Poly Lactic Acid Research Articles

Sustainable 3D printed poly (lactic acid) (PLA)/Hazelnut shell powder bio composites for design applications

In the context of seeking sustainable solutions for developing innovative materials and products by an efficient use of natural resources and recycling waste, with an increasing focus on circular economy and mitigating environmental impact, the presents research aims to use biomass and agricultural residues as raw materials for bio composite production. Specifically, valorizing European hazelnut waste presents a unique opportunity to devise innovative formulations for 3D printing, leveraging both the mechanical properties and aesthetic appeal of lignocellulosic bio composites. In detail, this work aimed at the investigation of new poly(lactic acid) (PLA)/Hazelnut Shell Powder formulations for 3D printing design applications exploiting the woody aesthetic effect of these bio composites. A pellet 3D printer was used to bypass the filament production. Three different Hazelnut Shell Powder content (from 10 up to 30 wt%) were investigated and a design of experiment was carried out to generate response surfaces able to identify the best printing conditions to optimize flexural, tensile and impact properties. Finally, the effect of three different raster angles (0°, ±45° and 90°) on the mechanical properties was investigated. The best configuration was: 220 °C of nozzle temperature, 25 mm/s of printing speed and ±45° of raster angle. With this configuration, prototypes of ornamental pots, jewellery and home furniture were produced as demonstrators.

Blown film of PLA for packaging with green tea and fish industrial residues: an insight on their properties

The use of food waste on the production of packaging can be seen as a promising strategy to cost reduction and new properties. Moreover, packaging, besides food physical protection, should establish a barrier to light and oxygen together with antioxidant and antibacterial activity, to extend the shelf-life of perishable products. In this study, PLA films with the incorporation of natural additives (cold fish protein - cFG and green tea extract - GTE) were successfully produced by blown film extrusion. While PLA exhibits favorable water vapor barrier properties due to its hydrophobic nature, a significant drawback in terms of high oxygen permeability. Although the cFG and GTE incorporation into the PLA matrix decreased the water vapor barrier and mechanical properties, it improves the oxygen barrier along with wettability and antioxidant activity. Moreover, GTE polyphenol compounds seem to improve molecular interaction between the PLA and cFG particles by establishing a better dispersion with enhanced compatibility. These results exhibit the benefits of adding cFG and GTE to a PLA matrix to produce an active film with reliable properties for food packaging.

A novel poly (lactic-acid) and poly (butylene adipate-co-terephthalate) blend membrane modified with hesperidin for oily water emulsions separation

The oily wastewater produced by a variety of industrial operations presents a serious threat to both humans and the environment. Separation efficiency, good mechanical stability, high flux, and recyclability are critical parameters for a suitable oil-water separation membrane. In this study, a novel blend membrane of (poly (lactic acid)/poly (butylene adipate-co-terephthalate)) with hesperidin-NPs was synthesized by using the phase inversion technique to effectively separate oily-water emulsions. Herein, hesperidin (HSP) was harnessed for the first time as a green agent to optimize its content in the polymeric matrix. (FTIR) Fourier transform infrared spectroscopy, (FESEM) Field emission scanning electron microscopy, (CA) contact angle, mechanical tester, pore size and porosity were utilized to comprehensively characterize the manufactured (PLA/PBAT/HSP) membranes. The current work presents the proposed interaction mechanism between the contents of PLA/PBAT/HSP and the interaction mechanism of PLA/PBAT/HSP membrane with H2O molecules. The synthesized (PLA/PBAT/HSP) membrane manifested high wettability and has a 49° water contact angle and oleophobicity under a water contact angle of 146±2° for diesel oil. The PLA/PBAT membrane exhibited a homogeneous and symmetric spongy-like structure from top to bottom across its entire cross-section with very tiny active layer observed at the top surface of the membrane in FESEM images. Meanwhile, incorporating of 0.0125wt.% HSP into the casting solution has resulted in a significant change in the structural morphology. Furthermore, upon adding the HSP to the polymeric matrix, distinct changes in the structure were formed, which resulted in enhancing the mechanical features (tensile strength) of the membranes. Modified membrane with 0.025wt.% HSP displayed an optimal flux for pure water (220.5L/m2.h1) and the modified membranes maintained a high rejection (more than 99%) against oil-water emulsions. Outcomes demonstrated that the improved permeation and separation characteristics of the (PLA/PBAT/HSP) membranes could present a potential option to treat applications that use oily wastewater.

Biodegradable microplastics pose greater risks than conventional microplastics to soil properties, microbial community and plant growth, especially under flooded conditions

Biodegradable plastics (bio-plastics) are often viewed as viable option for mitigating plastic pollution. Nevertheless, the information regarding the potential risks of microplastics (MPs) released from bio-plastics in soil, particularly in flooded soils, is lacking. Here, our objective was to investigate the effect of polylactic acid MPs (PLA-MPs) and polyethylene MPs (PE-MPs) on soil properties, microbial community and plant growth under both non-flooded and flooded conditions. Our results demonstrated that PLA-MPs dramatically increased soil labile carbon (C) content and altered its composition and chemodiversity. The enrichment of labile C stimulated microbial N immobilization, resulting in a depletion of soil mineral nitrogen (N). This specialized environment created by PLA-MPs further filtered out specific microbial species, resulting in a low diversity and simplified microbial community. PLA-MPs caused an increase in denitrifiers (Noviherbaspirillum and Clostridium sensu stricto) and a decrease in nitrifiers (Nitrospira, MND1, and Ellin6067), potentially exacerbating the mineral N deficiency. The mineral N deficit caused by PLA-MPs inhibited wheatgrass growth. Conversely, PE-MPs had less effect on soil ecosystems, including soil properties, microbial community and wheatgrass growth. Overall, our study emphasizes that PLA-MPs cause more adverse effect on the ecosystem than PE-MPs in the short term, and that flooded conditions exacerbate and prolong these adverse effects. These results offer valuable insights for evaluating the potential threats of bio-MPs in both uplands and wetlands.

Effects of heat treatment on the mechanical properties of 3D-printed polylactic acid: Study of competition between crystallization and interlayer bonding

Fused deposition modeling (FDM) is a popular additive manufacturing technique because of its flexibility, customization, cost-effectiveness, and eco-friendliness. However, due to the layer-by-layer fabrication process and the formation of voids, the mechanical properties of printed parts are lower than other manufacturing techniques. As a solution, heat treatments can effectively mitigate additive manufacturing limitations and improve the mechanical properties of printed parts. The interlayer bonding and subsequently mechanical properties of 3D-printed PLA were affected by the competition between crystallization and chain diffusion of 3D-printed polylactic acid during the heat treatment process. This competition highlights the importance of optimization of heat treatment. Additionally, crystallite growth could cause a reduction in some mechanical properties, like elongation. The size, distribution, and content of voids are also influenced by heat treatment, playing a crucial role in the mechanical properties of 3D-printed parts. In this research, printed samples were heat-treated at temperatures of 75 ºC, 110 ºC, and 130 ºC for two hours. Furthermore, compression-molded samples were fabricated to inspect a comparison of mechanical properties between the traditional and additive manufacturing methods and investigate the effect of layer-by-layer fabrication on these properties. Sample AM-75 showed a 15.5% improvement in bonding strength compared to the non-annealed printed sample, resulting in an increase of 20.2% in tensile strength and 275% in impact strength. Moreover, annealing the sample at 130 ºC resulted in a 7.6% reduction in porosity and a significant improvement of 220% in crystallinity, heat deflection temperature, flexural modulus, and flexural strength, with improvements of 121%, 29.5%, and 15.2% respectively.

Bioinspired poly-dopamine/nano-hydroxyapatite: an upgrading biocompatible coat for 3D-printed polylactic acid scaffold for bone regeneration.

Poly-lactic acid (PLA) has been proposed in dentistry for several regenerative procedures owing to its biocompatibility and biodegradability. However, the presence of methyl groups renders PLA hydrophobic, making the surface less ideal for cell attachment, and it does not promote tissue regeneration. Upgrading PLA with inductive biomaterial is a crucial step to increase the bioactivity of the PLA and allow cellular adhesion. Our purpose is to evaluate biocompatibility, bioactivity, cellular adhesion, and mechanical properties of 3D-printed PLA scaffold coated with poly-dopamine (PDA) and nano-hydroxyapatite (n-HA) versus PLA and PLA/n-HA scaffolds. The fused deposition modelling technique was used to print PLA, PLA with embedded n-HA particles, and PLA scaffold coated with PDA/n-HA by immersion. After matrices characterization for their chemical composition and surface properties, testing the compressive strength was pursued using a universal testing machine. The bioactivity of scaffolds was evaluated by monitoring the formation of calcium phosphate compounds after simulated body fluid immersion. The PLA/PDA/n-HA scaffold showed the highest compressive strength which was 29.11 ± 7.58 MPa with enhancing calcium phosphate crystals deposition with a specific calcium polyphosphate phase formed exclusively on PLA/PDA/n-HA. With cell viability assay, the PDA/n-HA-coated matrix was biocompatible with increase in the IC50, reaching ⁓176.8 at 72 without cytotoxic effect on the mesenchymal stem cells, promoting their adhesion and proliferation evaluated by confocal microscopy. The study explored the biocompatibility, bioactivity, and the cell adhesion ability of PDA/n-HA coat on a 3D-printed PLA scaffold that qualifies its use as a promising regenerative material.

Coupled engineering strategy of CYB2 deletion and ACS1 overexpression improves cellulosic lactic acid production by Saccharomyces cerevisiae

Lactic acid plays a significant role in the food industry as a natural preservative and serves as a platform chemical for the production of biodegradable poly-lactic acid. While its sustainable production through fermentation using cellulosic biomass instead of traditional sugar and starch raw materials shows promise, there remains limited information available on this method. In this study, a xylose-fermenting and lactic acid-tolerant Saccharomyces cerevisiae strain (BK01) was engineered for improved cellulosic lactic acid production using the promising energy crop, kenaf. Specifically, CYB2 was deleted to inhibit lactic acid consumption (BK02), which was further engineered by ACS1 overexpression to remove the cytotoxic acetate derived from cellulosic biomass (BK03). The BK03 produced 3.25-fold more lactic acid from kenaf pulp hydrolysate than the parental strain (BK01). During pH-controlled fermentation, lactic acid production by BK03 reached a titer of 31 g/L and a productivity of 1.30 g/L-h, the highest value reported so far. This is one of the few studies on yeast-based lactic acid production from lignocellulose.

The impacts of biodegradable and non-biodegradable microplastic on the performance and microbial community characterization of aerobic granular sludge

IntroductionMicroplastics (MPs), identified as emerging contaminants, have been detected across diverse environmental media. Their enduring presence and small size facilitate the adsorption of organic pollutants and heavy metals, leading to combined pollution effects. MPs also accumulate in the food chain thus pose risks to animals, plants, and human health, garnering significant scholarly attention in recent years. Aerobic granular sludge (AGS) technology emerges as an innovative approach to wastewater treatment. However, the impacts of MPs on the operational efficiency and microbial characteristics of AGS systems has been insufficiently explored.MethodsThis study investigated the effects of varying concentration (10, 50, and 100 mg/L) of biodegradable MPs (Polylactic Acid, PLA) and non-biodegradable MPs (Polyethylene Terephthalate, PET) on the properties of AGS and explored the underlying mechanisms.Results and discussionsIt was discovered that low and medium concentration of MPs (10 and 50 mg/L) showed no significant effects on COD removal by AGS, but high concentration (100 mg/L) of MPs markedly diminished the ability to remove COD of AGS, by blocking most of the nutrient transport channels of AGS. However, both PLA and PE promoted the nitrogen and phosphorus removal ability of AGS, and significantly increased the removal efficiency of total inorganic nitrogen (TIN) and total phosphorus (TP) at stages II and III (P < 0.05). High concentration of MPs inhibited the growth of sludge. PET noticeably deteriorate the sedimentation performance of AGS, while 50 mg/L PLA proved to be beneficial to sludge sedimentation at stage II. The addition of MPs promoted the abundance of Candidatus_Competibacter and Acinetobacter in AGS, thereby promoting the phosphorus removal capacity of AGS. Both 50 mg/L PET and 100 mg/L PLA caused large amount of white Thiothrix filamentous bacteria forming on the surface of AGS, leading to deterioration of the sludge settling performance and affecting the normal operation of the reactor. Comparing with PET, AGS proved to be more resistant to PLA, so more attention should be paid to the effect of non-biodegradable MPs on AGS in the future.

Experimental investigation of the polymer-metal hybrids interfacial bonding fabricated by fused deposition modeling

In this paper, the fabrication of polymer-metal hybrids by fused deposition modeling was evaluated. 6061 aluminum alloy and polylactic acid were used in the manufacturing process. Also, to strengthen the bonding between the metal and polymer components, a two-component epoxy adhesive was used. The pull-off adhesion test was performed to evaluate the interfacial bonding strength of the specimens. In this study, the effect of bed temperature, print speed, printer nozzle diameter, and aluminum sheet surface roughness on the bond strength of polymer-metal hybrids has been investigated. The results showed that increasing the bed temperature, and aluminum sheet surface roughness, and also decreasing the print speed led to increase the bond strength of polymer-metal hybrids. Finally, by using the experimental data, an optimal specimen was produced. The interfacial bonding strength of the optimal specimen is about 64% stronger than the initial specimen.

Exploring the Potential of Sustainable Biopolymers as a Shield against Electromagnetic Radiations.

The increasing demand for biodegradable and environmentally friendly materials is shifting the focus from traditional polymer composites to biocomposites in various applications, especially in electromagnetic shielding. Effective utilization of biopolymers demands improved properties and can be achieved to a certain extent by functionalization. Biopolymers such as cellulose, polylactic acid, and starch are some of the potential candidates for mitigating electromagnetic pollution in next-generation electronic devices because of their high aspect ratio, flexibility, light weight, high mechanical strength, thermal stability, and tunable microwave absorption to the electromagnetic interference (EMI) shielding composites. This Review provides an overview of the current advancements in EMI shielding materials and outlines recent research on EMI shielding composites that utilize various biodegradable polymer structures.

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.

Novel catalyst-solvent system for high molecular weight polylactic acid synthesis via azeotropic solution polycondensation method

ABSTRACT Polycondensation for PLA synthesis is widely used due to its cost-effectiveness, but it often leads to low molecular weight PLA. To address this limitation, researchers have explored different catalysts, with the stannous chloride and p-toluene sulfonic acid combination being a popular choice. However, this method typically yields PLA with a MW of no more than 35000 g/mol, which is unsuitable for commercial applications. In contrast, ring-opening polymerization is considered the most effective method for synthesizing high MW PLA, despite its complexity and cost. Industrial-scale production predominantly employs ROP due to its capability to produce high MW PLA. The use of stannous octoate as a catalyst for ROP has shown promise in synthesizing higher MW PLA. However, its sensitivity to water limits its use in polycondensation, where stannous chloride is commonly employed but is not capable of synthesizing high MW PLA. This study explores the use of stannous octoate for the synthesis of high MW PLA with higher yield.

Ultrasonic welding of Cork Wood/PLA composites: effect of welding factors on lap shear strength performance

Ultrasonic welding of Cork Wood/PLA composites: effect of welding factors on lap shear strength performance

Preparation of tomato peel pomace powder/polylactic acid foams under supercritical CO2 conditions: Improvements in cell structure and foaming behavior.

Polylactic acid (PLA) is an eco-friendly material that can help address the problems of petroleum depletion and pollution. Blending renewable biomass materials with PLA to create composite foams with a tunable pore structure, superior performance, and low cost is a green technique for improving the pore structure and mechanical characteristics of single PLA foams. PLA/TP composites were created using melted tomato peel pomace powder (TP), which has a lamellar structure, as a reinforcing agent. Then, the relationship between the vesicle structure, morphology, and properties of the PLA/TP composite foams produced through supercritical CO2 intermittent foaming were investigated. The findings revealed that TP considerably enhanced the rheological characteristics and crystalline behavior of PLA. The PLA/TP composite foam had a better cell structure, compression characteristics, and wettability than pure PLA. The expansion ratio of the PLA/TP composite could reach 18.8, and its thermal conductivity decreased from 174.2 mW/m·K at 100 °C to 57.8 mW/m·K at 120 °C. Furthermore, annealing before foaming decreased the average composite foam blister size from 110.09 to 66.53 μm, and the annealing process also improved compression performance. This study contributes to solving environmental difficulties and creating PLA foams with controlled bubble structures, uniform bubble sizes, and outstanding overall performance.

Development and characterization of groundnut shell‐derived biocarbon‐reinforced polylactic acid composite filaments for FDM

AbstractBiochar, a carbon‐rich biomass material has emerged as promising reinforcement and offers versatile applications and potential benefits in various fields, especially in fused deposition modeling (FDM). This study focuses on the development and characterization of groundnut shell‐derived biocarbon (GNSC) reinforced polylactic acid (PLA) filaments for FDM. The GNSC was synthesized through pyrolysis using a tubular furnace at temperatures 700, 800, and 900°C. Synthesized carbon was characterized using Raman spectroscopy, XRD, and SEM analysis. The results showed that the synthesized carbon particles were graphitic, spherical, and nanosized with an average diameter of 40 nm. The preferred biocarbon material, GNSC800 was selected for its high carbon content (98.25%) observed through EDX analysis. Composite filaments were produced with different GNSC800 loadings of 0.25%, 0.5%, and 0.75% using solvent casting and extrusion techniques. Thermal stability was evaluated using TGA and DSC, which showed improved properties with the addition of biocarbon. The mechanical properties and electrical conductivity were enhanced with the inclusion of biocarbon. The data were also validated using ANOVA and Tukey's test. Filament with the 0.5 wt% loading showed the most favorable thermomechanical properties exhibiting a 39.8% increase in tensile strength and a 17.5% improvement in tensile modulus.

Optimization of energy absorption and vibration behaviour of TPMS Schwarz P and Schoen Gyroid lattice structures using Taguchi L9 orthogonal array

In this study, the optimization of printing parameters in fused deposition modeling (FDM) is addressed, focusing on their impact on energy absorption and vibration behaviour of triply periodic minimal surface (TPMS) lattice structures, specifically Pseudo-periodic-based Schwarz P and Schoen Gyroid designs. The experimental design employs a Taguchi L9 orthogonal array involving layer height (0.15 mm, 0.30 mm, 0.45 mm), build orientation (0°, 45°, 90°), and extruder temperature (190°C, 200°C, 210°C) as inputs. These lattice structures are generated through Math Mod and simulated using Blender, with Autodesk Mesh mixer refining the STL file. The lattice fabrication employs PLA (polylactic acid). Comparative analysis is conducted against a high-density solid structure lacking lattice design. Optimal parameters for Schwarz P lattice are found to be 0.45 mm layer height, 0° build orientation, and 200°C extruder temperature, while for Schoen Gyroid lattice, 0.30 mm layer height, 0° build orientation, and 210°C extruder temperature. Solid structure optimization yields 0.30 mm layer height, 90° build orientation, and 190°C extruder temperature. Solid structures outperform Schwarz-P and Schoen-Gyroid in energy absorption and vibration behaviour, with Schwarz P showing superior properties over Schoen Gyroid.

Enhancing the toughness of poly(lactic acid) with a novel, highly flexible and biodegradable polyester: poly(ethylene adipate-co-terephthalate) terephthalate

Enhancing the toughness of poly(lactic acid) with a novel, highly flexible and biodegradable polyester: poly(ethylene adipate-co-terephthalate) terephthalate

Integration of BMP-2/PLGA microspheres with the 3D printed PLGA/CaSO4 scaffold enhances bone regeneration

Treatment of large and complex irregular bone defects is a major clinical challenge in orthopedic surgery. The current treatment includes bone transportation using the Ilizarov technique and bone cement repair using the Masquelet technique, but they require long-term manual intervention or secondary operation. To improve this situation, we compared the different implanting materials in the literature published in the past 10 years, finding that glycolic acid copolymer (PLGA) and Calcium sulfate (CaSO4) are appropriated to be used as synthetic bone materials due to their advantages of easy-availability, nontoxicity, osteogenic properties and rapid degradation. Meanwhile, the development of 3D printing technique and devices makes it relatively easier to synthetize customized bio-mimetic porous scaffolds, thus facilitating the release of modified protein. In this study, we compounded BMP-2/PLGA microspheres with polylactic glycolic acid copolymer/CaSO4 (PC) 3D printed scaffold to improve the osteogenic properties of the scaffold. The result of our in vitro experiment demonstrated that the prepared PCB scaffold not only had satisfactory bio-compatibility, but also promoted osteogenic differentiation. This 3D printed scaffold is capable to accelerate the repair of complex bone defects by promoting new bone formation, suggesting that it may prove to be a potential bone tissue engineering substitute.

Tribological performance of functional coated fiber reinforced additively manufactured polymer composite

Additive manufacturing has witnessed an upward trend in utilization across diverse industries in recent years. This study examines the tribological properties of polymer composites produced using additive manufacturing. The polymer composites were produced using the fusion deposition modeling process. Subsequently, they undergo thermal spray coating and spin coating processes that deposit hafnium carbide particles onto their surface. The wear test studies were conducted at three distinct temperature levels in accordance with the ASTM standard procedure. The findings demonstrated that the application of a ceramic particle coating led to a substantial decrease in the specific wear rates. Additionally, there were observed differences in the wear rates depending on the specific methods used for applying the coating. The application of thermal coating shown high efficacy in reducing wear rates and safeguarding the underlying materials against material loss. The uncoated carbon fiber reinforced polylactic acid (PLA-CF) material showed a slightly significant amount of material degradation as the test chamber temperature increased, in comparison to the coated specimens. The average specific wear rate of the thermally coated carbon fiber reinforced polylactic acid specimen at a temperature of 70 °C is 0.000156 kg Nm−1.

Segmental Mobility in Linear Polylactides of Various Molecular Weights

In this work we synthesized and studied a series of linear polylactides (PLA) with a fixed L/D -lactide stereoisomer ratio, covering together the wide range of molecular weights, Mn, from ∼6 to ∼80 kg/mol. The basic aims are the segmental mobility mapping, in terms of time scale and fragility, the recording of the Mn dependences of the glass transition temperature and fragility, and, finally, the comparison with corresponding findings from the literature. Obviously, the direct Mn effects on Tg are assessed by preserving PLA at the amorphous state, i.e., via melting and relatively fast cooling. The segmental mobility is studied by conventional and temperature modulated calorimetry, whereas the molecular dynamics is assessed employing the technique of broadband dielectric spectroscopy in combination with proper critical analysis and evaluation routes. The calorimetric and dielectric Tg(Mn) trends were found consistent between each other as well as with previous findings in similar systems, both with respect to experimental findings and theoretic predictions for PLAs of similar L/D ratio. The Mn threshold of entanglements seems to lay between 13 and 28 kg/mol. The fragility index of the α relaxation, i.e., the dielectric analogue of the glass transition, exhibits a similar dependence to that of Tg(Mn). When decreasing Mn to very low values, the high fragility (∼150) drops down to 0 (Mn∼6 kg/mol), denoting the vanishing of the polymer chains’ cooperativity. Qualitatively interesting alternations are recorded in the dielectric strength of the α relaxation and the relaxation times width. The effects are discussed in terms of the various parameters co-affecting the polymer dynamics, namely, chain lengths, free volume and dynamical heterogeneities.