Electrospun nanofibrous webs are important in nanotechnology applications due to their high surface area and interconnected porosity. In this study, the effect of electrospinning duration on some physical and mechanical properties of polyurethane (PU) electrospun webs is investigated for potential applications such as protective clothing and membranes. The results show that the thickness and weight of webs and subsequently their tensile strength increase linearly with the electrospinning duration. Air permeability of nanofibrous webs decrease and hydrostatic pressure increases nonlinearly while water vapor permeability remains constant. This work shows that air permeability of PU webs follows Fick's law of diffusion. Some regression models have been proposed to describe electrospun membranes behavior. The results of this investigation indicate that this new generation of nanofibrous materials has a good potential for application as membrane in protective clothing. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125: [4135][4136][4137][4138][4139][4140][4141] 2012
An electrospinning technique based on the use of two oppositely charged nozzles was applied to fabricate continuous twisted yarns of poly(L-lactide) (PLLA) nano/micro fibers. In this study, the effect of solvent on the electrospinning of PLLA fibrous yarns was investigated. For this purpose, yarns were electrospun using chloroform, dichloromethane or 2,2,2-trifluoroethanol as solvents at a PLLA concentration of 7 wt%. The analysis of the morphology, diameter, crystallinity and mechanical properties of electrospun yarns revealed that the vapor pressure of the solvent plays an important role. Whereas the fiber diameter decreased, the crystallinity of the fibers increased using a solvent with lower vapor pressure. In addition, mechanical properties (e.g., tensile strength and modulus) revealed that the yarns composed of fibers with smaller diameters showed higher tensile strength and modulus. In summary, fine-tuning solvent properties resulted in a modulation of fiber diameter, crystallinity, and thereby yarn mechanical properties, and are important factors to consider in the fabrication and application of electrospun yarns.
Waterproof textiles have wide applications in many fields such as sportswear, protective clothing, and orthopedic dressing. Breathability is an important factor of clothing comfort. Nanofibrous layers have application in these fields due to their interconnected porous area and high surface area. In this work, two different nanofiber layers were fabricated and examined as waterproof and breathable layers. Polyurethane (PU) and PU/nylon 66 (hybrid) nanofiber layers were produced via electrospinning set up with different electrospinning durations. Some of the samples' characteristics such as tensile strength, microindentation, air permeability, water vapor permeability (WVP), and contact angle of water were investigated. Moreover, a novel approach was applied for determining the performance of layers against acidic water to simulate acidic rain. The results show that the tensile strength, indentation force, and acidic waterproof ability of the layers increased with increasing the process duration, that is, while air permeability was decreased simultaneously. This work shows that the required force for indentation and strength of the hybrid layer was less than that of PU nanofiber layer. Also, the electrospun hybrid layers show better air permeability than the PU membrane but still have lower WVP, which affects the breathability of the layer. C 2015 Wiley Periodicals, Inc. Adv Polym Technol 2016, , 21568; View this article online at wileyonlinelibrary.com.
In this study, twisted drug-loaded poly(L-lactide) (PLLA) and hybrid poly(L-lactide)/poly(vinyl alcohol) (PLLA/PVA) yarns were produced using an electrospinning technique based on two oppositely charged nozzles. Cefazolin, an antibiotic drug was incorporated in the yarn fibers by addition to the PLLA electrospinning solution. Morphological studies showed that independent of the twist rate, uniform and smooth fibers were formed. The diameter of the electrospun fibers in the yarns decreased at higher twist rates but produced yarns with larger diameters. At increasing twist rates the crystallinity of the fibers in the yarns increased. In the presence of cefazolin the fiber diameter, yarn diameter and crystallinity were always lower than in the non-drug loaded yarns. In addition the yarn mechanical properties revealed a slightly lower strength, modulus and elongation at break upon drug loading. The effect of the twist rate on the cefazolin in vitro release behavior from both PLLA and hybrid yarns revealed similar profiles for both types of drug-loaded yarns. However, the total amount of drug released from the hybrid PLLA/PVA yarns was significantly higher. The release kinetics over a period of 30 d were fitted to different mathematical models. Cefazolin release from electrospun PLLA yarns was governed by a diffusion mechanism and could best be fitted by Peppas and Higuchi models. The models that were found best to describe the drug release mechanism from the hybrid PLLA/PVA yarns were a first-order model and the Higuchi model.
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