Polylactic Acid Fibers Research Articles

Manufacturing and Mechanical Property Evaluations of PLA/Carbon Fiber/Glass Fiber Composites

This study uses carbon fiber (CF) and glass fiber (GF) as reinforcement for polylactic acid (PLA) fiber, and their mixtures are melt-blended into PLA/CF/GF composites. Mechanical properties of the composites are evaluated by applying a tensile test, a flexural test, and an impact test, and the dispersion of fibers is observed by using a scanning electron microscopy (SEM). The test results show that the increasing content of CF results in a greater strength in the composites while the increasing content of GF provides the composites with greater modulus. The combination of both CF and GF contributes to a certain level of mechanical strength and also decreases the production costs for the composites.

Production of bamboo fiber reinforced fibrillated poly(lactic acid) (PLA) material obtained by a papermaking process

A devised beating process was applied, which enabled the formation of slurry consisting of uniformly dispersed fibrillated polylactic acid (PLA) fibers with bamboo fiber, and the polymer material was obtained by a conventional papermaking process. Owing to the fast dewatering time, good repeatability and the facility to manufacture on a large scale, this process was used. It was revealed that the beaten PLA fiber was overall in machinery extrusion by the results of optical microscope and scanning electron microscope (SEM) observations. The improvement in the tensile index, burst index, tear index and other mechanical properties was considered as a key benefit as a result of adding bamboo fiber.

Hemp Made Bio-Composites

Hemp cultivation is one of the possibilities to use agricultural land of Latvia. Mechanical and physical properties of hemp fiber and its chemical structure is suitable for using as a reinforcement, but polypropilene (PP) fibers and PolyLactic Acid (PLA) fibers as a matrix for bio-composites. Compression molding is the most common composite processing technology. Composites with the content of 20 % – 40% of natural fiber could provide optimal mechanical properties. The demand for bio-composites with improved properties will be increasing in the future. Sandwich structure of bio-composite is one of the ways to protect natural fiber from heating degradation.

Accelerated in vitro degradation properties of polylactic acid/phosphate glass fibre composites

Degradation properties were studied for polylactic acid (PLA) and phosphate glass fibre (40P2O5–24MgO–16CaO–16Na2O–4Fe2O3, denoted as P40) reinforced unidirectional (UD) and randomly mat (RM) PLA composites using phosphate buffer saline (PBS) media over a range of temperatures from 21 to 85 °C. Glass transition and melting temperatures for PLA decreased from 61.3 and 167.4 to 52.7 and 151.6 °C, respectively, and crystallinity increased from 9.2 to 58.3 % during 3 days of degradation period in PBS media at 85 °C. Appearance of sharp crystalline peaks after degradation at higher temperatures which was confirmed via X-ray diffraction analysis was also indicative of increase in crystallinity. However, flexural strength decreased by approximately 20 % (for PLA) and by around 50 % (P40 RM and P40 UD composites) of the initial strength after degradation in PBS at 37 °C. No significant changes in mechanical properties were observed before and after degradation of composites at 21 °C for 56 days. Monomodal molecular weight distribution for the PLA before and after degradation in PBS at 37 °C was replaced by bimodal after degradation at higher temperatures. Arrhenius equation applied for the change in molecular weight of the polymer and composite samples and the obtained degradation activation energies were 85.4, 78.7 and 74.1 kJ mol−1 for PLA within PLA alone, P40 RM and P40 UD composites, respectively. Time prediction was applied to correlate short-term degradation (at elevated temperatures) to the long-term effects (at 37 °C) using both ‘tipping point’ and molecular weight as co-ordinates.

Fabrication and properties of microporous metakaolin-based geopolymer bodies with polylactic acid (PLA) fibers as pore generators

This paper reports the synthesis and characterization of a microporous geopolymer body based on metakaolin. Two kaolinites were used as the starting materials in conjunction with sodium silicate and sodium hydroxide and three sizes of polylactic acid (PLA) fibers (12, 20 and 29µm diameter) were used as the pore-forming media. The microporous bodies were formed from geopolymer pastes of optimized composition by extrusion, which yielded bodies with reasonably well-aligned pore-forming fibers which were decomposed by the alkaline conditions during curing and drying of the bodies. XRD, FTIR, 27Al MAS NMR, and SEM were used to characterize the chemistry and microstructure of the porous products and their compressive strengths were also measured. The molar composition SiO2/Al2O3=4 was found to give the best geopolymer characteristics, while the optimal ratio Na2O/Al2O3 which affected the leachability of the PLA fibers and thus the size of the resulting pores, was optimized in the range 1.5–1.75 depending on the kaolinite. Water permeability measurements indicate that the use of PLA fibers as pore-formers significantly increases the permeability of the samples, while the maximum pore size of the porous bodies, determined by bubble point measurements, is related to the size of the particulate matter that could be retained, and indicates that their performance could be tailored for particular filtering applications by adjusting their synthesis parameters.

A novel approach for designing nonwoven hybrid wound dressings: Processing and characterisation

The paper focuses on the development of novel absorbent nonwoven structures by using natural biodegradable carboxymethylcellulose (CMC), alginate and polylactic acid (PLA) fibres. These fibres have been blended and reinforced with synthetic hollow polyester (HPES), polypropylene (PP) and hollow viscose (HV) fibres. The main aim was to enhance the wicking properties of the structures for minimising the pooling of exudate and maceration. It is also aimed to enhance the integrity of structures to minimise the contamination of wounds due to loose fibres. The incorporation of PLA into wound dressings has been attempted for the first time and their functional properties have been studied. The single-fibre, blended and hybrid fabrics have been engineered. The results demonstrate that HPES reinforcement has a critical importance for CMC fabric in terms of wicking properties, tensile properties and air permeability. It has also been demonstrated that the contribution of PLA in the wound dressings is to enhance the properties such as absorbency, wicking, flexural rigidity and air permeability.

Cell patterning on polylactic acid through surface-tethered oligonucleotides

Polylactic acid (PLA) is a candidate material to prepare scaffolds for 3-D tissue regeneration. However, cells do not adhere or proliferate well on the surface of PLA because it is hydrophobic. We report a simple and rapid method for inducing cell adhesion to PLA through DNA hybridization. Single-stranded DNA (ssDNA) conjugated to poly(ethylene glycol) (PEG) and to a terminal phospholipid (ssDNA-PEG-lipid) was used for cell surface modification. Through DNA hybridization, modified cells were able to attach to PLA surfaces modified with complementary sequence (ssDNA′). Different cell types can be attached to PLA fibers and films in a spatially controlled manner by using ssDNAs with different sequences. In addition, they proliferate well in a culture medium supplemented with fetal bovine serum. The coexisting modes of cell adhesion through DNA hybridization and natural cytoskeletal adhesion machinery revealed no serious effects on cell growth. The combination of a 3-D scaffold made of PLA and cell immobilization on the PLA scaffold through DNA hybridization will be useful for the preparation of 3-D tissue and organs.

Oxidative solution polymerization of aniline hydrochloride onto electrospun nanofibers mats of polylactic acid: Preparation method and characterization

ABSTRACT In this work, we present the preparation of polylactic acid (PLLA)/polyaniline (PANI) conductive composite nanofibers mats. They are prepared by bulk oxidative solution polymerization of PANI onto electrospun non‐woven fibers mats of PLLA. The PANI ratio in the composite is about 70%w/w. Scanning electron microscopy (SEM) shows that PLLA nanofibers are randomly oriented, beads free with diameters of 186 ± 85 nm, The PLLA/PANI composite nanofibers diameter values are 518 ± 128 nm with a good adherence between PANI and PLLA nanofibers. DSC and XRD measurements reveal an amorphous structure of the electrospun PLLA fibers due to the rapid evaporization of the solvent. FTIR and UV–vis spectra reflect good mutual interactions between PANI and PLLA chains. The DC‐conductivities ( ) far better than other published ones for similar composites prepared by bulk oxidative solution polymerization of PANI onto other electrospun nanofiber mats or with electrospun nanofibers from a solution mixture of PLLA and PANI. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41618.

Development of cotton-rich/polylactic acid fiber blend knitted fabrics for sports textiles

In this study, the moisture and thermal transmission properties of cotton/polylactic acid-blended knitted fabrics were studied. Cotton and polylactic acid fibers were blended to produce yarns of 14.7 tex (40 s Ne) with two different blend proportions. The yarns were then knitted into plain jersey structures, followed by scouring and bleaching treatments. The produced fabrics were evaluated for dynamic moisture transport properties using SDL Atlas moisture management tester. The moisture vapor transmission rate of developed fabrics was measured using the dish method, and the thermal properties were measured using KES Thermolabo instrument. Results indicate that blending of polylactic acid fibers with cotton fibers improve the moisture management properties of the resultant fabric. The overall moisture management capability values were found to be better for cotton/polylactic acid fiber 65:35 blended fabric. A marginal improvement was observed only in the case of cotton/polylactic acid fiber 80:20 blended fabric. The moisture vapor transmission and air permeability of blended fabrics were also found to be higher than those of 100% cotton fabric. The thermal conductivity, insulation, and warm–cool feel values of blended fabrics range between 100% cotton and 100% polylactic acid fiber fabrics. This type of fabric is more suitable for use as sportswear and active wear.

Appropriate nonwoven filters effectively capture human peripheral blood cells and mesenchymal stem cells, which show enhanced production of growth factors.

Scaffolds, growth factors, and cells are three essential components in regenerative medicine. Nonwoven filters, which capture cells, provide a scaffold that localizes and concentrates cells near injured tissues. Further, the cells captured on the filters are expected to serve as a local supply of growth factors. In this study, we investigated the growth factors produced by cells captured on nonwoven filters. Nonwoven filters made of polyethylene terephthalate (PET), biodegradable polylactic acid (PLA), or chitin (1.2-22 μm fiber diameter) were cut out as 13 mm disks and placed into cell-capturing devices. Human mesenchymal stem cells derived from adipose tissues (h-ASCs) and peripheral blood cells (h-PBCs) were captured on the filter and cultured to evaluate growth factor production. The cell-capture rates strongly depended on the fiber diameter and the number of filter disks. Nonwoven filter disks were composed of PET or PLA fibers with fiber diameters of 1.2-1.8 μm captured over 70% of leukocytes or 90% of h-ASCs added. The production of vascular endothelial growth factor (VEGF), transforming growth factor β1, and platelet-derived growth factor AB were significantly enhanced by the h-PBCs captured on PET or PLA filters. h-ASCs on PLA filters showed significantly enhanced production of VEGF. These enhancements varied with the combination of the nonwoven filter and cells. Because of the enhanced growth factor production, the proliferation of human fibroblasts increased in conditioned medium from h-PBCs on PET filters. This device consisting of nonwoven filters and cells should be investigated further for possible use in the regeneration of impaired tissues.

Novel genipin-collagen immobilization of polylactic acid (PLA) fibers for use as tissue engineering scaffolds.

The material surface plays an important role in the case of biomaterials used as tissue engineering scaffolds. On exposure to a biological environment, extra cellular matrix (ECM) proteins are adsorbed non-specifically onto the surface and cells interact indirectly with the surface through the adsorbed proteins. Most synthetic polymeric biomaterials lack the desirable surface properties for cells as well as have poor cellular adhesion due to their hydrophobic nature. The main objective of this study was to harness surface functionalization technologies to fabricate scaffolds that would be biocompatible and support the adhesion and proliferation of fibroblast cells. The collagen was immobilized on the surface of functionalized PLA via a novel natural cross-linking molecule genipin which resulted in improved cell proliferation of human dermal fibroblasts as compared to the PLA surface coated with collagen without genipin. It is believed that genipin helps reduce steric problems between the functional groups and large protein molecules, and enables immobilized peptide to move more freely in a biological environment.

Antimicrobial metal–organic frameworks incorporated into electrospun fibers

Abstract The objective of this paper is to present a new class of polylactic acid (PLA) fibers containing cobalt-based metal organic frameworks (MOF). The material used was Co-SIM-1, a cobalt-based substituted imidazolate. Composite mats were prepared by electrospinning PLA with a suspension of polyvinylpyrrolidone-stabilized Co-SIM-1. MOF particles formed aggregate of a small number of primary particles that, after electrospun, became completely embedded inside polymeric fibers. The dispersion of particles was better for lower loadings, for which the relative amount of metal released to culture media was also higher. The antimicrobial activity of composite mats was assessed using SEM images, fluorescence microscopy, direct plate reading of fluorescent stains and plate count of colony forming units among other. The microorganisms used in this study were Pseudomonas putida and Staphylococcus aureus. Fluorescence techniques allowed recording viable and damaged cells directly on mat surface and in the culture media embedding the fibers. The results showed higher sensitivity of S. aureus to cobalt-containing fibers, with a reduction in colony forming units of up to 60% with respect to PLA mats. The results also showed the presence of viable but non-culturable microorganisms, which fail to form colonies but yield a positive signal to viable cell staining. Cobalt-based MOF included in electrospun mats provide antibacterial activity suitable to be used to prepare membranes for various biomedical applications.

Effects of adding resorbable phosphate glass fibres and PLA to calcium phosphate bone cements.

Calcium phosphate cements (CPCs), due to their biocompatibility and degradation properties, are being widely investigated as a replacement to more commonly used polymethylmethacrylate (PMMA) for vertebroplasty. CPCs have shown the potential to be replaced by host bone tissue during the healing/remodelling process. However, brittleness and comparatively low strength restrict the use of CPC in load-bearing applications. Although porous CPC can integrate with bone over time, slow degradation profiles and poor interconnectivity between pores restricts osseointegration to the top layer of CPC only. Polylactic acid (PLA) and phosphate glass fibres (PGFs) were incorporated in a CPC matrix to overcome the problem of inherent brittleness and limited osseointegration. Incorporation of PLA and PGFs within CPC was successful in achieving a much less brittle CPC matrix without affecting the mechanical properties of CPC. The area under the stress-strain curve showed that the total energy to failure of the CPC hybrid was significantly greater than that of the CPC control. The methodology adopted here to add PLA within the CPC matrix may also allow for incorporation of PLA cross-linked biochemicals. Micrographic studies revealed that it was possible to confer control over pore size, shape and interconnectivity without negatively affecting the mechanical properties of the cement. This tailorable porosity could potentially lead to better osseointegration within CPC.

Adipose-Derived Stem Cells with the Control Release Vegf Polylactic Acid Fiber Catheters Gelatin Scaffold for Tissue Engineering

ABSTRACT Aim: The major obstacles of autologous fat grafting after surgery for breast cancer were low graft survival and high resorption rate. The purpose of this study was to explore adipose-derived stem cells with a new scaffold could control release vascular endothelial growth factor (VEGF) to promote transplant survival and neovascularization. Methods: Polylactic acid fiber catheters loaded with VEGF were included in a gelatin scaffold produced by freeze crosslinking. The release dose and persistence of VEGF from the tridimensional structures were determined using the enzyme-linked immunosorbent assay (ELISA). Human adipose-derived stem cells (hASCs) were extracted and expanded ex vivo, seeded to the scaffold and cultured to test the biocompatibility using the WST-1 assay. Three days after co-cultured with hASCs, the scaffolds were transplanted to the back of nude mice, the control groups were only inject hASCs, transplanted control scaffold with hASCs. Three months later, transplants volume and histology were evaluated and neovascularization was determined by the quantity of capillary and the positive of endothelial cell marker CD31 in immunohistochemistry. Results: The tridimensional structures could release VEGF stable and durable, which had no significant cytotoxicity on hASCs. The transplants volume and the capillary quantity of hASCs with the control release VEGF polylactic acid fiber catheters gelatin scaffold group was significantly larger than other two groups. Immunohistochemistry analysis revealed the transplants were rich in CD31-positive cells. Conclusions: Adipose-derived stem cells together with the control release VEGF polylactic acid fiber catheters gelatin scaffold could significantly promoted vasculogenesis and reduced absorption and necrosis after transplant. Disclosure: All authors have declared no conflicts of interest.

Evaluation and Measured Analysis by FTIR of Fiber Insulation Materials Used in Inflatable Mini Cold Storage

Thermal insulation performance is a key factor in evaluation of thermal insulation materials. The chemical structure of polyester fiber, bamboo fiber and polylactic acid fiber was analyzed, and thermal insulation properties of the samples were investigated in terms of the measured transmittance of IR with before and after treated. The results showed that the measured transmittance of IR of corn fiber was lower than polyester fiber and bamboo fiber. In addition, the measured transmittance of bamboo fiber changed obviously, polyester fiber had small changes, polylactic acid fiber almost had no change. Moreover, the measured transmittance had an increasing trend. The heat preservation performance decreased after the samples were treated.

Repair of Achilles tendon defect with autologous ASCs engineered tendon in a rabbit model

Adipose derived stem cells (ASCs) are an important cell source for tissue regeneration and have been demonstrated the potential of tenogenic differentiation in vitro. This study explored the feasibility of using ASCs for engineered tendon repair in vivo in a rabbit Achilles tendon model. Total 30 rabbits were involved in this study. A composite tendon scaffold composed of an inner part of polyglycolic acid (PGA) unwoven fibers and an outer part of a net knitted with PGA/PLA (polylactic acid) fibers was used to provide mechanical strength. Autologous ASCs were harvested from nuchal subcutaneous adipose tissues and in vitro expanded. The expanded ASCs were harvested and resuspended in culture medium and evenly seeded onto the scaffold in the experimental group, whereas cell-free scaffolds served as the control group. The constructs of both groups were cultured inside a bioreactor under dynamic stretch for 5 weeks. In each of 30 rabbits, a 2 cm defect was created on right side of Achilles tendon followed by the transplantation of a 3 cm cell-seeded scaffold in the experimental group of 15 rabbits, or by the transplantation of a 3 cm cell-free scaffold in the control group of 15 rabbits. Animals were sacrificed at 12, 21 and 45 weeks post-surgery for gross view, histology, and mechanical analysis. The results showed that short term in vitro culture enabled ASCs to produce matrix on the PGA fibers and the constructs showed tensile strength around 50 MPa in both groups (p > 0.05). With the increase of implantation time, cell-seeded constructs gradually form neo-tendon and became more mature at 45 weeks with histological structure similar to that of native tendon and with the presence of bipolar pattern and D-periodic structure of formed collagen fibrils. Additionally, both collagen fibril diameters and tensile strength increased continuously with significant difference among different time points (p < 0.05). In contrast, cell-free constructs failed to form good quality tendon tissue with fibril structure observable only at 45 weeks. There were significant differences in both collagen fibril diameter and tensile strength between two groups at all examined time points (p < 0.05). The results of this study support that ASCs are likely to be a potential cell source for in vivo tendon engineering and regeneration.

Biodegradation of polylactic acid (PLA) fibers using different enzymes

The biodegradability of polylactic acid (PLA) nonwovens was evaluated using enzymatic degradation. To evaluate enzyme biodegradation, three enzymes, lipase, esterase, and alcalase, which are known to hydrolyze PLA effectively, were selected. Degradation time was determined under optimal enzyme treatment conditions. Enzymatic degradation affected the width and thickness of PLA nonwovens. In addition, the degree of crystallinity of the PLA nonwovens increased with time for the first 21 days of enzyme biodegradation and then decreased. Alcalase was more efficient than lipase and esterase in degrading the PLA nonwovens. Degradation was found to create cracks on the fiber surface, making the fibers rough. Weight loss and change in tensile strength were not significant, and the observed changes could be due to the cracks on the surface. Our findings propose the mechanism of enzymatic degradation of PLA nonwovens, which might be useful for waste management in the textile industry.

Effect of cellulose nanowhiskers on surface morphology, mechanical properties, and cell adhesion of melt-drawn polylactic Acid fibers.

Polylactic acid (PLA) fibers were produced with an average diameter of 11.2 (± 0.9) μm via a melt-drawing process. The surface of the PLA fibers was coated with blends of cellulose nanowhiskers (CNWs) (65 to 95 wt %) and polyvinyl acetate (PVAc). The CNWs bound to the smooth PLA fiber surface imparted roughness, with the degree of roughness depending on the coating blend used. The fiber tensile modulus increased 45% to 7 GPa after coating with 75 wt % CNWs compared with the uncoated PLA fibers, and a significant increase in the fiber moisture absorption properties at different humidity levels was also determined. Cytocompatibility studies using NIH-3T3 mouse fibroblast cells cultured onto CNWs-coated PLA surface revealed improved cell adhesion compared with the PLA control, making this CNW surface treatment applicable for biomedical and tissue engineering applications. Initial studies also showed complete cell coverage within 2 days.

Manufacturing Technique and Property Evaluations of Tubular PLA/Spandex/Gelatin Composite Braids

Polylactic acid (PLA) is a synthetic polymer that has biocompatibility and biodegradation. This study aims to examine the influence of manufacturing parameters on the physical properties of tubular PLA/Spandex/Gelatin composite braids. PLA fibers and spandex are combined, braided and then immersed in gelatin solution to form tubular PLA/Spandex/Gelatin composite braids. The tensile strength, bursting strength, and porosity of the resulting braids are tested, and the experiment results show that a greater twist per inch (T.P.I.) causes a higher tensile strength and bursting strength, but does not change the porosity distinctively.

Tencel&lt;sup&gt;®&lt;/sup&gt;/Low-Melting-Point Polylactic Acid Composite Nonwoven Fabrics: Manufacturing Technique and Property Evaluations

This study combines hydrophilic and soft Tencel®fibers and low-melting-point polylactic acid (LMPLA) fibers by needle-punching and hot press processes to form moisture-retentive and comfortable Tencel®/LMPLA composite nonwoven fabrics. Air permeability, water vapor transmission rate, softness, water content rate, and water loss rate tests are performed on the composite nonwoven fabrics. The experiment results show that when hot pressed at 130 and 150 °C, the Tencel®/LMPLA composite nonwoven fabrics have good water absorption, water retention, and softness, which can be concluded as successfully moisture-retentive and comfortable Tencel®/LMPLA composite nonwoven fabrics.