic acid. Mechanical tests such as tensile (smooth and V-notch), compression, flexural, impact, and hardness (Shore D hardness) are conducted for functionally graded materials structure and the extracted results are compared with the characteristics of wood polymer composite and ceramic-reinforced polylactic acid materials. The tensile strength of the functionally graded materials structure is found superior to weaker composites (wood polymer composite) and comparable to resilient materials (ceramic-reinforced polylactic acid). Microscopical examinations are carried out for the fabricated structure to ensure the quality. The fractured surfaces are examined using optical microscope to evaluate the mode of failures. The microscopic evaluation conducted for fabricated and fractured structure indicates robust bonding within and between (functionally graded materials interface) wood polymer composite and ceramic-reinforced polylactic acid structure.

Prediction of Mechanical Properties for Carbon fiber/PLA Composite Lattice Structures Using Mathematical and ANFIS Models.

This study investigates the influence of design, relative density (RD), and carbon fiber (CF) incorporation parameters on mechanical characteristics, including compressive modulus (E), strength, and specific energy absorption (SEA) of triply periodic minimum surface (TPMS) lattice structures. The TPMS lattices were 3D-printed by fused filament fabrication (FFF) using polylactic acid (PLA) and carbon fiber-reinforced PLA(CFRPLA). The mechanical properties of the TPMS lattice structures were evaluated under uniaxial compression testing based on the design of experiments (DOE) approach, namely, full factorial design. Prediction modeling was conducted and compared using mathematical and intelligent modeling, namely, adaptive neuro-fuzzy inference systems (ANFIS). ANFIS modeling allowed the 3D printing imperfections (e.g., RD variations) to be taken into account by considering the actual RDs instead of the designed ones, as in the case of mathematical modeling. In this regard, this was the first time the ANFIS modeling utilized the actual RDs. The desirability approach was applied for multi-objective optimization. The mechanical properties were found to be significantly influenced by cell type, cell size, CF incorporation, and RD, as well as their combination. The findings demonstrated a variation in the E (0.144 GPa to 0.549 GPa), compressive strength (4.583 MPa to 15.768 MPa), and SEA (3.759 J/g to 15.591 J/g) due to the effect of the studied variables. The ANFIS models outperformed mathematical models in predicting all mechanical characteristics, including E, strength, and SEA. For instance, the maximum absolute percent deviation was 7.61% for ANFIS prediction, while it was 21.11% for mathematical prediction. The accuracy of mathematical predictions is highly influenced by the degree of RD deviation: a higher deviation in RD indicates a lower accuracy of predictions. The findings of this study provide a prior prediction of the mechanical behavior of PLA and CFRPLA TPMS structures, as well as a better understanding of their potential and limitations.

Machine Learning and Regression Analysis Approaches for Investigation of Mechanical Properties of FDM Manufactured Re-Entrant Auxetic Structures Under Flexural Loading

This paper describes an experimental study on re-entrant auxetic structures manufactured by fused deposition modeling (FDM). The feedstock materials of NPR structures are acrylonitrile butadiene styrene (ABS) and poly-lactic acid (PLA). Experimental study is performed to examine the effect of design factors (angle, width, and length of arm) of unit cell of auxetic structures on three responses namely strength, stiffness, and specific energy absorption (SEA) under flexural loading. From the experimental results, it is found that flexural strength improves with increase in all three design factors of ABS structures; while it improves with increase in angle and reduction in width and length of arm for PLA structures. Furthermore, based on experimental study, regression models of responses are developed using analysis of variance (ANOVA). Also, machine learning (ML) models using neural networks are developed to predict all three responses. Results of regression models are compared with NN models to assess accuracy of prediction. Finally, optimal configuration of auxetic structure is determined using gray relational analysis (GRA) to improve the responses; and reduce weight and fabrication time.

FDM manufactured auxetic structures: An investigation of mechanical properties using machine learning techniques

The present article describes an experimental study on re-entrant auxetic structures manufactured by fused deposition modelling (FDM). The feedstock materials of NPR structures are acrylonitrile butadiene styrene (ABS) and poly-lactic acid (PLA). Experimental study is performed to examine the effect of design factors (angle, width, and length of arm) of unit cell of auxetic structures on three responses namely strength, stiffness and specific energy absorption (SEA) under flexural loading. From the experimental results, it is found that flexural strength improves with increase in all three design factors of ABS structures; while it improves with increase in angle, and reduction in width and length of arm for PLA structures. Further, based on experimental study regression models of responses are developed using analysis of variance (ANOVA). Also, machine learning (ML) models using neural networks are developed to predict all three responses. It is observed that, trained DNN models predicted strength, stiffness and SEA with deviation of 1.62%, 8.33%, and 5.37% for ABS material and 3.056%, 5.56%, and 2.25% for PLA material, compared to SNN models respectively. Further, results of regression models are compared with NN models to assess accuracy of prediction. Finally, optimal configuration of auxetic structure is determined using grey relational analysis (GRA) to improve the responses; and reduce weight and fabrication time.

3D printing of polylactic acid: recent advances and opportunities.

Bio-based polymers are a class of polymers made by living organisms, a few of them known and commercialized yet. Due to poor mechanical strength and economic constraints, they have not yet seen the extensive application. Instead, they have been an appropriate candidate for biological applications. Growing consumer knowledge of the environmental effect of polymers generated from petrochemical sources and a worldwide transition away from plastics with a lifespan of hundreds of years has resulted in greater interest in such hitherto unattainable sectors. Bio-based polymers come in various forms, including direct or "drop-in" replacements for their petrochemical counterparts with nearly identical properties or completely novel polymers that were previously unavailable, such as polylactide. Few of these bio-based polymers offer significantly improved technical specifications than their alternatives. Polylactic acid (PLA) has been well known in the last decade as a biodegradable thermoplastic source for use in 3DP by the "fused deposition modeling" method. The PLA market is anticipated to accomplish 5.2 billion US dollars in 2020 for its industrial usage. Conversely, 3DP is one of the emerging technologies with immense economic potential in numerous sectors where PLA is one of the critical options as the polymer source due to its environmentally friendly nature, glossiness, multicolor appearance, and ease of printing. The chemical structure, manufacturing techniques, standard features, and current market situation of PLA were examined in this study. This review looks at the process of 3DP that uses PLA filaments in extrusion-based 3DP technologies in particular. Several recent articles describing 3D-printed PLA items have been highlighted.

Review of mechanical properties and impact response of PLA auxetic structures

In this paper, mechanical properties under quasi-static loading conditions and low to high-velocity impact response of Poly-lactic acid (PLA) material produced by the Fused Deposition Modeling (FDM) 3D printing method, having auxetic and non-auxetic geometric structures are critically assessed. Specifically, the load–displacement curve under various loads and parameters, such as energy absorption and the existence of the NPR effect with varying applied loads, are investigated. The effect of a large collection of material parameters, process parameters, and geometrical effects on load–displacement curves, strength, stiffness, and energy absorption are discussed in detail. The in-depth studies on auxetic structures of PLA, for quasi-static compressive load and low to high-velocity impact load, have shown that its impact resistance is superior to that of its non-auxetic counterparts. Also, a method for predicting peak load and maximum displacement for low-velocity impact derived from quasi-static loading data is discussed.