Properties Of Polylactic Acid Research Articles

Innovative Approaches for Manufacturing Epoxy-Modified Wood and Cellulose Fiber Composites: A Comparison between Injection Molding and 3D Printing.

The current study focused on improving the properties of polylactic acid (PLA) for wider application in load-bearing scenarios. Various methods were explored to optimize the interaction between PLA and natural fibers, particularly wood fibers (WFs). Alkalized and epoxy-impregnated WFs were evaluated against untreated WFs and cellulose fibers in both injection molding (IM) and fused deposition modeling (FDM). FTIR analysis revealed the removal of hemicellulose and lignin in alkalized WFs and uniform epoxy curing. Addition of fibers reduced PLA's thermal stability while acting as nucleating agents. Additionally, fibers augmented the storage modulus of biocomposites, with alkalized fibers exhibiting the highest tensile modulus in IM. FDM samples with a 0° raster angle showed superior impact resistance compared to IM counterparts. Moreover, raster angle significantly influenced FDM biocomposite properties, enhancing the tensile strength and modulus of untreated WF and cellulose fibers at 0°. Although FDM did not produce alkalized WF samples, epoxy impregnation emerged as a promising method for enhancing PLA/WF composite mechanical properties in the IM process, offering valuable insights for composite material development.

Antiviral properties of polylactic acid and nano-TiO2 for 3D printing

Throughout history, viruses have consistently adapted to survive and spread. Understanding airborne transmission and surface survival emphasizes the necessity for antiviral materials. This study demonstrates virucidal reduction of human Coronavirus 229E and Feline Calicivirus on a polylactic acid and titanium dioxide nanoparticle composite with photocatalytic activity and UV activation. Mechanical properties and UV spectroscopy are also examined, suggesting the potential of the composite in medical and food applications through additive manufacturing.

Analysis of the effect of boric acid and compatibilizer addition to polylactic acid/basalt fiber composites

AbstractThe objective of this study is to improve the properties of polylactic acid (PLA), a biopolymer produced from renewable resources, without compromising its environmentally friendly “natural composite” properties. The aim was to expand the application range of PLA by making it suitable for the production of high performance composites. With this in mind, it was decided to use inorganic and environmentally friendly materials such as basalt fiber (BF) and boric acid (BA) as reinforcements. Adhesive wear and tensile tests were used to investigate the tribological and mechanical performance of the composites. Differential scanning calorimetry (DSC) and dimensional stability analysis (DSA) methods were used to investigate the thermal properties. Scanning electron microscopy analysis was also used to investigate the morphological properties of the samples. In addition, a matrix modification process using Joncryl®, an epoxy‐based chain extender chemical, was applied to enhance the interfacial interaction between the composite components and improve the composite properties by improving the dispersion of reinforcing materials. As a result of the characterization tests, it was observed that a significant improvement in the properties of the material type containing 10 wt% BF, 0.25 wt% BA and 2 wt% Joncryl® was achieved. A 19% increase in tensile strength of this type of material was observed compared with unreinforced PLA, while the sharp peak increase in the coefficient of friction (COF) curve was shifted from 20 m to 60 m. As a result, it has been presented that environmentally friendly and inorganic materials such as BF and BA can be used to produce composite materials that will serve sectors where the need and use of high performance materials is intense, especially in the automotive, aerospace and aviation sectors.Highlights The properties of PLA matrix composites were improved by the simultaneous use of BF and BA and the addition of Joncryl®. The structural properties of PLA, an environmentally friendly polymer, have been improved without compromising this characteristic. PLA matrix natural composites with performance that can be used in the automotive, aerospace and aviation sectors have been developed.

Temperature and strain rate-dependent compression properties of 3D-printed PLA: an experimental and modeling analysis

PurposeThis study aims to investigate the compression characteristics of the 3D-printed polylactic acid (PLA) samples at temperatures below the glass transition temperature (Tg) with varying strain rates and develop a thermo-mechanical viscoplastic constitutive model to predict the finite strain compression response using a single set of material parameters. Also, the micro-mechanical damage processes are linked to the global stress–strain response at varied strain rates and temperatures through scanning electron microscopy (SEM).Design/methodology/approachTg of PLA was determined using a dynamic mechanical analyzer. Compression experiments were conducted at strain rates of 2 × 10–3/s and 2 × 10–2/s at 25°C, 40°C and 50°C. The failure mechanisms were examined using SEM. A finite strain thermo-mechanical viscoplastic constitutive model was developed to analyze the deformations at the considered strain rates and temperatures.FindingsTg of PLA was determined as 55°C. While the yield and post-yield stresses drop with increasing temperature, their trend reverses with an increased strain rate. SEM imaging indicated plasticizing effects at higher temperatures, while filament fragmentation and twisting at higher strain rates were identified as the dominant failure mechanisms. Using a non-linear regression analysis to predict the experimental data, an overall R2 value of 0.98 was achieved between experimental and model prediction, implying the robustness of the model’s calibration.Originality/valueIn this study, a viscoplastic constitutive model was developed that considers the combined effect of temperature and strain rate for FDM-printed PLA experiencing extensive compression. Using appropriate temperature-dependent modulus and flow rate properties, a single set of model parameters predicted the rise in the gap between yield stress and degree of softening as strain rates and temperatures increased.

The Coloristic Properties of Biodegradable Fibers

This work aims to present the results of evaluating the coloristic properties of polylactic acid (PLA) fibers. PLA is common nowadays in much research, as it is a biodegradable plastic from renewable sources. However, little research is devoted to PLA fibers, and even less to applied research of colored fibers. The prepared color masterbatches, created using inorganic pigments, such as titanium dioxide and carbon black, were subsequently used to prepare dyed PLA fibers in mass. The fibers were drawn to the maximum drawn ratio. The properties of the pure and dyed fibers were investigated before and after accelerated light aging using Q-SUN equipment. The changes were recorded by Fourier Transform Infrared (FTIR) spectroscopy and colorimetric properties were recorded using a device spectrometer from TECHKON SpectroDens. We also evaluated thermal properties from the first heating via differential scanning calorimetry (DSC). The measurements were taken before and after the aging of the PLA fibers, in order to see the effect of aging on the supermolecular structure, excluding the influence of the preparation process and the influence of the kind of PLA. Using inorganic pigments showed sufficient color stability even after accelerated light aging, which is beneficial for using colored fibers in practice.

Utilization of modified epoxidized natural rubber and zinc oxide on properties of polylactic acid/epoxidized natural rubber blends: Mechanical properties, antibacterial efficiency and biodegradability

Polylactic acid (PLA) is a biopolymer with brittleness and no antibacterial efficiency, which can be solved by the combination with epoxidized natural rubber (ENR) due to polar-polar interaction and with modified zinc oxide nanoparticles (ZnO) regarding the releasing of zinc ions (Zn2+) and reactive oxygen species (ROS). To minimize self-interaction in each PLA and ENR molecular chain, ENR with different % epoxidation was modified (mENR) by grafting with sebacic acid (SA). The addition of mENR with 50 % mol to PLA significantly improved the properties of pure PLA in terms of mechanical and impact properties, toughness, and also provided disinfectant ability. Regarding antibacterial properties, the efficiency against Staphylococcus aureus and Escherichia coli was significantly improved by adding ZnO to the blends. Combination of mENR to PLA matrix during mixing operation increases improved ZnO dispersion and distribution in PLA/mENR blends. Thus, antibacterial efficiency had been enhanced using proper mENR:ZnO concentration ratios in the PLA matrix, relative to other modified ZnO types. Also, incorporation of mENR:ZnO enhanced impact strength and retarded biodegradability of the blends due to hydrophobicity of ENR in PLA matrix. The findings of the blends' properties suggest potential for new functional applications, especially in disinfectant sheet lamination products where strength and protection against bacterial growth together with proper degradation period are required.

Effects of annealing on the mechanical, thermal, and physical properties of 3D-printed PLA aged in salt water

Despite recent advances in understanding the performance of 3D-printed polylactic acid (PLA) parts, there is a gap to be covered before they can be safely used in marine applications. Given this need, this study evaluates the influence of annealing on the mechanical, thermal and physical properties of PLA specimens aged in salt water at 45 °C for 45 days. Results showed that adequate annealing (100 °C, 70 min) reduces the effects of aging on the flexural and dynamic mechanical properties. This is because the increased crystallinity and reduced void content in annealed specimens, also decreased their water adsorption and surface defects.

Effects of Nozzle Temperature on Mechanical Properties of Polylactic Acid Specimens Fabricated by Fused Deposition Modeling.

This paper investigates the effect of nozzle temperature, from 180 to 260 °C, on properties of polylactic acid (PLA) samples manufactured by fused deposition modeling (FDM) technology. The main objective of this research is to determinate an optimum nozzle temperature relative to tensile, flexural and compressive properties of printed specimens. After manufacturing, the samples exhibit an amorphous structure, without crystallization effects, independently of the fabrication temperature. In order to determine the influence of printing temperature on mechanical properties, uniaxial tensile, three-point flexural and compression strength tests were carried out. The obtained results suggest that a relative low printing temperature could reduce the material flow and decrease the density of the final prototype, with a negative effect on both the quality and the mechanical properties of the pieces. If temperature increases up to 260 °C, an excess of material can be deposited, but with no significant negative effect on mechanical parameters. There is an optimum nozzle temperature interval, depending on the considered piece and test, for which mechanical values can be optimized. Taking into account all tests, a recommended extruder temperature interval may be identified as 220-240 °C. This range encompasses all mechanical parameters, avoiding the highest temperature where an excess of material was observed. For this printing temperature interval, no significant mechanical variations were appreciated, which corresponds to a stable behavior of the manufactured specimens.

The Effects of Nucleating Agents and Processing on the Crystallization and Mechanical Properties of Polylactic Acid: A Review.

Polylactic acid (PLA) is a biobased, biodegradable, non-toxic polymer widely considered for replacing traditional petroleum-based polymer materials. Being a semi-crystalline material, PLA has great potential in many fields, such as medical implants, drug delivery systems, etc. However, the slow crystallization rate of PLA limited the application and efficient fabrication of highly crystallized PLA products. This review paper investigated and summarized the influence of formulation, compounding, and processing on PLA's crystallization behaviors and mechanical performances. The paper reviewed the literature from different studies regarding the impact of these factors on critical crystallization parameters, such as the degree of crystallinity, crystallization rate, crystalline morphology, and mechanical properties, such as tensile strength, modulus, elongation, and impact resistance. Understanding the impact of the factors on crystallization and mechanical properties is critical for PLA processing technology innovations to meet the requirements of various applications of PLA.

Enhanced Crystallization of Sustainable Polylactic Acid Composites Incorporating Recycled Industrial Cement.

Globally, the demand for single-use plastics has increased due to the rising demand for food delivery and household goods. This has led to environmental challenges caused by indiscriminate dumping and disposal. To address this issue, non-degradable plastics are being replaced with biodegradable alternatives. Polylactic acid (PLA) is a type of biodegradable plastic that has excellent mechanical properties. However, its applications are limited due to its low crystallinity and brittleness. Studies have been conducted to combat these limitations using carbon or inorganic nucleating agents. In this study, waste cement and PLA were mixed to investigate the effect of the hybrid inorganic nucleating agent on the crystallinity and mechanical properties of PLA. Waste cement accelerated the lamellar growth of PLA and improved its crystallinity. The results indicate that the flexural and impact strengths increased by approximately 3.63% and 76.18%, respectively.

Effect of infill pattern on the mechanical properties of PLA and ABS specimens prepared by FDM 3D printing

Fused deposition modelling (FDM) is a three-dimensional printing technique which has become more popular and spreading in many fields. In this process, the molten thermoplastic is deposited layer by layer using a heated nozzle. Users can set the infill pattern to save the material and printing time. The main objective of this study is to investigate the tensile properties of polylactic acid (PLA) and Acrylonitrile butadiene styrene (ABS) tensile specimens with different infill patterns such as lines, tri-hexagonal and lightning. Further, the test specimens were prepared as per ASTM D638 using Ender 3D printer with varying infill patterns. The specimens were subjected to tensile tests in a mechanical tensile testing machine. It was observed that the specimens with linear infill patterns obtained higher tensile strength than the tri-hexagonal and lightning pattern infilled specimens. Later on, a microstructural study was examined on the fractured surface using scanning-electron-microscopy (SEM). It shows that the line pattern specimens have more uniform structure when compared to hexagonal and lightning pattern specimens.

Enhancement of PLA-based Biopolymer Composite Physical Properties with Addition of Sucrose

Abstract Polylactic acid (PLA) is a biodegradable polymer that has poor barrier properties. Blending PLA with thermoplastic starch (TPS) is an alternative to improve the barrier properties of PLA. The purpose of this study is to improve the barrier properties and mechanical of PLA-based biopolymer composite by blending it with TPS and 5%wt of sucrose. Tensile strength, water vapour transmission rate, morphology, and degradability of biopolymer composite were examined. The morphology of PLA-TPSS bioplastic showing no pores and more homogenous which lead to best WVTR and mechanical result; however, the tensile strength by PLA-TPSS is reduced than pure PLA.

Enhancing biodegradable polymer surface wettability properties through atmospheric plasma treatmsurfaent and nanocellulose incorporation

This study investigates the effects of atmospheric plasma treatment on the surface properties of polylactic acid (PLA)/nanocrystalline cellulose (CNC) composites, aiming to improve their wettability and mechanical properties. The research utilizes a twin-screw extrusion process for fabricating PLA/CNC biocomposites, followed by surface modification using a custom-built, with a tenfold high-voltage atmospheric plasma system. The motivation of this treatment was to improved surface wettability and potential for enhanced adhesive bonding in ecological applications. These findings contribute to developing more sustainable composite materials by providing a method to improve the functionality of biodegradable polymers without compromising their environmental benefits.

Influence of the cell size and wall thickness on the compressive behaviour of fused filament fabricated PLA gyroid structures

The development of Additive Manufacturing (AM) has greatly facilitated the fabrication of cellular and lattice materials. Gyroid-based lattice structures, known for their distinctive properties such as interconnected porosity, high surface-to-volume ratio, and remarkable structural stiffness combined with specific energy absorption, have been extensively explored. Many studies examining the impact of design parameters on the mechanical properties of Gyroid lattice materials have utilized metal AM techniques. This research aims to evaluate the influence of two design parameters on the compressive properties of Gyroid structures obtained by fused filament fabrication (FFF). A full factorial analysis was employed to assess the effects of cell size and wall thickness on the compressive properties of polylactic acid (PLA) Gyroid lattices. Cell sizes were varied between 4 mm, 5 mm, and 10 mm, while wall thickness ranged from 0.4 mm, 0.6 mm, to 0.8 mm. After 3D printing, the print quality was assessed, samples were weighted and then subjected to compression testing. During compression, the lattices with 10 mm cells exhibited successive layer collapse, whereas the lattice with 4 mm and 5 mm cells displayed plastic deformation, marked by a plateau in the stress-strain curve. These behaviours were mostly independent of wall thickness, except for the 5 mm cell lattice with 0.4 mm wall thickness. The elastic modulus, yield stress and absorbed energy per volume aligned with the apparent density of the lattices, ranging between 1% and 12% of the bulk 3D printed material for both the stiffness and yield stress, and between 1% and 22% for the energy absorbed. Analysis of the fitted means indicated that doubling the cell size had a more significant impact on the measured properties than doubling the wall thickness, while doubling both the cell size and wall thickness exerted a more pronounced influence on the yield stress and strain. Notably, under the conditions of this study, the 3D printed PLA Gyroids behaved similarly to closed cell foams, despite their interconnected channels. Their compressive mechanical properties comparable to those of rigid polyurethane foams with closed cells.

Sustainable improvement in the polylactic acid properties of 3D printing filaments: The role of bamboo fiber and epoxidized soybean oil‐branched cardanol ether compatibilizer

AbstractPolylactic acid (PLA) is the prevailing raw material for fused deposition modeling (FDM) 3D printing filaments, offering benefits such as a low printing temperature, minimal shrinkage, and biodegradability. However, this material has challenges such as poor toughness, low heat deflection temperature, susceptibility to moisture‐induced thermal degradation, and high costs. This study addressed these concerns by incorporating natural bamboo fiber (BF) into PLA, elevating heat the deflection temperature and lowering the material costs. Additionally, a synthesized branched structure compatibilizer, in the form of epoxidized soybean oil‐branched cardanol ether (ESOn‐ECD), enhanced the toughness of PLA, the bonding strength between PLA and the BF surface, and the flowability of high‐fiber composites during processing and printing. The mechanical, thermal, and rheological properties were assessed, demonstrating the promising processing performance of PLA/BF/ESO3‐ECD. The fully biobased composite exhibits strength, toughness, good processability, excellent 3D printability, and durability, implying substantial potential in FDM 3D filament production.Highlights Bio‐based PLA/bamboo fiber/ESO3‐ECD FDM 3D printing filaments were developed. The excellent nucleation ability of the bamboo fibers enhances the crystallization rate and crystallinity of PLA. The epoxy values and branching degree of ESOn‐ECD are crucial for its effective modification.

Enhancing mechanical properties of polylactic acid through the incorporation of cellulose nanocrystals for engineering plastic applications

This study investigates the potential of enhancing the mechanical properties of polylactic acid (PLA) using cellulose nanocrystals (CNC). Recognized for their high specific strength and stiffness, CNCs are considered to improve the performance of PLA in engineering plastic applications. The synthesis involves a twin-screw extrusion process, which facilitates the uniform dispersion of CNC within the PLA matrix. The mechanical properties, including tensile strength and elongation at break, are comprehensively analyzed, highlighting the effects of CNC concentrations on the performance of PLA composites. Notably, the addition of 1 wt% CNC resulted in a 20% increase in strain at break compared to pure PLA, demonstrating enhanced ductility. Additionally, the thermal resistance of the composite increased by 0.3% with the inclusion of 5 wt% CNC. This study highlights the positive effect of CNC addition on the mechanical properties of PLA composites, making them more suitable for specialized engineering uses.

Optimizing FDM process parameters: predictive insights through taguchi, regression, and neural networks

Fused deposition modelling (FDM) is a popular additive manufacturing process used for rapid prototyping and the production of complex geometries. Despite its popularity, FDM’s susceptibility to variations in numerous process parameters can significantly impact the quality, design, functionality, and mechanical properties of 3D printed parts. This study explores thirteen FDM process parameters and their influence on the mechanical properties of polylactic acid (PLA) polymer, encompassing surface roughness, warpage, tensile and bending strength, elongation at break, deformation, and microhardness. The optimum parameters were identified alongside key contributors by applying the Taguchi method, signal-to-noise ratios, and analysis of variances (ANOVA). Notably, specific FDM parameters significantly affect the surface profile, with layer thickness contributing 32.65% and fan speed contributing 8.59% to the observed variations. Similarly, warping values show notable influence from nozzle temperature (29.53%), wall thickness (16.74%), layer thickness (16.56%), and retraction distance (12.80%). Tensile strength is primarily determined by wall thickness (31.83%), followed by infill percentage (26.73%) and infill pattern (16.18%). Elongation at break predominantly correlates with wall thickness (44.82%), with a supplementary contribution from nozzle temperature (10.90%). Microhardness lacks a dominant parameter. Bending strength variations primarily arise from layer thickness (38%), wall thickness (37.6%), and infill percentage (9.17%). Deformation tendencies are influenced by layer thickness (19.20%), print speed (11.37%), wall thickness, and fan speed (10.9% each). The optimized dataset of FDM process parameters was then employed in two prediction models: multiple-regression and artificial neural network (ANN). Evaluation based on the correlation coefficient (R2) and root mean squared error (RMSE) indicates that the ANN model outperforms the multiple-regression approach. The results indicate that precise control of FDM parameters, coupled with ANN predictions, facilitates the fabrication of 3D printed parts with the desired mechanical characteristics.

Microstructural and Hydrophilic Properties of Polylactide Polymer Samples with Various 3D Printing Patterns.

The aim of the work is to study the effect of the 3D printing process on the microstructural and hydrophilic properties of polylactic acid (PLA) samples with various model printing patterns obtained from the black filament PLA by sequentially applying polymer layers using the FDM (fused deposition modeling) method. X-ray phase analysis revealed the partial crystallization of PLA polymer chains in the printed samples, which occurs under thermal and mechanical action on the original amorphous PLA filament during 3D printing to varying degrees, depending on the geometry of the pattern and the morphology of its surface. At the same time, IR spectroscopy data indicate the preservation of all intrastructural chemical bonds of polylactide. Measured at the original installation, the values of the wetting edge angles on the surface of the printed samples are in the range φ = 50-60°, which is significantly less than the right angle. This indicates the hydrophilic properties of the whole sample's surface. At the same time, the influence of different geometries of model drawings in printed samples was found not only on the morphology of the sample's surface according to SEM data but also on its wettability.

Study on the Properties of PLA- and PP-Based Films for Food Applications Incorporating Orange Peel Extract from Agricultural by-Products.

The aim of this work was to develop active packaging based on polypropylene (PP) and polylactic acid (PLA) matrices using a high value by-product extracted from orange peel as an active compound for food packaging applications. Different films with and without orange peel extract (OPE) based on PP and PLA were obtained via cast extrusion and characterized in terms of their mechanical, thermal, optical, and sealing properties. The films obtained were transparent, but when OPE was incorporated, the transmittance spectrum decreased, causing slight coloration. Mechanical properties were affected by the incorporation of OPE, as elongation at break and tensile strength increased in the cross-direction of the PP film, although the main differences found were related to the polymer itself. In addition, sealing strength also increased via the incorporation of OPE in the PP matrix. However, thermal properties were not affected by OPE in the PP matrix but slightly decreased stability in PLA. Regarding antimicrobial activity in in vitro studies, no inhibition of the growth of Listeria innocua, Saccharomyces cerevisiae, Aspergillus niger, or Escherichia coli was observed. Finally, antioxidant activity was observed in in vitro studies with 2,2-Diphenyl-1picrylhydrazyl (DPPH) radical. The results of this study showed that the obtention of materials with OPE incorporated into the PLA and PP matrix is feasible. The new materials obtained can be used for applications of oxidation-sensitive fresh products.

Surface Thermodynamic Properties of Poly Lactic Acid by Inverse Gas Chromatography.

Poly lactic acid (PLA) is one of the most commonly used bio-derived thermoplastic polymers in 3D and 4D printing applications. The determination of PLA surface properties is of capital importance in 3D/4D printing technology. The surface thermodynamic properties of PLA polymers were determined using the inverse gas chromatography (IGC) technique at infinite dilution. The determination of the retention volume of polar and non-polar molecules adsorbed on the PLA particles filling the column allowed us to obtain the dispersive, polar, and Lewis's acid-base surface properties at different temperatures from 40 °C to 100 °C. The applied surface method was based on our recent model that used the London dispersion equation, the new chromatographic parameter function of the deformation polarizability, and the harmonic mean of the ionization energies of the PLA polymer and organic molecules. The application of this new method led to the determination of the dispersive and polar free surface energy of the adsorption of molecules on the polymeric material, as well as the glass transition and the Lewis acid-base constants. Four interval temperatures were distinguished, showing four zones of variations in the surface properties of PLA as a function of the temperature before and after the glass transition. The acid-base parameters of PLA strongly depend on the temperature. The accurate determination of the dispersive and polar surface physicochemical properties of PLA led to the work of adhesion of the polar organic solvents adsorbed on PLA. These results can be very useful for achieving reliable and functional 3D and 4D printed components.