Polylactic Acid Fibers Research Articles

Surface Treatment of Polylactic Acid Fiber by Starch Nanocrystals and Interface Modification of Polylactic Acid Fiber-Reinforced Starch Composites

The surface of polylactic acid fiber (PLAF) was treated with self - manufactured starch nanocrystals (SNCs) to improve its interfacial adhesion with the starch matrix. Determination of optimum dispersion conditions of SNCs dispersion by transmittance. The effects of direct oscillatory deposition, chemical grafting SNCs modification, and SNCs dispersion concentration on the surface treatment effect of PLAF and its interfacial bonding with starch matrix were investigated. The results showed that the SNCs were successfully introduced into the PLAF surface, moreover, the modifying effect of the chemical grafted SNCs was better than the direct oscillatory deposition, the distribution of SNCs particles was more uniform on the fiber surface, strong chemical bonding to the fiber surface, make up for the surface damage of the fibers caused by aminolysis. At the SNCs dispersion concentration of 10 g/L, the PLAF tensile strength could be maintained at 582 MPa, a large amount of starch was evenly attached to the surface after pulling out. It showed that a strong interface bond with the starch matrix, the highest IFSS value was 2.57 MPa and the increase was by about 63 %. Therefore, the introduction of SNCs for interfacial modification of PLAF is of great significance and deserves further exploration.

Investigation of Fused Deposition Modelling Process Parameters in 3D Printing for Composite Material (Poly Lactic Acid and Banana Fibre)

Additive manufacturing is gaining popularity nowadays due to its applications in the automotive, medical, aerospace industries, and sports to manufacture complex parts. Fused deposition modelling is an additive manufacturing process utilised widely due to its lower cost, fast prototyping and faster production time. The present study focuses on applying FDM to the composite material filament and the impact of parameters of FDM on the part quality. A composite filament material was prepared to combine PLA (Poly-lactic Acid) and banana fibre. Specimens were prepared using this composite filament by varying various parameters such as layer thickness, infiltration and build orientation. Flexural and tensile tests were performed as per standards. It was found that the material properties considered are significantly affected by percentage infill and build orientation. The ‘on edge’ build orientation provides better material properties as compared to the other two orientations. The tensile strength is observed to be 73% and 77% more in flat orientation and ‘on edge’ orientation, respectively, as compared to upright orientation. Also, the flat orientation and ‘on edge’ orientation respectively showed 60% and 70% more flexural strength than the upright orientation.

Scalable Preparation of Complete Stereo-Complexation Polylactic Acid Fiber and Its Hydrolysis Resistance.

Due to their high sensitivity to temperature and humidity, the applications of polylactic acid (PLA) products are limited. The stereo-complexation (SC) formed by poly(L-lactic acid) (PLLA) and its enantiomer poly(D-lactic acid) (PDLA) can effectively improve the heat resistance and hydrolysis resistance of PLA products. In this work, the blended melt-spinning process of PLLA/PDLA was carried out using a polyester fiber production line to obtain PLA fiber with a complete SC structure. The effects of high-temperature tension heat-setting on the crystalline structure, thermal properties, mechanical properties, and hydrolysis resistance were discussed. The results indicated that when the tension heat-setting temperature reached 190 °C, the fiber achieved an almost complete SC structure, and its melting point was 222.5 °C. An accelerated hydrolysis experiment in a 95 °C water bath proved that the SC crystallites had better hydrolysis resistance than homocrystallization (HC). The monofilament strength retention rate of SC-190 fiber reached as high as 78.5% after hydrolysis for 24 h, which was significantly improved compared with PLLA/PDLA drawn fiber.

Electrospun Polylactic Acid-Based Fibers Loaded with Multifunctional Antibacterial Biobased Polymers.

Here, we report the development of antibacterial and compostable electrospun polylactic acid (PLA) fibers by incorporation of a multifunctional biobased polymer in the process. The multifunctional polymer was synthesized from the bio-sourced itaconic acid building block by radical polymerization followed by click chemistry reaction with hydantoin groups. The resulting polymer possesses triazole and hydantoin groups available for further N-alkylation and chlorination reaction, which provide antibacterial activity. This polymer was added to the electrospinning PLA solution at 10 wt %, and fiber mats were successfully prepared. The obtained fibers were surface-modified through the accessible functional groups, leading to the corresponding cationic triazolium and N-halamine groups. The fibers with both antibacterial functionalities demonstrated high antibacterial activity against Gram-positive and Gram-negative bacteria. While the fibers with cationic surface groups are only effective against Gram-positive bacteria (Staphylococcus epidermidis and Staphylococcus aureus), upon chlorination, the activity against Gram-negative Escherichia coli and Pseudomonas aeruginosa is significantly improved. In addition, the compostability of the electrospun fibers was tested under industrial composting conditions, showing that the incorporation of the antibacterial polymer does not impede the disintegrability of the material. Overall, this study demonstrates the feasibility of this biobased multifunctional polymer as an antibacterial agent for biodegradable polymeric materials with potential application in medical uses.

Correction of large jawbone defect in the mouse using immature osteoblast-like cells and a 3D polylactic acid scaffold.

Bone tissue engineering has been developed using a combination of mesenchymal stem cells (MSCs) and calcium phosphate-based scaffolds. However, these complexes cannot regenerate large jawbone defects. To overcome this limitation of MSCs and ceramic scaffolds, a novel bone regeneration technology must be developed using cells possessing high bone forming ability and a scaffold that provides space for vertical bone augmentation. To approach this problem in our study, we developed alveolar bone-derived immature osteoblast-like cells (HAOBs), which have the bone regenerative capacity to correct a large bone defect when used as a grafting material in combination with polylactic acid fibers that organize the 3D structure and increase the strength of the scaffold material (3DPL). HAOB-3DPL constructs could not regenerate bone via xenogeneic transplantation in a micromini pig alveolar bone defect model. However, the autogenic transplantation of mouse calvaria-derived immature osteoblast-like cells (MCOBs) isolated using the identical protocol for HAOBs and mixed with 3DPL scaffolds successfully regenerated the bone in a large jawbone defect mouse model, compared to the 3DPL scaffold alone. Nanoindentation analysis indicated that the regenerated bone had a similar micromechanical strength to native bone. In addition, this MCOB-3DPL regenerated bone possesses osseointegration ability wherein a direct structural connection is established with the titanium implant surface. Hence, a complex formed between a 3DPL scaffold and immature osteoblast-like cells such as MCOBs represents a novel bone tissue engineering approach that enables the formation of vertical bone with the micromechanical properties required to treat large bone defects.

Electrospun polylactic acid scaffolds with strontium- and cobalt-doped bioglass for potential use in bone tissue engineering applications.

The development of nanoscale biomaterials associated with polymers has been growing over the years, due to their important structural characteristics for applications in biological systems. The present study aimed to produce and test polymeric scaffolds composed of polylactic acid (PLA) fibers associated with a 58S bioglass doped with therapeutic ions for use in tissue engineering. Three 58S Bioglass was obtained by the sol-gel route, pure and doped with 5% strontium and cobalt ions. Solutions of 7% PLA was used as control and added the three different bioglass, 4% of 58S bioglass (PLA-BG), 4% bioglass-doped strontium (PLA-BGSr) and 4% bioglass-doped cobalt (PLA-BGCo). Scaffolds were produced through electrospinning process, and was characterized chemical and morphologically. The in vitro tests were performed using mesenchymal cells cultures from femurs of nine rats, grown in osteogenic supplemented total culture medium. After osteoblastic differentiation induction cell viability, alkaline phosphatase activity, total protein content quantification, and visualization of mineralization nodule tests were performed. Analysis of normal distribution used the Shapiro-Wilk test (nanofibers diameter and biological assay). Data were compared using the Kruskal-Wallis nonparametric test (p= 0.05). The bioglasses produced proved to be free of nitrate, chlorinated and nano-sized, with effective incorporation of therapeutic ions in their structure. All materials showed cell viability (>70%), total protein production, and alkaline phosphatase activity. It was possible to develop polylactic acid scaffolds associated with 58S bioglass doped with therapeutic ions without cytotoxicity. Scaffolds characteristics appear to sustain its application in bone tissue engineering.

Development and characterization of laminated fiber reinforced bio-Composite From nettle and poly lactic acid fiber

Nettle and Poly Lactic Acid (PLA) fibers are the strongest and best fibers with valuable potential as reinforcement in a composite. In this study, the development and characterization of a multi-layered laminated fibre reinforced bio-composite from nettle and PLA fiber were performed. Prior to molding, the nettle fibers were treated with chemicals such as Alkali and silane and the influence of chemical treatment on the property of nettle fibers were investigated. The characteristics of raw and chemically treated nettle fibers were investigated through chemical composition analysis, mechanical properties, Fourier transform infrared spectroscopy, scanning electron microscopy and water sorption test. Furthermore physical and mechanical properties of the nettle/PLA bio-composite have been analyzed. Twenty (20) samples of treated and untreated nettle fiber and five samples of nettle/PLA fiber reinforcement bio-composites were tested and the results were averaged for comparison with one another. Based on the results obtained, the treated fiber improves tensile strength, has a more uniform and smaller diameter, a clean surface, and has a good appearance compared to untreated fiber. Laminated bio-composites were found to increase initially with the increase of nettle fiber content till 50 weight % and decrease afterwards. Generally, the bio-composite prepared with an equal weight proportion of nettle and poly lactic acid fiber obtained better mechanical properties and tensile strength. Water sorption test results showed that water uptake ability of treated nettle fibers were lower than raw nettle fibers.

Poly-lactic acid and carbon fibers 3D printed bars for seismic retrofitting RC beam-to-column joints subjected to elevated temperature

This research proposes novel three-dimensional (3D) printed bars for seismic repairing RC beam-to-column joints subjected to elevated temperatures. A total of eight joint specimens were subjected to a high temperature of 900˚C for 3 h and then exposed to cyclic loading. An experimental program was conducted to retrofit the joints using near-surface mounted (NSM) 3D printed bars adopting several strengthening configurations. Finite element models were then developed using a commercially available code, and a comparison was made between the experimental, analytical, and numerical results. Test results showed that NSM 3D printed bars are highly recommended for retrofitting RC members subjected to cyclic loading. The 3D printed bars made using poly-lactic acid (PLA) and 20% of carbon fibers considerably increased the ductility and drift ratio of the heat-damaged RC joints up to 206% and 216%, respectively. They also increased the load capacity of the joints up to 51%. The load-carrying capacity of the retrofitted joints was then predicted based on the ACI formulations with a proposed empirical factor for calculating the effective strain values of the 3D printed bars.

Development of biodegradable tri-blended fabrics with improved moisture management properties using cotton/polylactic-acid/bamboo-viscose fibres

The influence of fibre blend composition on the moisture management properties of tri-blended cotton-rich knit fabrics with biodegradability has been studied. The cotton, polylactic acid and bamboo-viscose fibres are blended to produce yarns of 14.7 tex (40s Ne) with four different blend proportions, namely 60/20/20, 50/30/20, 50/20/30 and 40/30/30. The yarns are then knitted into a single jersey structure of 130-135 gsm, followed by its scouring, bleaching and relaxation treatments. The relaxed fabrics are then evaluated for dynamic moisture transport properties using the SDL Atlas moisture management tester. The moisture management test results indicate that blending polylactic acid fibres with cotton and bamboo-viscose fibres improves the blended fabric's moisture management properties. The overall moisture management capability value is found to be better for cotton/polylactic-acid/bamboo-viscose blended fabric in the proportion of 50/30/20.

Chitosan nanoparticles encapsulated into PLA/gelatin fibers for bFGF delivery

Abstract Electrospinning is a trendy method because of the ease of use and the high surface-to-volume ratio. The mechanical and biological properties of polylactic acid (PLA) make it one of the most enticing polymers. Gelatin and PLA together are thought to enhance cellular behavior and hydrophilicity of scaffolds. Furthermore, chitosan nanoparticles (CNPs) can be incorporated into PLA fibers to achieve controlled growth factor release. This study utilized PLA–gelatin nanofibrous scaffolds in which CNPs were encapsulated within PLA fibers to achieve a controlled release of basic fibroblast growth factor (bFGF). To produce CNPs, a simple ionic gelation reaction was used. The optimal diameter of CNPs was determined by investigating chitosan to tricalciumphosphatesodium (TPP) ratio and TPP concentration. Using a spectrophotometer, we measured the release rate of bFGF from CNPS and scaffolds. Images from a scanning electron microscope (SEM) were used to assess the effect of various concentrations of PLA and gelatin on fiber diameter. The results showed that PLA–gelatin scaffolds could stimulate the release of growth factors and promote cell proliferation. Using a two-jet electrospinning device to produce PLA–gelatin fibers in combination with CNPs incorporated within PLA fibers to release the bFGF growth factor is the novelty of this study.

Extraction of Natural Dyes from Turmeric (Curcuma longa) and their Application on Polylactic Acid Fiber

This research presents an eco-friendly approach towards Response Surface Methodology (RSM). The current study is based on the optimization of the dyeing process of biodegradable polylactic acid (PLA) fiber using with natural dyes of turmeric extractions by using Soxhlet extraction technique. The dyeing process was carried out by using Daelim Starlet III, which is an infrared dyeing machine. Three independent variables were selected, including pH, time, and temperature. According to the standard test protocols, dyed samples were evaluated for color strength (K/S), CIELab values, fiber tenacity, and fiber elongation. ANOVA test results of the Linear Model exhibited that the model terms have a significant effect on K/S and the physical strength of fiber. Moreover, the observed values were in agreement with the predicted values and the suggested equation model was satisfactory and accurate. A temperature of 100 °C with pH 5 and time duration of 30 minutes in the dyeing process were observed to achieve optimum dyed PLA fibers, exhibiting appreciable strength and elongation. Lastly, dyed fibers exhibited satisfactory color fastness ratings.
 Index Terms: color strength, exhaustion, natural dyeing, polylactic acid fiber, turmeric

Novel mosquito repellent fiber mat containing nepeta essential oil prepared by coaxial electrospinning

AbstractNepeta essential oil (NEO) is considered to have good mosquito repellent properties, the poor stability of which limits the application. This work was aimed at using coaxial electrospinning technology to wrap NEO into Polylactic acid (PLA) fibers to extend the service life of NEO. Under the best test conditions, NEO load capacity (LC) and encapsulation efficiency (EE) is (20.20 ± 0.35%) and (84.18 ± 1.46%), respectively. According to morphology analysis, the concentration of PLA solution and the flow rate of NEO will affect the morphology and properties of the fibers, and the minimum average diameter of the obtained fibers is 740 nm. Release test indicates that using coaxial electrospinning technology can significantly slow down the NEO release rate, in the mosquito avoidance test, the coaxial fiber mat maintained about 80% mosquito repellent rate within 72 h, which is superior to the commercially available N,N‐diethyl‐3‐methylbenzamide (DEET) repellent, indicating its potential in the field of mosquito repellent.

Mechanical properties of 3D printed micro‐nano rice husk/polylactic acid filaments

AbstractIn this study, micro‐nano rice husks (MNRH) fibers are compounded in polylactic acid (PLA) to produce 3D‐printed filaments by using melt blending method, and some properties of the printed samples of different surface treatment processes are measured. Two silane coupling agents of KH550 and KH570 are severally used on MNRH and PLA to mitigate the surface quality deficiencies for an intimate interfacial bond. Microstructural analysis shows that the MNRH fibers of the composites treated by silane coupling agent have a better dispersing performance. Fourier transform infrared illustrates that the KH550 and KH570 are successfully grafted onto PLA and MNRH fibers. Thermogravimetric analysis (TGA/DSC) suggests that the thermostability and crystallinity of the composites treated by silane coupling agents are enhanced. Water absorption experiments shows that the water resistance of the composites is greatly increased by KH550 and KH570. In comparison with pure PLA, the tensile strength, tensile modulus, bending strength and bending modulus of the 6 wt.% MNRH/PLA composites that treated by KH550 and KH570 are enhanced by 83%, 98%, 54%, and 61%, respectively. The composites treated by KH550 and KH570 demonstrates the best performance, suggesting that they have great potential for use as an environmentally friendly alternative material in automotive interiors.

Electrophysiological Recordings from Embryonic Mouse Motoneurons Cultured on Electrospun Poly-Lactic Acid (PLA) and Polypyrrole-Coated PLA Scaffolds.

Background:Biomaterials used as cell growth stimulants should be able to provide adequate cell adhesion with no alteration in cell function. In this work, we developed a 3D model of mouse spinal cord motoneurons on scaffolds composed of electrospun PLA fibers and plasma-polymerized PPy-coated PLA fibers. Methods:The functionality of the cultured motoneurons was assessed by evaluating both the electrophysiological response (i.e., the whole-cell Na+ and K+ currents and the firing of action potentials) and also the expression of the VAChaT by immunostaining techniques. While the expression of the VAChaT was confirmed on motoneurons cultured on the fibrous scaffolds, the electrophysiological responses indicated Na+ and K+ currents with lower amplitude and slower action potentials when compared to the response recorded from spinal cord motoneurons cultured on Poly-DL-Ornithine/Laminin- and plasma-polymerized PPy-coated coverslips.Results:From a morphological viewpoint, motoneurons cultured on PLA and PPy-coated PLA scaffolds did not show the development of dendritic and/or axonal processes, which were satisfactorily observed in the bidimensional cultures.Conclusion:We hypothesize that the apparently limited development of dendritic and/or axonal processes could produce a deleterious effect on the electrophysiological response of the cells, which might be due to the limited growth surface available in the fibrous scaffolds and/or to an undesired effect of the purification process.

Flexible highly-sensitive humidity sensor based on CGO/SMPLAF for wearable human skin humidity detection

Conventional humidity sensors have poor flexibility and low sensitivity, which makes them difficult for wearable electronic device applications. This study aims to fabricate a flexible, high-sensitivity and breathable humidity sensor for skin humidity monitoring. The sensor includes two parts, i.e., shape memory polylactic acid fiber (SMPLAF) as the substrate and crumpled graphene oxide (CGO) membrane as the top humidity-sensitive layer. SMPLAF was firstly stretched and then heated to restore its original shape to obtain the CGO membrane. The unique crumpled morphology of CGO membrane provides a large specific surface area and high capillary force, which facilitates the rapid exchange of water molecules between the sensing CGO membrane and the external environment. Accordingly, the sensor exhibits excellent humidity sensitivity, fast response time (<5 s) and long term stability (15 days). Moreover, the CGO-based sensor demonstrates excellent flexibility. Bent at 120°, the response almost unchanged, whereas the response of the sensor without CGO decreased from 0.89 to 0.66. Though the sensor has the disadvantage of unstable performance at high RH, it could be overcome by controlling the wavelength of the crumpled structure of CGO. Due to the above superior properties, the sensor shows promising potentials for human breath monitoring and skin humidity test.

Effect of surface treatment of cotton fibers on the durability of polylactic acid/cotton-fiber biocomposites

Composites composed entirely of biodegradable polymer materials such as polylactic acid (PLA) and natural fibers are attracting attention as alternatives to petroleum-based plastic materials. Since fibers have low dispersibility in bulk resins such as PLA, the use of fiber surface treatment agents can improve the fiber dispersibility and the physical properties of the composites. In this study, accelerated degradation tests were conducted at 60°C for upto 2000 h on specimens containing cotton fibers at a ratio of 40 wt% to the PLA matrix. The results showed that the interfacial adhesion between the PLA matrix and cotton fibers could be improved by coating the cotton fibers with a reactive surface treatment agent. Furthermore, the addition of 5 wt% of epoxidized linseed oil, a medium-molecular-weight reactive surface treatment agent, not only promoted the crystallization of the PLA/cotton-fiber composites at 60°C, but also improved the thermal and mechanical properties with the degradation time.

Thermal and morphological analysis of various 3D printed composite honeycomb cores

Fused deposition modeling (FDM) was employed to manufacture honeycomb core structures using polylactic acid (PLA) and short carbon fiber (CF) filled PLA composite filaments. For honeycomb structures, circular, square and hexagonal cores were manufactured to explore geometric effects on 3D printing quality. Various physical, thermal and compressive properties for their morphological features were holistically investigated. A comprehensive void analysis was also presented using optical microscopy, scanning electron microscopy (SEM) and X-ray computed tomography (XCT). Thermal analysis using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) was also performed on honeycomb cores. It was manifested that material porosity was dependent on the structure, and had an inverse relationship with compressive properties. Hexagonal core structures especially possessed the lowest amount of material porosity with highest compressive strength relative to circular and square cores. It was also shown that XCT could be employed to estimate the microporosity within the structure, and further could be a useful tool to study the effect of filler addition in the matrix. In this study it was revealed via XCT that PLA/CF composite honeycomb cores yielded lower compressive properties compared to neat PLA structures owing to a large amount of microporosity generated in 3D printing process.

Layer-by-Layer Pirfenidone/Cerium Oxide Nanocapsule Dressing Promotes Wound Repair and Prevents Scar Formation

An increase in the levels of reactive oxygen species (ROS) and high expression levels of transforming growth factor-β (TGF-β) in wound tissue are two major problems for wound repair and scar inhibition. Modulation of the wound microenvironment is considered to be able to overcome these issues. Two possible solutions include the use of cerium oxide nanoparticles (CeO2) as an enzyme-like ROS scavenger and pirfenidone (PFD) as an anti-fibrotic drug to inhibit the expression of TGF-β. However, CeO2 is easily adsorbed by biological macromolecules and loses its enzyme-like activity. Furthermore, the intracellular delivery of PFD is difficult. Herein, the layer-by-layer method was used to prepare nanocapsules (NCs) with a sophisticated structure featuring PFD at their core and CeO2 in their shell; these NCs were referred to as PFD/CeO2 NCs. PFD/CeO2 NCs were supposed to efficiently achieve intracellular delivery of PFD and successfully scavenged ROS from the microenvironment. Cellular experiments verified that PFD/CeO2 NCs had good biocompatibility, satisfactory cellular uptake, and favorable ROS-scavenging capacity. To be applied directly to the wound, PFD/CeO2 NCs were then adhered to plasma-etched polylactic acid (PLA) fiber membranes to prepare a new wound dressing. Animal experiments further demonstrated that the dressing accelerated the epithelialization of the wound, reduced the levels of ROS and TGF-β, improved the arrangement and proportion of collagen fibers, and finally, achieved satisfactory wound-repairing and anti-scarring effects. These results provide a new concept for promoting wound repair and preventing scar formation.

Preparation and properties of nano-SiO2/lipase/polycaprolactone composite microsphere and its application in controlling the degradation of polylactic acid fiber membrane

Polylactic acid (PLA) fiber membrane needs to match the wound healing time when used as a medical adhesive membrane. In order to adjust the degradation cycle of PLA fiber, the composite microspheres of nano-SiO2/lipase/polycaprolactone (PCL) with degradation regulation function were designed and prepared. And then the composite microspheres were added into PLA fiber membrane to verify the degradation regulation function. The results showed that: the optimal preparation process of microspheres was obtained as follows: 5 mg/mL SiO2/lipase complex concentration, 10 mg/mL PCL concentration, 1000 r/min emulsification speed and 600 r/min curing speed. The amount of enzyme, loading in the microspheres, can be regulated in the range of 10.24%–11.29%. And the drug-loaded microspheres had a good sustained release effect. Finally, it was verified that the microspheres could accelerate the degradation rate of PLA fiber membrane.

Four-dimensional design and programming of shape-memory magnetic helical micromachines

Diversified complex tasks put forward higher requirements on shape transformation abilities of magnetic microrobots. Shape memory polymers (SMPs) with desirable properties are ideal options for the development of microrobots. However, programming shape transformations for such small SMP robotic structures is still difficult. Here, a parametric design and programming method is reported for shape-memory magnetic helical micromachines. Through twice mechanically winding and annealing of UV lithography-modified ribbon-like polylactic acid fibers, the customization of permanent and temporary shapes of shape-memory helical micromachines was realized. Expected recoveries of helical micromachines from temporary shapes to permanent shapes were exhibited in response to thermal stimuli, showing diversified shape changes in helix angle, taper angle, length, diameter, and even chirality. Helical micromachines demonstrated controlled locomotion ability under rotating magnetic fields. Through dynamic design and shape programming, acceleration and direction reversal of swimming helical micromachines can be activated by environmental stimuli. Moreover, programmable shape-memory micro-components can be used to fabricate complex multi-component micromachines. This study provided an approach to overcome the programming difficulty of SMP microrobots. The shape-memory magnetic helical micromachines with programmable shape transformations and locomotion ability have great potential in various applications.