PLA Fibers Research Articles

Biodegradable performance of PLA stents affected by geometrical parameters: The risk of fracture and fragment separation

Biodegradable endovascular stents have been claimed to be reliable candidates for implantation devices used in treating cardiovascular diseases since they reduce the long-term side effects on the human biological system. It is aimed in this study to investigate the effect of geometrical parameters on the degradation behavior of poly (lactic acid) stents in term of strut fracture and fragment separation. In this regard, various structural geometry of the PLA stents was simulated in a stenosed artery using finite element method. For predicting the PLA degradation, a computational model was prepared by which the influence of stents design on their radial strength and fracture was investigated. Using a laboratory-scale designed bioreactor, the PLA fibers degradation was evaluated to calibrate the material parameters and verify the simulation method. Simulation results demonstrated that the geometrical parameters, i.e., number of struts, curves radius and stent cells shape, strongly affect the degradation behavior. The results indicated that the smooth design leads to uniform degradation in the whole stent and decreases the danger of stent fragments separation. It was shown that the maximum degradation rate of the stents with rounded curves was one-third of the models with sharp corners.

Effect of BaTiO3 on the aging process of PLA fibers obtained by centrifugal spinning

This study focused on the fabrication of a composite of polylactic acid fibers reinforced with barium titanate (BT) and obtained by centrifugal spinning. Different concentrations of inorganic powder (5, 10, and 15 wt%) have been added to the polymeric solution and the samples have been studied to monitor any modification in chemical, morphological, thermal, and mechanical properties. Subsequently, samples have been subjected to UV/O3 irradiation at two different times (5 and 10 min) with the aim to verify the resistance to aging, which is considered a key factor for medical applications and outdoor. The presence of BT influenced strongly the structure of the fibers in many aspects. Samples with the lowest amount of BT showed a clear decrease of chemical and consequently of mechanical properties manifested with the breakage of the fibers subjected to treatment. The other composites apparently showed similar chemical properties comparing with the one without fillers but the mechanical properties clearly decreased. However, what emerged from the study is a clear stability during the aging tests promoted by the presence of BT. The samples with 10 and 15 wt% of BT presented chemical, thermal, and mechanical stabilities differently from the other samples. These results suggested that the fillers clearly modified the degree of crystallinity acting as nucleation agents and promoting the development of a stable crystalline phase during the treatment.

Bikomponent ve Karışım HDPE/LDPE Filamentlerin Üretimi ve 3B Yazıcılarda Kullanımı

Thermoplastic polymer have been used in 3D printing technologies since the objects produced via 3D methods by using thermoplastic materials can be recycled and reformed easly. In order to use a thermoplastic material in the 3D technologies, the thermplastic polymers are spun into fiber structures and then 3D objects are produced from these fibers. In this regard, low density polyethylene (LDPE) and high density polyethylene (HDPE) were melt spun into fiber with various construction including neat, blend and bicomponent forms. Chemical, microstructural, thermal and mechanical properties of the produced fibers were investigated. 3D printable properties of the prepared fibers were observed by using them in the 3D printer. It was observed that bicomponent LDPE/HDPE fibers were the most suitable fiber to produced 3D sample in the lab scale 3D printer. 3D honeycomb structure was produced from this fiber and its compression strength property was investigated by comparing the same size of the PLA honeycomb structure. Compression strength test result of the honeycomb sample produced from LDPE/HDPE bicomponent fiber was close to compression strength test result of the PLA honeycomb sample. The results revelaled that LDPE/HDPE bicomponent fibers could be an alternative to PLA fiber in 3D printing technologies.

Chemotactic TEG3 Cells' Guiding Platforms Based on PLA Fibers Functionalized With the SDF-1α/CXCL12 Chemokine for Neural Regeneration Therapy.

(Following spinal cord injury, olfactory ensheathing cell (OEC) transplantation is a promising therapeutic approach in promoting functional improvement. Some studies report that the migratory properties of OECs are compromised by inhibitory molecules and potentiated by chemical concentration differences. Here we compare the attachment, morphology, and directionality of an OEC-derived cell line, TEG3 cells, seeded on functionalized nanoscale meshes of Poly(l/dl-lactic acid; PLA) nanofibers. The size of the nanofibers has a strong effect on TEG3 cell adhesion and migration, with the PLA nanofibers having a 950 nm diameter being the ones that show the best results. TEG3 cells are capable of adopting a bipolar morphology on 950 nm fiber surfaces, as well as a highly dynamic behavior in migratory terms. Finally, we observe that functionalized nanofibers, with a chemical concentration increment of SDF-1α/CXCL12, strongly enhance the migratory characteristics of TEG3 cells over inhibitory substrates.

A novel biodegradable porous graphitic carbon nitride/poly(lactic acid) fiber photocatalyst for efficient elimination of carbamazepine under solar irradiation

Developing efficient photocatalytic materials for the elimination of emerging contaminants is of great significance for wastewater treatment. However, photocatalysts in powder form usually suffer from the problems of easy agglomeration and difficult recycle in water. Herein, graphitic carbon nitride/polylactic acid (g-C3N4/PLA) fiber composites with highly hierarchical macro/mesoporous structure were constructed by a simple and efficient methods of centrifugal-electrostatic spinning and alkali treatment. The porous structure of fiber could provide abundant space to immobilize g-C3N4 nanosheets, avoiding the wrapping of g-C3N4 inside the fiber and creating more active sites for photocatalytic reaction. Importantly, the carbamazepine (CBZ) removal rate by porous g-C3N4/PLA fiber composites under solar irradiation was as high as 99% in 2 h. The reaction mechanisms and CBZ degradation pathways were identified. Superoxide radical (•O2−), singlet oxygen (1O2) and hole (h+) were regarded as dominant active species in porous g-C3N4/PLA photocatalytic system for photocatalytic degradation of CBZ. The porous fiber composites not only possessed superior photocatalytic activity, repeatability and stability, but also could be biodegraded in natural environment without secondary pollution. This work proposed a promising way for developing efficient, stable and environmental-friendly photocatalytic materials for the removal of CBZ and other emerging contaminants in wastewater.

Elaborating Mechanisms behind the Durability of Tough Polylactide Monofilaments under Elevated Temperature and Humidity Conditions

Melt-spun poly(l-lactic acid) (PLA) monofilaments with excellent toughness have been subjected to environmental weathering under varying temperatures in the range of 50–70 °C, that is, below and close to the glass transition temperature Tg, and at 20–95% relative humidity in order to follow the evolution of their mechanical performance. Environmentally triggered structural changes and the hydrolytic degradation of the monofilaments have been evaluated by analysis of their thermal and mechanical properties as well as their long-term relaxation behavior using a self-developed model. Despite structural changes, the fibers demonstrate a long-term preservation of the toughness under environmental conditions of physical aging. The mechanisms behind the observed durability of the PLA material are attributed to the relaxation of the confined amorphous phase presumably as a result of the local chain scission. Conditions when hydrolytic degradation leads to mechanical failure correspond to an absolute humidity of 90 g/m3 independent of the temperature of the aging. Presented results reveal a persistence of the mechanical performance of PLA fibers upon aging under moderate conditions, thus offering possible design strategies toward tough and durable PLA materials for sustainable technologies.

Design and analysis of 3D printed UAV wheel

Unmanned Aerial Vehicles of group 1 category are small in size with Maximum Gross Take-off Weight between 0 and 20 lbs and normal operating altitude as 1200 AGL (Above Ground Level). Light weighting in aerial vehicles is one of the major concerns and is mostly favoured by the change in materials. Tyres used for UAVs are extensively made up of rubber and are quite heavy in weight thus rising a concern. These rubber tyres add to the dead weight during the flight and also adds to the drag. For this study, lightweight 3D – printed wheels for better performance and lesser drag during the flight are designed and analysed for the group I UAV vehicles. The target is to reduce the weight by 50%, to achieve this, a rigorous analysis was performed for choosing the best possible configuration using various 3D – printing materials like ABS, PLA, Nylon and Carbon fibre mix. Additive manufacturing commonly known as 3D – printing favours the production of high strength light weighing parts. It also offers a broader range of design selection and favours iterative design approach and thus was opted as the method of production. The iterative design approach was followed to obtain the best results. Wheels with 4, 5, and 6 spokes were considered for the study. The wheel designs were modelled in Solidworks and analysis was conducted in Ansys using Finite Element Analysis to study the static and dynamic strength of the wheel in the radial direction, ignoring the bending and torsion of wheels during landing. Furthermore, the Charpy impact test was conducted on the specimen to study the crack propagation on impact.

Poly(lactic acid) fibers, yarns and fabrics: Manufacturing, properties and applications

Poly(lactic acid) (PLA) fiber was developed more than a decade ago. It has been regarded as the most promising sustainable and biodegradable fiber to replace conventional polyethylene terephthalate (PET) polyester fiber in textile products. This paper reviews recent developments in PLA polymerization, PLA filament and fiber spinning, staple yarn spinning, fabric production, dyeing and finishing and aftercare procedures. The properties of PLA fiber are broadly similar to those of PET fiber; however, the properties of PLA fiber that differ, including thermal degradation and low hydrolytic resistance to strong alkaline, significantly affect the method selection and parameter setting of production and processing of PLA fibers and fabrics. PLA filaments are mainly produced by two-step melt spinning to get fibers with stable quality, but degradation at high temperature is still a problem. PLA staple yarns are normally spun using ring spinning. Currently existing knitting or weaving techniques can be used to produce PLA fabrics. PLA fabrics can be dyed with disperse dyes at 110°C, but their color fastness and shades are different from PET fabrics when using the same dyes. The scouring and dyeing of PLA/cotton blended fabrics and the reductive clearing after dyeing remain to be improved. As a new fiber, the entry of PLA fiber into the textile market faces difficult challenges as well as great opportunities in the future.

In-situ microfibrillated Poly(ε-caprolactone)/ Poly(lactic acid) composites with enhanced rheological properties, crystallization kinetics and foaming ability

The present study aims at investigation on the morphology, rheology, isothermal crystallization and foaming behavior of the fibrillated PCL/PLA composites. The samples containing 5, 10 and 20 wt% PLA were melt-blended with PCL using a twin-screw extruder, following hot-stretching. The SEM morphology results revealed that the samples before stretching demonstrated spherical PLA domains; however, after stretching the spherical particles transformed to fibrillar structures and developed a 3D-network of entangled PLA fibers. Melt rheological properties of the samples before stretching suggested that the viscosity and storage modulus of the composites were increased with increasing the amount of PLA particles. This effect became more noticeable when the PLA domains were fibrillar. Moreover, rheological results unveiled that the fibrillated PCL/PLA composites showed a solid-like behavior which was evidenced with a plateau of storage modulus at low frequency region. Isothermal crystallization kinetics of the composites indicated that the PLA nanofibrils acting as heterogeneous nucleation, remarkably accelerated the crystallization at various crystallization temperature. Moreover, under high PLA nanofirbrils, the interaction between a large amout of induced PCL crystal nuclei and increased viscosity hinder motion of PCL molecules, which resulted in a higher isothermal crystallization activation energy. A close examination of batch foaming data suggested that the fibrillated samples induced further open-cell foams in comparison with that of the pure PCL and undrawn PCL/PLA samples.

Physical Properties, Chemical Analysis, and Evaluation of Antimicrobial Response of New Polylactide/Alginate/Copper Composite Materials.

In recent years, due to an expansion of antibiotic-resistant microorganisms, there has been growing interest in biodegradable and antibacterial polymers that can be used in selected biomedical applications. The present work describes the synthesis of antimicrobial polylactide-copper alginate (PLA–ALG–Cu2+) composite fibers and their characterization. The composites were prepared by immersing PLA fibers in aqueous solution of sodium alginate, followed by ionic cross-linking of alginate chains within the polylactide fibers with Cu(II) ions to yield PLA–ALG–Cu2+ composite fibers. The composites, so prepared, were characterized by scanning electron microscopy (SEM), UV/VIS transmittance and attenuated total reflection Fourier-transform infrared spectroscopy ATR-FTIR, and by determination of their specific surface area (SSA), total/average pore volumes (through application of the 5-point Brunauer–Emmett–Teller method (BET)), and ability to block UV radiation (determination of the ultraviolet protection factor (UPF) of samples). The composites were also subjected to in vitro antimicrobial activity evaluation tests against colonies of Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria and antifungal susceptibility tests against Aspergillus niger and Chaetomium globosum fungal mold species. All the results obtained in this work showed that the obtained composites were promising materials to be used as an antimicrobial wound dressing.

Biodegradation evaluation of poly (lactic acid) for stent application: Role of mechanical tension and temperature

AbstractIn this study, an experimental investigation is conducted on mechanical characteristics of poly(lactic acid) (PLA), before, and during degradation for stent application. A bioreactor is designed and fabricated to mimic in‐vivo environment of the body for studying degradation behavior of PLA fibers manufactured by melt spinning method. Beside PLA fibers, the degradation of PLA braided stents is investigated as control samples. To measure stress–strain and stress relaxation properties of PLA fibers, tensile, and relaxation tests are conducted. The decreasing trend of Young's modulus, variations in residual stress value after relaxation and pattern of stress relaxation are found during degradation. The influence of effective parameters, that is, temperature and stress, on PLA degradation is also studied. Moreover, the PLA degradation is analyzed by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA) and microscopic images. GPC results indicate the molecular weight decreases from 196,000 to 80,000 due to degradation while DSC analysis confirmed that the degradation promote an increase in PLA degree of crystallinity (from 43.3% to 59.8%). In addition, TGA results show that the PLA thermal stability decreases during degradation. This study provides useful information on PLA properties during degradation to assess the material in context of degradable stents.

The efficacy of nanoclay loading in the medium velocity impact resistance of kenaf/PLA biocomposites

This work focused on investigating the efficacy of clay nanoparticles loading in the medium velocity impact resistance of kenaf/polylactic acid (PLA) biocomposites. Kenaf/PLA biocomposites with different nanoclay loadings of 0, 3, 5 and 7% by weight were fabricated and their medium velocity impact resistance tested on a gas gun. Results indicate that the addition of nanoclay in the biocomposites improved the medium velocity impact resistance of the biocomposites, specifically the perforation threshold limit, energy absorbed, crack and damage resistance. Improvements on these properties were thought to be due to enhancements brought about by the nanoclays on interfacial bonding and microstructural properties of the biocomposites revealed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The nanoclays reduced the micro-voids thereby improving bonding between PLA and kenaf fibres. SEM–EDX analysis detected silicon and aluminium elements which were from the nanoclays and the elemental maps showed that all the elements were uniformly distributed in all cases with good dispersion of the nanoclays. However, incidences of nanoclay agglomeration were observed at 7 wt% nanoclay content which had adverse effects on the biocomposites properties. Optimum results were achieved with 5 wt% nanoclay content, beyond which a reduction in the medium velocity impact resistance was observed. The perforation threshold, energy absorption capacity, resistance to damage and prevention of crack propagation increased by 41.9, 109, 26.5 and 28.9%, respectively, at the 5 wt% nanoclay content level. The study shows that the addition of nanoclay improves the impact properties of kenaf/PLA biocomposites within the medium velocity range. The novel nanoclay impregnated biocomposite material developed is suitable for applications where good impact properties are required.

Antimicrobial food packaging system based on ethyl lauroyl arginate-loaded core/shell electrospun structures by using hydrophilic and hydrophobic polymers

Antimicrobial compounds can be encapsulated into core/shell structures through coaxial electrospinning in order to develop novel active food packaging materials. In this work, poly (vinyl alcohol)-(ethyl lauroyl arginate)/poly (lactic acid) core/shell fibers, (PVOH-LAE/PLA)f, were developed with the purpose to study the influence of combining a hydrophilic and a hydrophobic polymer on LAE release. LAE release studies were carried out in an aqueous and fatty food simulant, and data were analyzed through a phenomenological mass transfer model. Flat-ribbon fibers with a core/shell structure were observed by TEM. PLA crystallinity degree of coaxial fibers did not present significant differences with uniaxial PLA fibers, although thermal stability and the glass transition temperature decreased. The maximum concentrations of LAE released from (PVOH-LAE/PLA)f fibers to both simulants reached the MIC values of LAE against Listeria innocua, evidencing a higher affinity of LAE towards fatty simulant and a fast diffusion from fibers in the aqueous simulant.

Polypyrrole-chitosan hydrogel reinforced with collagen-grafted PLA sub-micron fibers as an electrically responsive scaffold

Hydrogel/fiber composites (HFC) improved by bio-related modifications have emerged as compelling scaffolds for regenerative medicine. In this study, by adding collagen-grafted poly-L-lactic acid fibers and genipin as a chemical cross-linker to synthesize polypyrrole-chitosan precursor, conductive HFC scaffolds were prepared. Techniques, including microscopy, mechanical analysis, conductivity measurement, and cell culture studies, are used to assess fibers and HFC scaffolds' structural, electrical, and functional performances. The scaffold is biocompatible according to the results of MTT assay and attachment of PC-12 cells. In conclusion, polypyrrole-chitosan hydrogel reinforced by collagen-grafted PLA fibers is suggested to be a potential scaffold for electrically responsive tissue applications.

Electrospinning-electrospraying of poly(acid lactic) solutions in binary chloroform/formic acid and chloroform/acetic acid mixtures

Poly(acid lactic) (PLA) is a synthetic, cytocompatible, and biodegradable biopolymer. It provides materials for drug delivery, food packing, and tissue engineering applications. Here, we provide the electrospinning of PLA (Mw = 26,000 Da) solutions (20–35% wt/vol) in binary chloroform/formic acid mixtures. The formic acid content between 20 and 40 vol% support smooth PLA fibers (average size between 231 and 637 nm). The electrospraying of PLA solutions (10–25% wt/vol) in chloroform creates smooth microparticles (average size between 1.0 and 11.4 μm). Contents of acetic acid higher than 10 vol% in binary chloroform/acetic acid mixtures prevent the formation of microparticles. Viscosity and conductivity measurements were carried out with the polymer solutions and the binary solvent mixtures, respectively. By modulating the polymer concentration and solvent system, we control the process, achieving electrospinning or electrospraying. Scanning electron microscopy and infrared spectroscopy characterized the PLA materials. This study reports accessible approaches to support micro- and nano-sized PLA materials.

Axonal extension from dorsal root ganglia on fibrillar and highly aligned poly(lactic acid)-polypyrrole substrates obtained by two different techniques: Electrospun nanofibres and extruded microfibres

The biological behaviour of Schwann cells (SCs) and dorsal root ganglia (DRG) on fibrillar, highly aligned and electroconductive substrates obtained by two different techniques is studied. Mats formed by nanometer-sized fibres of poly(lactic acid) (PLA) are obtained by the electrospinning technique, while bundles formed by micrometer-sized extruded PLA fibres are obtained by grouping microfibres together. Both types of substrates are coated with the electrically conductive polymer polypyrrole (PPy) and their morphological, physical and electrical characterization is carried out. SCs on micrometer-sized substrates show a higher motility and cell-cell interaction, while a higher cell-material interaction with a lower cell motility is observed for nanometer-sized substrates. This higher motility and cell-cell interaction of SCs on the micrometer-sized substrates entails a higher axonal growth from DRG, since the migration of SCs from the DRG body is accelerated and, therefore, the SCs tapestry needed for the axonal growth is formed earlier on the substrate. A higher length and area of the axons is observed for these micrometer-sized substrates, as well as a higher level of axonal sprouting when compared with the nanometer-sized ones. These substrates offer the possibility of being electrically stimulated in different tissue engineering applications of the nervous system.

Noninvasive characterization (EPR, μCT, NMR) of 3D PLA electrospun fiber sponges for controlled drug delivery

Highly porous 3D-scaffolds, made from cut, electrospun PLA fibers, are relatively new and promising systems for controlled drug-delivery applications. Because knowledge concerning fundamental processes of drug delivery from those scaffolds is limited, we noninvasively characterized drug-loading and drug-release mechanisms of these polymer-fiber sponges (PFS). We screened simplified PFS-implantation scenarios with EPR and μCT to quantify and 3D-visualize the absorption of model-biofluids and an oil, a possible drug-loading liquid. Saturation of PFS (6 × 8 mm, h x d) is governed by the high hydrophobicity of the material and air-entrapment. It required up to 45 weeks for phosphate-buffered saline and 11 weeks for a more physiological, surface-active protein-solution, indicating the slow fluid-uptake of PFS as an effective mechanism to substantially prolong the release of a drug incorporated within the scaffold. Medium-chain triglycerides, as a good wetting liquid, saturated PFS within seconds, suggesting PFS potential to serve as carrier-vessels for immobilizing hydrophobic drug-solutions to define a liquid's 3D-interface. Oil-retention under mechanical stress was therefore investigated. 1H NMR permitted insights into PFS-oil interaction, confirming surface-relaxation and restricted diffusion; both did not influence drug release from oil-loaded PFS. Results facilitate better understanding of PFS and their potential use in drug delivery.

Development of Dyeing Process for Sulphatoethylsulphone Reactive-Disperse Dye on Natural and Synthetic Fibers

Sulphatoethylsulphone reactive-disperse dye was synthesized via diazotization reaction of aminophenyl-4-(β-sulphatoethylsulphone) followed by coupling reaction of the diazonium salt with phenol as a coupling agent. The synthesized dye was well dyeable on both natural and synthetic fibers with providing orange shade on cotton, silk and nylon, while the dyed PLA and PET fibers appeared in yellow shade. The dyeing conditions for cotton and silk could be conducted using 60 g/l Na2SO4 and 20 g/l Na2CO3 at 60°C for 90 minutes whereas dyeing on PLA and PET fibers was optimally done at 110°C for 30 and 45 minutes for PLA and PET, respectively. In case of nylon, it could be dyed at 100°C for 15 minutes. The synthesized reactive-disperse dye could well dye on these 5 fibers with excellent color fastness to washing.

Surface-porous and hollow poly(lactic acid) (SPH-PLA) and surface-porous and lotus-root-like PLA (SPL-PLA) nanofibres: preparation, quantitative analysis, and modelling

In this study, PLA nanofibres with unique microstructures were prepared by coaxial electrospinning. The cross-section of the prepared PLA nanofibres exhibited either a surface-porous hollow structure (SPH-PLA) or a surface-porous lotus-root-like structure (SPL-PLA). The morphology, hollow proportion, and porosity of the fibres under different electrospinning parameter conditions were analysed quantitatively; further, three-dimensional (3D) models of the PLA nanofibres were established under parameter conditions that provided the highest hollow proportion. The results of the analysis revealed that the diameter fluctuated only slightly with the process parameters. Additionally, variations in the different electrospinning parameters caused only a slight change in the surface porosity (i.e. only 31% ± 4%) of the PLA fibres. The total porosity of the section (termed the pore porosity), porosity of the hollow section (termed the hollow porosity), R value (R = hollow porosity/pore porosity), and number of small pores of the SPH-PLA nanofibres did not change significantly with the receiving distance; the change observed was approximately only by 38% ± 2%, 28% ± 2%, 75% ± 5%, and 11 ± 1, respectively. Further, the cross-sectional porosity of the SPL-PLA nanofibres also did not change significantly with the receiving distance, only by approximately 24% ± 2%. The hollow proportion was the highest (76.32% ± 8.34%) at a core/shell flow rate ratio of 0.3:0.9 (mL/h), spinning voltage of 19 kV, and receiving distance of 6 cm. Therefore, 3D models of the SPH-PLA and SPL-PLA nanofibres were established under these electrospinning parameters.

Design and verification of enhanced CFRTPCs fabrication technique using fused deposition modeling

Research shows that mechanical properties of parts produced using fused deposition modeling (FDM) are inferior when compared to parts produced using conventional techniques such as injection molding. Efforts have been made in recent years to improve mechanical properties by reinforcing the parts with high strength fibers. This has been achieved by either modifying FDM setups to extrude fibers with thermoplastics and fabricate continuous fiber reinforced thermoplastic composites (CFRTPCs) or employing manual techniques subsequent to part production. Existing CFRTPCs fabrication procedures have limitations of fiber exposure to environment, no direct control method for volume fraction, and poor surface finish. This research work is focused on improving the process of producing CFRTPCs by addressing these limitations using a dual extruder FDM setup. The process developed was tested for its feasibility using Kevlar fiber as reinforcement for commercially available ABS, PLA, PLA-C, and PLA-Cu thermoplastic fibers. Taguchi L16 orthogonal array was used to design experiments, while tensile and flexural testing was performed to determine mechanical properties achieved. Tensile strength was improved up to 3 times the baseline value of thermoplastics, while flexural strength was improved up to 1.6 times. This technique can further the goal of developing CFRTPCs, on industrial level, using FDM with better control over volume fraction and fiber layup.