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Core-shell-structured polyvinyl alcohol (PVA)-poly (lactic acid) (PLA) nanofibers combining the hydrophilic trait of PVA and the biocompatibility of PLA were produced using coaxial electrospinning. This allowed the incorporation of AgN[O.sub.3] in the PVA core of the distinct fibers as shown through transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) showed relatively uniform and bead-free fibers with smooth surfaces. Ag-containing fibers show significantly decreased diameters compared with Ag-free samples as a result of the increased conductivity of the spinning solutions with increasing amounts of AgN[O.sub.3]. In a postsynthetic treatment, the AgN[O.sub.3] was reduced forming silver nanoparticles (Ag NPs). Ag NPs of 45 to 90 nm size were located in the PVA core but also on the surface of the core-shell fibers and as individual, agglomerated, and polymer-coated particles of 100-200 nm. Powder X-ray diffraction (PXRD), energy dispersive X-ray spectroscopy (EDX), and UV-vis absorption spectroscopy confirmed the increasing amounts of Ag in the core-shell fibers when using increasing amounts of AgN[O.sub.3] in the spinning solutions. The antibacterial activity of the nanofiber mats against two prokaryotes Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) increased with increasing amounts of Ag, as expected and produces inhibition zones of 1 to 2 mm. KEYWORDS antibacterial, coaxial electrospinning, core-shell fibers, poly (lactic acid), polyvinyl alcohol, silver nanoparticles, 1 | INTRODUCTION Worldwide, microbial infections are a significant and worrying challenge, and the design and synthesis of antimicrobial products for different applications are eminent fields of research. [1-3] Nanomaterials [...]

Carpeting is one of the most efficient approaches to provide both the acoustic and thermal insulation, and improve the comfort of building inhabitants. In the current research work, the acoustic and thermal properties of handmade carpets as one of the commonly used textile products in several countries, especially in Middle-East countries, have been investigated. Aiming to find the optimum weaving condition to maximize the insulation performance of the handmade wool carpets, the weaving variables of knot type, knot density, and pile height were changed. By performing a set of experiments according to the Response Surface Methodology (RSM), the sound absorption coefficient and thermal resistance values were measured for each sample. The statistical analysis showed that the sound absorption and thermal properties of carpets were appropriately described with the linear model. The pile height was the most effective factor for the both sound absorption and thermal resistance responses. Knot density was marginally significant, while the knot type had a negligible contribution. Increasing the height of the pile and knot density led to an increase in sound absorption and thermal resistance. The optimization procedure suggested that within the experimental range, the best acoustic and thermal insulation, can be obtained at knot density of 35 (per 7 cm), and the pile height of 3 cm. [ABSTRACT FROM AUTHOR]

Hydrogels are porous biomaterials widely used in tissue engineering (TE), but they require a mechanism to enhance their mechanical properties. Electrospun nanofibrous yarn (EN yarn) can be a suitable candidate for reinforcing hydrogels. In this study, aiming to improve mechanical performance, hydrogel-based scaffolds reinforced by EN yarns (yarn reinforced hydrogel) were fabricated. The morphological characterization, swelling measurement, and tensile tests were performed to evaluate the physical, mechanical, and biological function of the designed yarn reinforced hydrogel. The measured mechanical properties were used as inputs in the mathematical model of the modified rule of mixtures to predict the mechanical behavior of different yarn reinforced hydrogels, which could be used as scaffolds for different tissues. Cell-scaffold interactions were also evaluated by in vitro assays. This study indicated that adding EN yarns to the neat hydrogel decreased the porosity and swelling, while the tensile strength and Young's modulus were improved. In vitro assays showed that cells had better adhesion and spread on the surface of the yarn reinforced hydrogel than those on the surface of the neat hydrogel. Regarding the improvement in mechanical and cellular properties, the yarn reinforced hydrogel has the potential to be used as a novel scaffold in TE. [ABSTRACT FROM AUTHOR]

In this study, the continuous twisted PLLA yarns were produced using an electrospinning device consists of two oppositely charged nozzles. The electrospinning process was performed at different twist rates. The electrospun twisted yarns were drawn at different extension ratios of 50% and 100% and their morphological and mechanical properties of post-drawn yarns were investigated. The morphological studies at all twist rates shown that uniform and smooth fibers without any bead were formed. Increasing the twist rate up to 240 rpm resulted to a decrease in the average diameter of the fibers in the yarn structure. After uniaxially drawing of the yarns, the average diameter of fibers and thus the yarn diameter decreased. The post-drawing process enhanced the crystallinity of the fibers in the yarn structure. Furthermore, by increasing the extension ratio, the tensile strength and modulus of yarns increased, while the elongation at break (%) decreased., INTRODUCTION The traditional industry of textile is an important part of the world manufacturing industry. Apart from the traditional application of textile materials in clothes and fabrics, recently they have [...]

The stereocomplex formation is a promising method to improve the properties of poly(lactide) (PLA)-based products due to the strong interaction of the side-by-side arrangement of the molecular chains. Recently, electrospinning method has been applied to prepare PLA stereocomplex, which is more convenient. The objective of the current study is to make stereocomplexed PLA nanofibers using electrospinning method and compare their properties and structures with pure poly(l-lactide) (PLLA) fibers. The stereocomplexed fibers were electrospun from a blend solution of high molecular weight PLLA and poly(d-lactide) (1:1 ratio). The morphology of the obtained electrospun fibers was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Differential scanning calorimetry was applied to study their thermal properties and crystallinity. Fourier transform infrared spectroscopy (FTIR) test was conducted on the samples to characterize their chemical properties. The SEM and AFM images indicated that smooth uniform fibers with a cylindrical structure were produced. Besides, the FTIR results and thermal properties confirmed that only stereocomplex crystallites formed in the resulting fibers via the electrospinning method. [ABSTRACT FROM AUTHOR]

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ABSTRACT Poly ( l-lactide) (PLLA) fibrous yarns were prepared by electrospinning of polymer solutions in 2,2,2-trifluoroethanol. Applying spinning from two oppositely charged needles the spontaneous formed triangle of fibers at a grounded substrate could be assembled into fibrous yarns using a device consisting of a take-up roller and twister. The effect of processing parameters on the morphology, diameter and mechanical properties of PLLA yarns was investigated by the response surface methodology (RSM). This method allowed evaluating a quantitative relationship between polymer concentration, voltage, take-up rate and distance between the needles' center and the take-up unit on the properties of the electrospun fibers and yarns. It was found that at increasing concentrations up to 9 wt % uniform fibers were obtained with increasing mean diameters. Conversely, the fiber diameter decreased slightly when the applied voltage was increased. The take-up rate had a significant influence on the yarn diameter, which increased as the take-up rate decreased. The tensile strength and modulus of the yarns were correlated with these variables and it was found that the polymer concentration had the largest influence on the mechanical properties of the yarns. By applying the RSM, it was possible to obtain a relationship between processing parameters which are important in the fabrication of electrospun yarns. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41388. [ABSTRACT FROM AUTHOR]