Mechanical Properties Of Fibers Research Articles

Branchwood Properties of Two Tilia Species Collected from Natural Secondary Forests in Northeastern China

Tilia amurensis Rupr. and Tilia mandshurica Rupr. and Maxim. are two essential commercial species, though there is surprisingly little concern about whether their branches can be used in the current situation of a wood shortage in China. In this study, tissue proportions and fiber morphology, physical and mechanical properties, and chemical composition of the branchwood were studied and compared with stemwood to evaluate the potential for papermaking. The branchwood and stemwood showed similar cell arrangement but different tissue proportions and fiber morphology. The branchwood had more than 40% fiber proportion, 90%–97% below 0.9 mm in length, 75%–90% less than 33 in slenderness ratio, and 80% less than 1 in Runkel ratio. The branchwood was as light and soft as stemwood with a density of 0.32–0.36 g/cm3 and a compressive strength of about 30 MPa. The branchwood had 6% water extractives, 66% holocellulose, and 22% lignin for T. amurensis, 58% holocellulose and 30% lignin for T. mandshurica. The results suggest the branchwood is favorable for mechanical chipping, has the potential to obtain high pulp yield and its fibers can be mixed with wide, long and thick fibers from other tree species to produce specific paper products. In contrast, T. mandshurica branchwood may not be suitable for chemical pulping.

Fabrication of drug-eluting polycaprolactone and chitosan blend microfibers for topical drug delivery applications

Chronic and non-healing wounds show delayed and incomplete healing process, which expose the patients to a high risk of infection. These types of wounds require frequent change of dressing, which is a burden on the patients. In addition, ideal dressing needs to meet the requirements in minimizing microbial infiltration and growth while balancing moisture and exchanging oxygen with outside environment. To overcome the challenge in frequent change of dressing and meet the design requirements, current researches have focused on the development of electrospun fibers with incorporation of small molecule drugs for sustained release purpose. In this study, electrospinning was performed to fabricate blend fibers consisting of 15 wt% of polycaprolactone (PCL) and 4 wt% of chitosan (CS) at various blend ratios with the incorporation of a model small molecule drug, acetylsalicylic acid (ASA). Results showed that fibers became more hydrophilic when increasing CS concentration from 0% to 60% in PCL/CS blank fibers. Increasing CS concentration decreased fiber diameter resulting in the decrease of fiber mechanical properties. Furthermore, the addition of 10% w/w ASA also made the fibers more hydrophilic and further decreased the fiber diameter. There were no linear relationships between CS concentrations and fiber mechanical properties in the drug-loaded samples, which indicated some level of drug-polymer interactions. Fiber mechanical properties and drug release rates were two major aspects indicative of strong and/or weak drug-polymer interactions. In vitro drug release in PBS buffer solution showed a burst profile of ASA (30%) up to 2 h followed by a zero-order release rate up to 2 days.

Activated Carbon-Enriched Electrospun-Produced Scaffolds for Drug Delivery/Release in Biological Systems.

To vectorize drug delivery from electrospun-produced scaffolds, we introduce a thin outer drug retention layer produced by electrospinning from activated carbon nanoparticles (ACNs)-enriched polycaprolacton (PCL) suspension. Homogeneous or coaxial fibers filled with ACNs were produced by electrospinning from different PCL-based suspensions. Stable ACN suspensions were selected by sorting through solvents, stabilizers and auxiliary components. The ACN-enriched scaffolds produced were characterized for fiber diameter, porosity, pore size and mechanical properties. The scaffold structure was analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that ACNs were mainly coated with a polymer layer for both homogeneous and coaxial fibers. Drug binding and release from the scaffolds were tested using tritium-labeled sirolimus. We showed that the kinetics of sirolimus binding/release by ACN-enriched scaffolds was determined by the fiber composition and differed from that obtained with a free ACN. ACN-enriched scaffolds with coaxial and homogeneous fibers had a biocompatibility close to scaffold-free AC, as was shown by the cultivation of human gingival fibroblasts and umbilical vein cells on scaffolds. The data obtained demonstrated that ACN-enriched scaffolds had good physico-chemical properties and biocompatibility and, thus, could be used as a retaining layer for vectored drug delivery.

FN (Fibronectin)-Integrin α5 Signaling Promotes Thoracic Aortic Aneurysm in a Mouse Model of Marfan Syndrome.

Marfan syndrome, caused by mutations in the gene for fibrillin-1, leads to thoracic aortic aneurysms (TAAs). Phenotypic modulation of vascular smooth muscle cells (SMCs) and ECM (extracellular matrix) remodeling are characteristic of both nonsyndromic and Marfan aneurysms. The ECM protein FN (fibronectin) is elevated in the tunica media of TAAs and amplifies inflammatory signaling in endothelial and SMCs through its main receptor, integrin α5β1. We investigated the role of integrin α5-specific signals in Marfan mice in which the cytoplasmic domain of integrin α5 was replaced with that of integrin α2 (denoted α5/2 chimera). We crossed α5/2 chimeric mice with Fbn1mgR/mgR mice (mgR model of Marfan syndrome) to evaluate the survival rate and pathogenesis of TAAs among wild-type, α5/2, mgR, and α5/2 mgR mice. Further biochemical and microscopic analysis of porcine and mouse aortic SMCs investigated molecular mechanisms by which FN affects SMCs and subsequent development of TAAs. FN was elevated in the thoracic aortas from Marfan patients, in nonsyndromic aneurysms, and in mgR mice. The α5/2 mutation greatly prolonged survival of Marfan mice, with improved elastic fiber integrity, mechanical properties, SMC density, and SMC contractile gene expression. Furthermore, plating of wild-type SMCs on FN decreased contractile gene expression and activated inflammatory pathways whereas α5/2 SMCs were resistant. These effects correlated with increased NF-kB activation in cultured SMCs and mgR aortas, which was alleviated by the α5/2 mutation or NF-kB inhibition. FN-integrin α5 signaling is a significant driver of TAA in the mgR mouse model. This pathway thus warrants further investigation as a therapeutic target.

Incorporation of strontium-containing bioactive particles into PEOT/PBT electrospun scaffolds for bone tissue regeneration

The combination of biomaterials and bioactive particles has shown to be a successful strategy to fabricate electrospun scaffolds for bone tissue engineering. Among the range of bioactive particles, hydroxyapatite and mesoporous bioactive glasses (MBGs) have been widely used for their osteoconductive and osteoinductive properties. Yet, the comparison between the chemical and mechanical characteristics as well as the biological performances of these particle-containing scaffolds have been characterized to a limited extent. In this work, we fabricated PEOT/PBT-based composite scaffolds incorporating either nanohydroxyapatite (nHA), strontium-containing nanohydroxyapatite (nHA_Sr) or MBGs doped with strontium ions up to 15 wt./vol% and 12,5 wt./vol% for nHA and MBG, respectively. The composite scaffolds presented a homogeneous particle distribution. Morphological, chemical and mechanical analysis revealed that the introduction of particles into the electrospun meshes caused a decrease in the fiber diameter and mechanical properties, yet maintaining the hydrophilic nature of the scaffolds. The Sr2+ release profile differed according to the considered system, observing a 35-day slowly decreasing release from strontium-containing nHA scaffolds, whereas MBG-based scaffolds showed a strong burst release in the first week. In vitro, culture of human bone marrow-derived mesenchymal stromal cells (hMSCs) on composite scaffolds demonstrated excellent cell adhesion and proliferation. In maintenance and osteogenic media, all composite scaffolds showed high mineralization as well as expression of Col I and OCN compared to PEOT/PBT scaffolds, suggesting their ability to boost bone formation even without osteogenic factors. The presence of strontium led to an increase in collagen secretion and matrix mineralization in osteogenic medium, while gene expression analysis showed that hMSCs cultured on nHA-based scaffolds had a higher expression of OCN, ALP and RUNX2 compared to cells cultured on nHA_Sr scaffolds in osteogenic medium. Yet, cells cultured on MBGs-based scaffolds showed a higher gene expression of COL1, ALP, RUNX2 and BMP2 in osteogenic medium compared to nHA-based scaffolds, which is hypothesized to lead to high osteoinductivity in long term cultures.

Investigation of recycling effects on the mechanical properties of short carbon and glass fiber reinforced polyetherimide composites

AbstractConsidering the increasing composite waste accumulation, this work explores the feasibility of replacing virginal carbon fibers (VCFs) and virginal glass fibers (VGFs) with recycled fibers for injection molded polyetherimide (PEI) composites. Extensive characterizations were conducted to reveal effects of sulfuric acid recycling process on mechanical properties of fibers and their composites. It was shown that strength retention rates of recycled carbon fibers (RCFs) and recycled glass fibers (RGFs) were 81.6% and 55.7%. The reinforcing factor of RCFs increased from 0.120 of VCFs to 0.147 due to the enhanced interfacial bonding while the reinforcing factor of RGFs decreased from 0.080 of VGFs to 0.065 owing to the glass fiber strength reduction. As a result, the composite tensile strength (152.8 MPa) of RCF/PEI was comparable to that (155.3 MPa) of VCF/ PEI and RGF/PEI tensile strength (102.5 MPa) was lower than that (112.3 MPa) of VGF/PEI. Moreover, the tensile modulus of RCF/PEI and RGF/PEI were also approximatively comparable to those of VCF/PEI and VGF/PEI since recycling process showed a slight effect on fiber modulus. Although there exists an impact of recycling on fiber mechanical properties, the introduction of recycled fibers (especially RCFs) by injection molding process can promisingly enhance PEI composites.

Research on fiber laser welding formation, microstructure, and mechanical properties of 7.5 mm 304 stainless steel

304 austenitic stainless steel with a thickness of 7.5 mm was welded by high-power fiber laser welding. The effects of main welding parameters, including laser power, welding speed, and defocusing amount, on weld formation were studied in detail. The welding parameters were optimized according to the weld formation. On this basis, the microstructure and mechanical properties of the welded joints were further analyzed. The results showed that depression and hump defects easily occurred once the joints were penetrated. The defects could be effectively avoided when two specific parameters were adopted: namely, high-power laser welding with high speed at the focal position or low speed at the far defocusing position; both could reduce the impact of metal vapor in the keyhole on the molten pool, and meet the requirements of penetration and stability to obtain well-formed welds. High-speed welding obtained nail-shaped weld, and Peanut-shaped weld was obtained by low-speed welding. The microstructure of the welds was mainly composed of massive austenite and a small amount of ferrite, indicating that the solidification abided by the F-A mode according to the pseudo-binary phase diagram. Due to the smaller grain size, the hardness of the Nail-shaped weld (238.8HV0.3) was higher than that of the Peanut-shaped weld (223.4HV0.3). The tensile strength of the Nail-shaped weld joint and Peanut-shaped weld joint were 677 MPa and 689 MPa, which reached more than 95% of the base metal.

Recent Advances in Centrifugal Spinning and Their Applications in Tissue Engineering.

Over the last decade, researchers have investigated the potential of nano and microfiber scaffolds to promote wound healing, tissue regeneration, and skin protection. The centrifugal spinning technique is favored over others due to its relatively straightforward mechanism for producing large quantities of fiber. Many polymeric materials have yet to be investigated in search of those with multifunctional properties that would make them attractive in tissue applications. This literature presents the fundamental process of fiber generation, and the effects of fabrication parameters (machine, solution) on the morphologies such as fiber diameter, distribution, alignment, porous features, and mechanical properties. Additionally, a brief discussion is presented on the underlying physics of beaded morphology and continuous fiber formation. Consequently, the study provides an overview of the current advancements in centrifugally spun polymeric fiber-based materials and their morphological features, performance, and characteristics for tissue engineering applications.

Biomechanical Response of Four Roussouly's Sagittal Alignment Lumbar to Degeneration of Different Parts of Intervertebral Disc: Finite Element Model Analysis

BackgroundSpinal degeneration with age is commonly accompanied by excessive kyphosis and low-back pain, however, little is known about the connection between lumbar sagittal morphology and its degenerative biomechanics. This study investigates the biomechanical response of four Roussouly's sagittal alignment lumbar to degeneration of various parts of the intervertebral disc (IVD) based on threedimensional finite element (FE) models. MethodsUsing Roussouly's type parametric FE models, material properties of the degenerate nucleus populous (NP), annulus fibrosis matrix (AFM), and collagen fibers were assumed to be half of the intact IVD. A follower preload and vertical force were applied to simulate physical standing posture. Resultsthe reduced strength of the NP and AFM led to the increase of lumbar anteflexion, while the fiber mechanical properties have little effect on it. When facing IVD degeneration, Type 1 lumbar showed increased intradiscal pressures (IDPs) and fiber stress at the L1-2 and L4-S1 segments. Type 2 lumbar exhibited the highest lumbar anteflexion and pelvic rearward rotation, as well as increased IDPs among the models. Type 3 lumbar had the best biomechanical stability. Type 4 lumbar showed the higher AFM stress but the lower IDPs among the four types. ConclusionsIVD degeneration generated sagittal imbalance by increasing lumbar anteflexion movement (i.e., loss lordosis) and pelvic rearback rotation. The biomechanical response of the four Roussouly's lumbar types differed in intervertebral rotation and stress distribution.

Impact of wet-drying Treatment of Raffia and Okra Fibres on Their Morphological, Physicochemical and Mechanical Properties

ABSTRACT Hornification is an irreversible effect that occurs on lignocellulosic fibers when they are subjected to drying and re-wetting cycles. This study aimed to evaluate okra and raffia fibers morphological, physico-chemical, and mechanical properties. The fibers were subjected to four and six wet-dry treatment cycles to assess the effect of the number of cycles on the performance of each fiber. The results show that four wet-dry cycles show an increase in density from 1.40 g/cm3 to 1.78 g/cm3 and from 1.34 g/cm3 to 1.58 g/cm3 for okra and raffia fibers, respectively. Furthermore, a decrease in fiber lumen is observed, resulting in a reduction in water absorption capacity of up to 18.3% for raffia fiber and 56.3% for okra after four hornification cycles. Statistical analysis reveals a significant improvement in the elastic modulus of raffia fiber up to 37% after treatment, while no significant improvement is observed in the elastic modulus and tensile strength of okra fiber. This is attributed to the strengthening of intracellulosic bonds, which resulted in the creation of more available -OH sites on the fibers. The physico-chemical and mechanical changes in fiber properties resulting from wet-dry processing have demonstrated their suitability to replace synthetic fibers in composites.

Removal of GAGs Regulates Mechanical Properties, Collagen Fiber Formation, and Alignment in Tissue Engineered Meniscus.

The complex fibrillar architecture of native meniscus is essential for proper function and difficult to recapitulate in vitro. In the native meniscus, proteoglycan content is low during the development of collagen fibers and progressively increases with aging. In vitro, fibrochondrocytes produce glycosaminoglycans (GAGs) early in culture, in contrast to native tissue, where they are deposited after collagen fibers have formed. This difference in the timing of GAG production hinders the formation of a mature fiber network in such in vitro models. In this study, we removed GAGs from collagen gel-based tissue engineered constructs using chondroitinase ABC (cABC) and evaluated the effect on the formation and alignment of collagen fibers and the subsequent effect on tensile and compressive mechanical properties. Removal of GAGs during maturation of in vitro constructs improved collagen fiber alignment in tissue engineered meniscus constructs. Additionally, removal of GAGs during maturation improved fiber alignment without compromising compressive strength, and this removal improved not only fiber alignment and formation but also tensile properties. The increased fiber organization in cABC-treated groups also appeared to influence the size, shape, and location of defects in these constructs, suggesting that treatment may prevent the propagation of large defects under loading. This data gives another method of modulating the ECM for improved collagen fiber formation and mechanical properties in tissue engineered constructs.

Carbon fiber surface nano-modification and enhanced mechanical properties of fiber reinforced cementitious composites

It has been widely recognized that fiber–matrix interface has great significance on the performance of fiber-reinforced cementitious composites. In this research, an effective fiber modification method is proposed and its enhanced mechanical properties are observed. Through the condensation and polymerization of the tetraethyl orthosilicate under alkaline conditions, a thin SiO2 layer was formed on carbon fiber surface, which can react with Ca(OH)2 thus form calcium silicate hydrate to condense the fiber–matrix interface. In this paper, nano-SiO2 modified carbon fibers are produced and the mechanical properties of modified carbon fiber reinforced cementitious composites are investigated. Modified material exhibited 24.7% enhancement in flexural strength and up to 25.1% enhancement in tensile strength with the fiber volume fraction of 0.5%. Better post-crack behavior and toughness properties were also estimated, which were attributed to nano-modification strengthening the ITZ through the reaction of surface nano-SiO2 with Ca(OH)2 resulting in much more amount of CSH gel and a denser microstructure of fiber–matrix interface. The microstructure of denser interface and porosity can be found through SEM and BSEM analysis. The porosity on the observation surface of interface transition zone of unmodified fiber and modified fiber was 4.03% and 2.43%, respectively. The change of chemical elements in the interface transition zone was analyzed by line scanning, and the Ca/Si of the modified carbon fiber was significantly lower than that of the unmodified carbon fiber.

Tyrosine's Unique Role in the Hierarchical Assembly of Recombinant Spider Silk Proteins: From Spinning Dope to Fibers.

Producing recombinant spider silk fibers that exhibit mechanical properties approaching native spider silk is highly dependent on the constitution of the spinning dope. Previously published work has shown that recombinant spider silk fibers spun from dopes with phosphate-induced pre-assembly (biomimetic dopes) display a toughness approaching native spider silks far exceeding the mechanical properties of fibers spun from dopes without pre-assembly (classical dopes). Dynamic light scattering experiments comparing the two dopes reveal that biomimetic dope displays a systematic increase in assembly size over time, while light microscopy indicates liquid-liquid-phase separation (LLPS) as evidenced by the formation of micron-scale liquid droplets. Solution nuclear magnetic resonance (NMR) shows that the structural state in classical and biomimetic dopes displays a general random coil conformation in both cases; however, some subtle but distinct differences are observed, including a more ordered state for the biomimetic dope and small chemical shift perturbations indicating differences in hydrogen bonding of the protein in the different dopes with notable changes occurring for Tyr residues. Solid-state NMR demonstrates that the final wet-spun fibers from the two dopes display no structural differences of the poly(Ala) stretches, but biomimetic fibers display a significant difference in Tyr ring packing in non-β-sheet, disordered helical domains that can be traced back to differences in dope preparations. It is concluded that phosphate pre-orders the recombinant silk protein in biomimetic dopes resulting in LLPS and fibers that exhibit vastly improved toughness that could be due to aromatic ring packing differences in non-β-sheet domains that contain Tyr.

Effect of Fiber Modification on Pineapple Leaf Fiber's Mechanical Properties and Interfacial Adhesion

Effect of Fiber Modification on Pineapple Leaf Fiber's Mechanical Properties and Interfacial Adhesion

The evolution of carbon fiber elements and their effects on fiber mechanical properties from molecular dynamics

Carbon fibers are ideal light-weight materials for aerospace applications due to their properties such as high strength, high modulus. As a result, there are significant efforts aimed at studying the theory of fiber structure and fabrication methods. The mechanical performance of carbon fibers can be controlled by the interaction of many complex factors, one of them being the element characteristic. Here, we use the molecular dynamics simulations to predict the evolution of non-carbon elements during heating and their responses to mechanical behavior. Particularly, the possible structures of N, O and Si are comprehensively studied. It is observed that Si results in the formation of CNSi chains and OH residues, which hinders the improvement of the strength of the carbon fibers. The oxygen-containing groups of the terminal ester can increase the content of adjacent chain structures that preferentially participate in carbonization. The O groups of hydroxypyridine lead to significantly lower carbonization onset temperature of polyacrylonitrile (PAN) via the pathway for H2O elimination, while the reaction rate of the H2O molecules is relevant to the PAN chain length distribution and local density. Interestingly, in the case of oxygen-modified carbon fibers, the Young’s modulus is predominantly affected. The release temperature of N, ranked from lowest to highest, is given by the chain-end CN group > hydrogenated-CN > unhydrogenated-CN, and the “transfer hopping” effect of the N element on the activated carbon chains contributes to carbon rearrangement during carbonization. The modified carbon ring structure comprising of 1.0–3.0 wt% N element is beneficial factor for conferring high tensile strength and large elongation to the carbon fibers. Our results provide valuable insights for the preparation and screening of high-performance carbon fibers from an elemental perspective, which can pave the way for a systematic framework for optimizing their performance.

Evaluation of the density, mechanical, thermal and chemical properties of babassu fibers (Attalea speciosa.) for potential composite reinforcement

The properties of babassu (Attalea speciosa.) fiber was for the first time investigated for potential engineering application such as reinforcement for matrix composites. The diameter distribution of babassu fibers was analyzed and found to be associated with significant variation in fiber density and mechanical properties. Additionally, thermogravimetric and Fourier transform infrared spectrometry (FTIR) analyses were performed. The studied Weibull statistical method was used to analyze the acquired data. The surface morphology of the fibers was studied by scanning electron microscopy. From the diameter ranges, it was possible to confirm that the thinner fibers have higher values of density and mechanical properties, which was attributed to their lower presence of defects. The diameter range was found between of 0.18 and 0.47 mm, and the corresponding densities were 0.79 and 0.27 g/cm³ respectively. Furthermore, the maximum tensile strength found was 100.76 MPa with an elastic modulus of 6.33 GPa and an elongation of 2.98%. Thermogravimetric analyses revealed a three-step mass loss, the main one being the second where the fiber loses 69% of the mass at a temperature of 382 °C. The FTIR analysis showed a similarity with the bands generally found in the literature for natural lignocellulosic fibers.

Characterization of Electrospun Polysuccinimide-Dopamine Conjugates and Effect on Cell Viability and Uptake.

Biocompatible nanofibrous systems made by electrospinning have been studied widely for pharmaceutical applications since they have a high specific surface and the capability to make the entrapped drug molecule amorphous, which increases bioavailability. By covalently conjugating drugs onto polymers, the degradation of the drug as well as the fast clearance from the circulation can be avoided. Although covalent polymer-drug conjugates have a lot of advantages, there is a lack of research focusing on their nano-formulation by electrospinning. In this study, polysuccinimide (PSI) based electrospun fibrous meshes conjugated with dopamine (DA) are prepared. Fiber diameter, mechanical properties, dissolution kinetics and membrane permeability are thoroughly investigated, as these are crucial for drug delivery and implantation. Dopamine release kinetics prove the prolonged release that influenced the viability and morphology of periodontal ligament stem cells (PDLSCs) and SH-SY5Y cells. The presence of dopamine receptors on both cell types is also demonstrated and the uptake of the conjugates is measured. According to flow cytometry analysis, the conjugates are internalized by both cell types, which is influenced by the chemical structure and physical properties. In conclusion, electrospinning of PSI-DA conjugates alters release kinetics, meanwhile, conjugated dopamine can play a key role in cellular uptake.

Effect of nanosilica on fiber pullout behavior and mechanical properties of strain hardening ultra-high performance concrete

The bond properties between the fiber and matrix are a critical factor that affects the tensile properties and toughness of fiber-reinforced cementitious composites. This research aims to provide an effective method to improve the tensile properties of ultra-high performance concrete (UHPC) with strain hardening characteristics. The compressive, flexural, and tensile behavior was measured on UHPC with two geometric configurations of steel fibers and four nanosilica (nano-SiO2) mass fractions (0/1/3/5 wt% substitution rate of cement mass). The pull-out load-slip responses of steel fibers were also captured. In particular, determined the effect of fiber slip response on tensile properties of UHPC, then calculate elastic, strain hardening, and softening tensile parameters. Furthermore, the SEM, EDS, MIP, and XRD tests were used to reveal the enhancement mechanism of interfacial bonding performance and mechanical properties. The results show that the compressive and flexural strength peaks at 3 wt% of nanosilica, owing to nanosilica effectively ameliorating the pore structure and promoting the hydration process of the matrix. While the fiber pullout behavior and tensile properties show better performance at 5 wt% associated with increased hydration products attached to the fiber surface and more severe scratches after being pulled out. Notably, the addition of nanosilica endows strain hardening properties to UHPC containing straight fibers as well as increases the tensile toughness of UHPC containing hooked fibers due to the reinforcement of the matrix tunnel surrounding the steel fibers.

Relation between injection molding conditions, fiber length and mechanical properties for highly reinforced long fiber polypropylene

AbstractA complete study on the relation between the injection molding parameters and the resulting fiber length, orientation and mechanical properties is presented for highly reinforced long fiber thermoplastic (LFT) polypropylene (PP). It has been found that the longest fibers obtained are the ones processed with the lowest backpressure and the highest screw speed. The backpressure gains importance over screw speed when the amount of glass fiber reinforcement increases, contrary to what was found for less reinforced thermoplastics. The injection speed does not influence the fiber breakage phenomena, while it has great importance in fiber orientation and thus on the tensile strength, especially when the weight fiber average length is below 1000 μm. When this average is over 1000 μm, fibers begin to weave a mesh that thickens the core region and hinds its orientation, reducing the tensile strength but improving impact resistance.

The study of correlations among the process condition, structure and property for poly(l-lactide) fibers

This article focus on derive the process-structure-property relationship of Poly(l-lactide) (PLLA) fibers prepared by two-step melt spinning process. The spinning temperature, spinning rate, drawing temperature as well as draw ratio were studied to analyze the influence of process variables on the structure and properties of PLLA fibers. It suggests that the crystallinity, lamellar orientation structure and mechanical properties of fibers are dependent on the spinning conditions, including melt-spinning and hot-drawing process. An approximate linear correlation resulted between the orientation degree and tensile strength of PLLA fibers, which means that the oriented structure plays a dominant role to enhance PLLA fibers. PLLA fibers with high performance of 499 MPa and 5.30 GPa in tensile strength and Young’s modulus separately have been realized by the selected spinning parameters. The results provide a theoretical direction for enhancing PLLA fibers by adjusting the structure characteristic via modifying the spinning parameters.