Poly Lactic Acid Composites Research Articles

The impact of fire retardants on the mechanical and thermal characteristics of hemp fiber-reinforced polylactic acid composites

The impact of fire retardants on the mechanical and thermal characteristics of hemp fiber-reinforced polylactic acid composites

Preparation of environmentally friendly ionic liquids-toughened polylactic acid/nanofibrillated cellulose composites with high strength and precipitation resistance

Polylactic acid (PLA) is one of the most promising biodegradable materials, but poor toughness severely limits its application. Ionic liquids (ILs) have excellent plasticizing effects on PLA, but strength reduction and plasticizer precipitation remain worrisome. Herein, nanofibrillated cellulose (NFC), with excellent morphology, high modulus and strength, was prepared to reinforce PLA plasticization systems. Moreover, its numerous surface hydroxyl groups were tailored to bond with ILs, reducing plasticizer precipitation. The different sulfonation degrees of NFCs (low LSNFC, medium MSNFC, high HSNFC) and the influence of NFC amounts (0–7 wt%) on the mechanical, thermal and plasticizer precipitation properties of PLA composites were investigated. The results indicate that network-like C2/C3-sulfonated NFCs were successfully prepared through simple processing steps. Noteworthy, the tensile elongations of PLA composites increased with the addition of IL-XSNFC (all three degrees), with no significant reduction in tensile strength and modulus. The addition of 7 wt% IL-HSNFC resulted in an elongation of 25.01 % for PLA composites, which is 3.6 times that of pure PLA. Adding 3 wt% IL-MSNFC achieved ultra-high impact toughness of 3.19 kJ/m2, nearly double that of pure PLA. Interestingly, with increasing sulfonation degree, the amount of ILs precipitation in PLA composites significantly decreased. The precipitation rate of the PLA composite with IL-HSNFC is only 24 % of the counterparts with IL-NFC. This work presents an innovative method to improve interface compatibility, providing a new strategy to reduce plasticizer precipitation and broaden the application scope of PLA.

A new strategy to prepare bio-based polylactic acid modifier for multi-functionality: Dopamine-grafted modified lignin

Currently, to address the performance deficiencies associated with high brittleness, inadequate thermal stability, and susceptibility to hydrolysis in polylactic acid (PLA), it is common practice to incorporate multiple or high proportions of additives. However, this approach raises concerns regarding interface compatibility, energy consumption, and environmental impact. In this context, we introduce an environmentally friendly, bio-based PLA modifier that is facile to prepare and facilitates multi-functional applications at a minimal dosage. The presence of a benzene ring structure in lignin endows the material with ultraviolet (UV) resistance, thermal stability, and hydrophobic characteristics, while the exceptional adhesion properties of polydopamine (PDA) enhance interfacial compatibility. A novel biomass polylactic acid modifier, designated as OL@PDA, has been synthesized by modifying low-molecular-weight lignin (OL) with PDA. Comparative analysis of OL@PDA/PLA composite materials reveals a 14.08 % increase in tensile strength and a 42.00 % enhancement in elongation at break relative to pure PLA. The incorporation of the lignin-derived benzene ring structure effectively transforms PLA from a hydrophilic to a hydrophobic material. Furthermore, the UV transmittance at 400 nm (T400 nm%) is recorded at 65.8 % for pure PLA, which significantly decreases to below 5 % for OL@PDA/PLA composites. The integration of OL@PDA as a modifier in PLA materials yields comprehensively performance enhancements while maintaining a low additive concentration.

Full bio-based flame retardant towards multifunctional polylactic acid: Crystallization, flame retardant, antibacterial and enhanced mechanical properties

The preparation of flame-retardant high-performance polylactic acid (PLA) composites by adding green flame retardants have always been a challenge. In this work, an intumescent flame-retardant PCR based on phytic acid, chitosan, and resveratrol was successfully designed. Adding 4 wt% of PCR, the PLA-PCR composite was classified as UL-94 V-0 grade, with a LOI value increasing from 19.7 % (pure PLA) to 26.0 %, a peak heat release rate decreasing from 433 to 344 kW/m2. Owing to excellent compatibility of PCR, the mechanical strength and toughness of PLA-PCR composites have been improved, as reflected by a ~ 16 % increase in tensile strength, a ~ 73 % increase in impact strength and a ~ 57 % increase in toughness. In addition, PCR also presented plasticization effect on PLA, making it easier to process. This work provided a highly efficient and environmental-friendly modification approach for the development of multifunctional polymers.

Fabrication of composite RGD-tagged poly(lactic acid)-graphene oxide nanofiber containing bone-forming peptide-3 loaded-dendritic silica nanoparticles for bone regeneration in rabbit

In the current study, polylactic acid (PLA)/graphene oxide (GO) based composite scaffolds were fabricated by electrospinning method and then covalently modified with bone-forming peptide-3 (BFP-3)-loaded thiol-functionalized dendritic mesoporous silica nanoparticles (BFP-3@HS-DMSNs) and RGD. In this regard, PLA electrospinning nanofibers and composite of PLA/GO electrospinning nanofibers containing 0.02, 0.01, 0.04, 0.1, 0.2 % of GO were prepared and characterized in terms of mechanical strength, nanofibers diameter, thermal stability, crystallinity, specific surface area, total pore volume and cell adhesion properties. Among the prepared composites, PLA nanofibers containing 0.02 % GO demonstrated superior mechanical and morphological characteristics along with better cell adhesion for mesenchymal stem cell. Then, the PLA/0.02 %GO nanofiber was treated with plasma and consequently modified with N-(2-aminoethyl)maleimide linker which was applied for Cys-RGD and BFP-3@HS-DMSNs conjugation. The obtained results showed desirable adhesion of PLA/0.02 %GO nanofiber after incorporation of RGD (5 % of maleimide groups of the linker) and DMSNs which significantly increase cell adhesion potency (1.53 folds). By incorporation of BFP-3@HS-DMSNs (equivalent to 0.1 µg of BFP-3) to the RGD-tagged PLA/0.02 %GO nanofiber, the scaffold demonstrated better cytocompatibility and MSC differentiation to osteoblast based on biomineralization assay via alizarin red (4.2 folds) and alkaline phosphatase activity (1.7 folds) tests. In preclinical stage, after skull defect creation in rabbits, 5 treatments groups comprising PLA/0.02 %GO nanofiber, PLA/0.02 %GO/DMSNs, PLA/0.02 %GO/DMSNs/Cys-RGD, PLA/0.02 %GO/BFP-3@DMSNs and PLA/0.02%GO/BFP-3@DMSNs/Cys-RGD were used for bone regeneration in skull defects. After 3 months, the implantation of PLA/0.02GO/BFP-3@DMSNs/Cys-RGD showed higher bone regeneration based on CBCT imaging (18.875 mm2 bone formed area) in comparison with other treatment groups. This hybrid multimodal platform is purposely organized interactive processes which lead to potential bone regeneration.

3D‐printing continuous plant fiber/polylactic acid composites with lightweight and high strength

AbstractContinuous plant yarn‐reinforced polylactic acid (PLA) composites were produced through in situ 3D printing, focusing on how plant fiber attributes influence the crystallization, mechanical, and rheological properties of the printed composites. The aim of this study was to assess the viability of plant fibers as substitutes for synthetic ones in engineering additive manufacturing. Plant fibers promoted the crystallization of PLA due to their shear induction and nucleation agent induction effects. The inherent triangular void defect during printing decreased with increasing plant fiber‐volume fraction. Rheological analysis revealed a transition to more elastic behavior post‐fiber addition, indicating solid‐like properties. The tensile strength of flax fiber‐yarn/PLA composite (volume fraction of 50.79%) was 342.37% higher than that of pure PLA, with a 22.2% lower density than pure PLA. Flax fiber demonstrated a superior reinforcement effect than carbon fiber in compressive strength for 3D printed honeycomb sheets with lower energy consumption and footprint. Optimizing fiber characteristics holds promise for high‐performance 3D‐printed natural fiber composites, particularly in vehicle applications.Highlights Plant fiber/polylactic acid (PLA) composites were in situ printed with a volume fraction of 50.79%. Plant fibers promoted the crystallization of PLA during the printing process. The tensile strength of flax fiber/PLA increased by 342.3% with a 22.2% lower density than PLA. Flax fiber showed a better reinforcement than carbon fiber in a compressive test of printed honeycomb.

Characterisation of Miswak (Salvadora persica) Fibre-reinforced Polylactic Acid Composites Prepared by Twin Screw Extrusion

Processing of polymer composites employing fibres from sustainable sources as reinforcement has drastically grown in recent years. This research used Miswak fibres (MF) and polylactic acid (PLA) as the main materials for composite processing. Natural fibres typically include a hydroxyl group (-OH), which makes them hydrophilic. In contrast, the hydrophobic nature of polymer matrices causes them to naturally repel water. This problem was resolved by chemically altering the surface of natural fibres using a 2 wt% sodium hydroxide (NaOH) solution. In this paper, the effect of alkaline treatment has been proven by performing chemical analysis, tensile properties, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to analyse the influence of treated MF content on composite characteristics. The results revealed that biocomposites with modified miswak fibres exhibited better properties than untreated miswak fibres-reinforced polymer biocomposites. Treated MF/PLA composites showed an increase in tensile strength of 52.9% and tensile modulus of 8.16%. From the chemical composition test, lignin composition was reduced from 5.09% to 3.06% and hemicellulose from 28.12 to 10.62% after MF was treated. Meanwhile, thermal properties for both TGA and DSC revealed the elimination of hemicellulose and lignin characteristic peaks, improving the thermal stability of the treated MF/PLA composite. Thus, compared to a pristine sample, the resultant composites' higher mechanical strength and thermal stability demonstrated the significance of chemically treated natural fibres. The novelty of this research is the data on miswak fibre treatment, as no research has been found for this selected treated fibre.

The Effect of the Surface Treatment on TiO2 Particles When Used as a Filler on Crystallization and Mechanical Properties of Polylactic Acid Composites. Case of Study: Silane Coupling Agents and Dicarboxylic Acids Were Used as Surface Modifiers

ABSTRACT This article analyzes the effect of the type of surface modification (using silane coupling agents and dicarboxylic acids) on titanium dioxide particles used as fillers in polylactic acid composites, which were exposed to a photodegradative process. The thermomechanical properties of the composites were analyzed; it was found that the silane coupling agent with Imidazole allowed the composites to have Young’s modulus values 60% lower than the composite without filler. On the other hand, the crystallization rate was 30% higher for composites with azelaic Acid attached to TiO2 particles than for composites without filler at a cooling rate of 5°C min−1. Once degraded composites containing azelaic acid were the least brittle, with a minor increment in Young’s Modulus compared to pure polylactic acid composites. When a mixture of modified titanium dioxide particles (with imidazole and either azelaic acid or pimelic acid) was used, there was a synergistic effect regarding photostability.

A facile method for carbon nanotube/carbon fiber‐reinforced polylactic acid composites

AbstractThe mechanical strength of polylactic acid (PLA) can be improved by carbon fiber (CF) compositing to expand its application in tissue engineering scaffolds. However, the mechanical strength of CF‐reinforced polylactic acid (CFRPLA) composites is compromised due to weak interfacial interaction resulting from the chemically inert surface of CF. In the article, carbon nanotube (CNT) with poly(diallyldimethylammonium chloride) (PDDA) as a coupling agent was covered on CF to improve the chemical activity and roughness of the surface of CF, and then the as‐prepared CF‐PCNT were further incorporated into PLA via melt compounding. The yield strength, modulus, and thermal conductivity of PLA/CF‐PCNT were 14.09%, 7.65%, and 5.24% higher than those of PLA/CF, respectively, and the volume resistivity was 99.74% lower at a 10 wt% loading. The enhancement for the mechanical properties of PLA/CF‐PCNT composites could be ascribed to the mechanical locking, hydrogen bonds and covalent bonds between CF and matrix through the interface modulation of CNT and PDDA. This facile and non‐destructive method offers a novel strategy for the modification of CF fillers.Highlights CF was modified by PDDA and CNT through a facile and non‐destructive method. The active functional groups and roughness on the surface of CF were increased. The surfaces of CFs were characterized by FT‐IR, Raman spectra, XPS and SEM. The interface was improved by mechanical locking, covalent, and hydrogen bonds. The mechanical strength, electrical and thermal conductivity of composites were improved.

Closed-Loop Recycling of 3D-Printed Wood–PLA Composite Parts: Effects on Mechanical and Structural Properties via Fused Filament Fabrication

This study investigated the closed-loop recycling of 3D-printed wood fiber (WF)-filled polylactic acid (PLA) composites via fused filament fabrication (FFF). The WF-PLA composites (WPCs) were extruded into WPC filaments (WPCfs) to produce FFF-printed WPC parts (WPCps). The printed WPCps were reprocessed three times via extrusion and 3D-printing processes. The tensile properties and impact strengths of the WPCfs and WPCps were determined. To further investigate the impact of closed-loop recycling on the surface morphology, crystallinity, and molecular weight of WPCfs, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC), respectively, were used. After closed-loop recycling, the surface morphology of the WPCfs became smoother, and a decrease in the pore sizes was observed; however, the tensile properties (tensile strength and elongation at break) deteriorated. With increasing numbers of recycling iterations, the molecular weight of the PLA matrix decreased, while an increase in crystallinity was observed due to the recrystallization of the low-molecular-weight PLA molecules after recycling. According to the SEM images of the recycled WPCps, their layer heights were inconsistent, and the layers were rough and discontinuous. Additionally, the color difference (ΔE*) of the recycled WPCps significantly increased. Compared with those of the WPCps after recycling them only once, the tensile strength, elongation at break, and impact strength of the WPCps noticeably decreased after recycling them twice. Considering the changes in various properties of the WPCfs and WPCps, the FFF-printed WPC parts can be reprocessed only once through 3D printing.

A promising pullulan/PLA composite: Influence of pullulan in the scaffolds morphology constructed by 3D printing

AbstractManufacturing three‐dimensional scaffolds with significant rough and porous structures is advantageous in tissue regeneration approaches influencing cell growth. Thus, this work aims to study the effect of using different Pullulan contents (PULL) in the poly(lactic) acid (PLA) matrix for 3D printing scaffolds. PLA composites filler with PULL (5 and 10% wt.) were prepared in a thermokinetic mixer, extruded in a machine, and then used to print samples using a fused deposition modeling (FDM) 3D printer. The prepared filaments and scaffolds were characterized using Field emission scanning electron microscopy (FESEM), Fourier‐transform infrared spectroscopy (FTIR), thermogravimetry analyses (TGA), water contact angle (WCA), differential scanning calorimetry (DSC), and hardness techniques. The insertion of PULL into the PLA matrix influenced the increase in diameter and roughness, and density reduction of the composite filaments compared to pristine PLA. Furthermore, the filler promoted an increase in thermal stability, shore hardness, and the development of promising morphological characteristics for cell growth because the walls of the scaffolds are more robust and have more regular‐sized holes. The scaffold fabrication reinforced with 10% PULL presented high surface roughness (up to 1022% if compared with pristine PLA), and open pores can be confirmed successfully compared to pristine PLA. Thus, the use of PULL as a filler in a PLA matrix guarantees the development of composite scaffolds with improved morphological and hardness properties, which could allow the possibility of future research into the application of the proposed material (10% wt. PULL) as an ecologically correct and biocompatible alternative for application in tissue engineering.

Synchronously enhanced flame retardancy and mechanical properties of polylactic acid via in-situ assembly of polyphosphazene nanoparticles on ammonium polyphosphate

Polylactic acid (PLA) exhibits wide potential applications in many fields ranging from textile, packaging material to biomedical devices. However, the relatively low mechanical properties and inflammability are obstacles to the expansion of its application. Here, a kind of polyphosphazene nanoparticles with tannic acid (TA) as template, hexachlorocyclotriphosphazene (HCCP) and 4,4′-Sulfonyldiphenol (BPS) as comonomers were prepared (named as HTB), and then combined with ammonium polyphosphate (APP) to enhance the comprehensive properties of PLA composites. The introduction of HTB strengthened the interfacial adhesion of composites via constructing the hydrogen bond interaction between PLA and APP, promoting the homogenous dispersion of APP in the composite and the formation of APP network. The flame retardant measurements presented that incorporating 10 wt% APP and 5 wt% HTB in PLA increased the limit oxygen index (LOI) value to 31.0% and endowed the composite with the V-0 rating of UL-94 test and simultaneously, the peak of heat release rate (PHRR) and total heat release (THR) of the composite decreased by 14.2% and 13.2% compared with pure PLA. Specially, there was almost no melt drip appeared during the combustion process, which was distinctly different from the combustion behavior of the composite containing only 20 wt% APP with the V-2 rating of UL-94 test. The uniform dispersion of APP in the PLA matrix and the strong interfacial adhesion between APP and the PLA matrix contribute to the enhancement of the mechanical properties of composites, and the elongation at break, Young’s modulus and impact strength of the composite were increased by 52.9%, 7.6% and 24.2%, respectively. The present study offers novel insights for the trade-off between flame retardancy and mechanical properties with PLA composites.

Feasibility of polylactic acid and essential oil composite with insecticidal properties for prevention of Sitophilus oryzae and Oryzophilus surinamensis in Sorghum and Pearl millet

Current study provides insight on the feasibility of polylactic acid (PLA) integrated with (1:1 ratio) of essential oils belonging to Ocimum gratissimum (OG) and Mentha spicata (MS) for prevention of major stored insect pests (Sitophilus oryzae and Oryzophilus surinamensis) in Sorghum and Pearl millet. A combination of OG and MS essential oils (1:1) was incorporated into the PLA polymer matrix. Further, SPME analysis of synthesized PLA showed the presence of volatiles corresponding to carvone (6.44 %) and thymol (6.22 %). Synthesized PLA composites were tested against S. oryzae and O. surinamensis using Sorghum and Pearl millets, and insect mortality was equivalent to commercial super bags (CSB). The head space oxygen decreased significantly in CSB and slightly in PLA bags. Thickness of EO blended PLA composite was increased (99 μm), tensile strength (23.94 MPa), WVTR (1.42 g/m2.hr) analysis, significant folding ability, and swelling capacity (0.24 %) showed slight reduction in composite film. TGA showed good thermal stability (334˚C) and XRD displayed the increased crystallinity (38.35 %) in PLAOM films, SEM and FTIR analysis of the synthesized composite films revealed complete homogenization of EO and PLA matrix. In addition, SEM analysis of insects (control & treated) revealed less topology changes in the elytra. Biodegradability study confirmed the weight loss in PLA films. Hence, current approach of using composite EO's with PLA offers sustainable solution for prevention of infestation during storage of millets.

Enhancing Compatibility and Biodegradability of Polylactic Acid/Biomass Composites Through Torrefaction of Forest Residue

This study investigated the effects of torrefaction on forest residue (FR) and its subsequent application as a bulk-loading filler in polylactic acid (PLA) composites. Torrefaction enhanced the chemical properties of FR, improving its compatibility with PLA, and the crystallinity increased from 24.9% to 42.5%. The process also improved the hydrophobicity of PLA/biomass composites, as demonstrated by the water contact angle of 76.1°, closely matching that of neat PLA (76.4°). With the introduction of 20% modified biomass properties after torrefaction treatment, the tensile strength of PLA/biomass composite increased from 58.7 to 62.3 MPa. Additionally, the addition of torrefied forest residue (TFR) accelerated biodegradation by increasing the onset of degradation and inhibiting crystallization. After 90 d, the biodegradability of PLA/biomass composites reached 94.9%, which had a 6.9% increase compared to the neat PLA (88.8%). Overall, this study highlights the potential of torrefaction in enhancing both the physical properties and biodegradability of PLA-based composites, contributing to a more sustainable approach to reducing plastic pollution.

Mechanical Properties and Flammability Analysis of Wood Fiber Filled Polylactic Acid (PLA) Composites Using Additive Manufacturing

ABSTRACT Natural fibers, such as wood fibers, can substitute for synthetic fibers in various applications due to their low environmental impact, cost-effectiveness, and outstanding mechanical properties as rapid-growing materials and renewable resources. This paper aims to investigate the mechanical properties of 20% wood fiber as a reinforcement material in polylactic acid (PLA) using an additive manufacturing approach. The samples were fabricated using 3D printing techniques. The relevant parameters included the orientation of printing in X, Y, and Z directions, with the percentage of infill set to be 100%. The findings indicated that bio-composites and their adopted printing orientations confirmed the significant effects on the mechanical properties. Pure PLA possessed superior properties in all directions compared to wood/PLA. The highest values were 50.33 MPa for tensile strength and 94.36 MPa for flexural strength, both achieved in Y orientations. However, composites showed an improvement in tensile and flexural moduli in X orientation with 1395.40 MPa, and 2937.72 MPa for Young and flexural modulus, respectively. In the flammability test, wood/PLA bio-composites were ignited easily with reduced smoke production compared to the neat PLA. Wood/PLA bio-composites exhibited high stiffness, and their mechanical properties were influenced by many factors, such as percentage of weight fraction, wood type, and printing orientations.

Evaluation of the Chemical Structure and Thermal Properties of Polyethylene Glycol (PEG)-Doped Polylactic Acid (PLA)/Multiwalled Carbon Nanotube (MWCNT) Composites

This study aimed to investigate the chemical structure, thermal properties, and stability of polylactic acid (PLA) composites blended with multi-walled carbon nanotubes (MWCNTs) and polyethylene glycol (PEG). The composites were fabricated using a masterbatch blending method with two different molecular weights (Mw) of PEG. The masterbatch was initially prepared using solvent casting with chloroform as the solvent, followed by melt blending using an extruder. ATR-FTIR spectroscopy identified strong hydrogen bonds between the C=O groups of PLA and the –OH groups of PEG, as evidenced by the peak at 1748 cm¹. Differential Scanning Calorimetry (DSC) revealed that incorporating 14 wt% of PEG 10,000 into PLA/MWCNT composite significantly enhances the melting enthalpy (∆Hm) from 18.3 J/g to 24.6 J/g and the degree of crystallinity from 2% to 17.3%. The glass transition temperature (Tg) decreased with the addition of PEG, indicating increased chain mobility, while the melting temperature (Tm) remained relatively constant around 158 oC regardless of the PEG Mw. Despite the plasticizing effect of PEG, the thermal stability of the composites was maintained across different PEG Mw. Scanning Electron Microscope (SEM) images showed that MWCNTs were well dispersed within the blend, facilitated by ultrasonic stirring during preparation.

Enhanced rheological, crystallization, mechanical, and heat resistance performance of poly(L‐lactide)/basalt fibers composites via in situ formation of stereocomplex polylactide crystals

AbstractDue to its favorable mechanical strength, transparency, and biocompatibility, polylactic acid (PLA) has considerable potential as a biodegradable material. Nevertheless, developing high‐performance PLA composites through environmentally friendly and cost‐effective methods remains a significant challenge. In this study, the composites comprising poly(L‐lactide) (PLLA), basalt fibers (BFs), and poly(D‐lactide) (PDLA) are prepared through facile melt blending. The in situ formed stereocomplex polylactide (SC‐PLA) crystals improve the crystallization ability and rheological behavior of PLLA/BF/PDLA composites. Upon adding 5 wt% PDLA, BFs are nicely dispersed in PLLA matrix because of increased shear intensity. The synergistic effect of BFs and SC‐PLA crystals enhances the mechanical, thermomechanical, and heat resistance properties of PLLA. In particular, PLLA/BF/10%PDLA composites exhibit a Vicat Softening Temperature (VST) of 155.5°C, increasing by approximately 100°C over neat PLLA. Annealing treatment increases the Young's modulus, thermomechanical properties, and VST of samples while reducing their tensile strength. Interestingly, the tensile strength of the annealed PLLA/BF/10%PDLA composites is 50.2 MPa, twice that of the annealed neat PLLA due to the introduction of SC‐PLA crystals. Simultaneously improving the rheological, mechanical, and heat resistance performance of PLLA opens possibilities for expanding its potential applications in the industrial field.

Tasar silk fiber waste reinforced polylactic acid composite: Physical, mechanical, and sliding wear characterization

Incorporating natural industrial waste as a reinforcement for the development of sustainable composite is now being extensively practiced to eliminate harmful synthetic fiber. This study exhaustively evaluated the potential of tasar silk fiber waste (TSFW) as a reinforcing agent in a polylactic acid (PLA) matrix to optimize the physical, mechanical, and wear properties. Therefore, PLA-based biocomposites with varying TSFW proportions (0, 2, 4, 6, 8, and 10 by weight) are manufactured and then evaluated for physical (density, voids, water absorption), mechanical (tensile, flexural, impact, and hardness), and sliding wear properties. Results suggested that water uptake of PLA composites increases with the addition of TSFW and becomes saturated after nine days of immersion. The TSFW reinforcement at 8 wt% in PLA yields 32 % and 22 % improvement in tensile strength (66.2 MPa) and flexural strength (103.2 MPa), respectively. A remarkable improvement was observed in the impact strength at similar reinforcement (8 wt%) of TSFW with the observed value of 27.90 kJ/m2. A continuous increase in hardness was obtained by including TSFW in PLA, with the highest value of 86 Shore D recorded for 10 wt% TSFW added biocomposite. The specific wear rate of all samples increased, but the incorporation of TSFW significantly reduced the same. Microscopic examination suggests that microploughing, microcutting and groove formations were the main mechanism of material removal. After examining the results, it is recommended that TSFW be used in bidirectional mat form for further enhancement of mechanical properties and improved bonding between fiber and matrix.

Tribology Behavior of In-Situ FDM 3D Printed Glass Fibre-Reinforced Thermoplastic Composites

Fused deposition modeling (FDM) 3D-printed parts are generally weaker compared to injection-moulded parts. Fibre reinforcement is one of the techniques used to enhance the mechanical strength and the tribological behavior of the FDM-printed parts. Recently, a new method for creating FDM 3D-printed composites was developed. Current work focuses on the tribological behavior of the glass fibre-reinforced PLA, manufactured using this new composite manufacturing method. Experiments were conducted to investigate the effect of Glass Fibre (GF) reinforcement on FDM 3D-printed thermoplastic composites, specifically polylactic acid (PLA) under different linear sliding speed and directions. All 3D printed glass fibre-reinforced PLA (PLA-GF) composites exhibited a lower wear rate and a higher friction coefficient compared to 3D printed PLA. Increasing in disc’s linear speed or sliding speed of the pins resulted in a lower coefficient of friction and wear rate. In addition, a perpendicular raster direction towards the disc rotation or pin motion experienced greater friction and greater wear.

Hybrid toughening effect of flax fiber and thermoplastic polyurethane elastomer in 3D‐printed polylactic acid composites

AbstractFlax fiber has emerged as a promising, eco‐friendly alternative to traditional synthetic reinforcement in polymer composites. However, manufacturing biocomposites using three‐dimensional (3D) printing technology is typically accompanied by significant processing challenges and weak product performance under dynamic loading conditions. This study aims to unlock the potential of 3D‐printed polylactic acid (PLA) by incorporating chemically modified chopped flax fibers and thermoplastic polyurethane elastomer to improve impact strength and processability. To achieve this, we employed the fused deposition modeling (FDM) technique to prepare composite specimens for the study. The crystallization behavior, tensile and impact properties, as well as the fracture behavior of the composites were investigated. The findings suggest that our approach stands out because it not only facilitates the challenging task of 3D printing PLA with fiber additives of high weight fraction and high aspect ratio but also results in a remarkable 120% enhancement in impact strength and an around 31.2% increase in tensile elongation compared to neat PLA, without compromising the elastic modulus.Highlights Flax fibers were modified through alkalization and silanization. Alkalization significantly enhanced printing quality. Silanization reduced fiber attrition and doubled the fiber aspect ratio. TPU particles facilitated the 3D printing of biocomposites. For the first time, the hybrid strategy doubled the impact strength of PLA.