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Stab and puncture resistant body armor is widely used by the law enforcement personnel, security and military in many countries. The primary requirement for the armor is to provide protection against various weapons used in an attack. Comfort properties are given increased importance in many countries and considered the second most important requirement. In this research Kevlar was blended with wool and wool–nylon. The resultant fabrics were coated with silica and their stab and puncture resistance in quasistatic conditions was examined using the universal tensile tester. It was hypothesized that the application of coating will generate higher friction to restrict the lateral movement of yarns, and thus present a higher number of yarns for direct resistance to impact during the attack and dissipating the impact energy, whereas the use of wool and nylon will provide the required ergonomics of wearability and stretch. It was observed that the application of the silica coating helped in improving the resistance to the stab and punctures using weapons such as knife (P1, as specified in NIJ 0115.00), ball and pointed impactors. In the quasistatic tests, the highest value of the maximum resistant force was recorded when the ball was used and the lowest was observed for the knife. Furthermore, the application of coating helped in absorbing impact energy. However, the fabric stiffness increased due to the coating, which will negatively impact the ergonomics and wearability. [ABSTRACT FROM AUTHOR]

In this paper, a novel technique for the fabrication of nanofibres of polypropylene by meltblowing process with the injection of different fluids (such as nitrogen and water) has been explained. Low molecular weight polypropylene polymers were used in this study. The surface morphology of nanofibres was analysed by scanning electron microscopy. It was observed that the use of water gave better results compared to nitrogen for the fabrication of nanofibres. Nuclear magnetic resonance studies revealed similar chemical shifts for polymers and nanofibres, which indicated no change to the chemical functionality of the nanofibres by the application of fluids and high temperature during meltblowing. The mechanical properties of the nanofibres were investigated by using dumb-bell-shaped specimens in a universal tensile tester. The fibres fabricated with nitrogen were weaker and lower in tensile modulus compared to the fibres fabricated with water. The use of a rotating collector increased the tensile strength compared to a stationary collector due to higher degree of fibre alignment in the rotating drum. The tensile strength and modulus values were increased after annealing due to the increase in the crystallinity. The meltblown nanofibres showed hydrophobic nature as indicated by the high values of water contact angle. The hydrophobicity of the nanofibres fabricated with the injection of fluids did not change noticeably from the as-spun fibres fabricated without the fluids. [ABSTRACT FROM AUTHOR]

The feasibility of fabricating polypropylene (PP) nanofibers has been explored by using different additives, such as sodium oleate (SO), poly(ethylene glycol) (PEG) and poly(dimethyl siloxane) (PDMS), during melt electrospinning. PP of high melt flow index (1000) was used with PEG and PDMS for the reduction of the melt viscosity; and it was used with SO for improving the electrical conductivity during melt electrospinning. It was observed that all the additives used in this study helped to reduce the fiber diameter. The most promising additive, SO, was effective in reducing the fiber diameter to the nanometer scale due to the increase in the electrical conductivity. The fiber diameter was decreased by the addition of PEG and PDMS due to the decrease in the melt viscosity. The effect of die shape on the fiber cross-sectional shape was analyzed and an interesting finding is that the die shapes did not have an effect on the cross-sectional shape of the fibers. That is, irrespective of the die shapes (i.e. trilobal, tetralobal, multilobal and circular) used in this study, the cross-sectional shapes of melt electrospun fibers were circular. The distribution of the additives in the fiber was analyzed by energy-dispersive X-ray analysis and was found to be uniform. Tensile tests were performed on single nanofibers with limited success, due to the problems in preparing fiber samples and successfully holding them in the jaws of the testing machine without slippage. [ABSTRACT FROM AUTHOR]

Over the past decade, there has been a tremendous increase in the demand for polymeric nanofibres which are promising candidates for various applications including tissue engineering, protective clothing, filtration and sensors. To address thisdemand, researchers have turned to the development of various techniques such as electrospinning, meltblowing, bicomponent spinning, forcespinning and flash-spinning for the fabrication of polymeric nanofibres. However, electrospinning is the widely used technique for the fabrication of continuous nanofibres. The ability to fabricate nanofibrous assemblies of various materials (such as polymers, ceramics and metals) with possible control of the fibre fineness, surface morphology, orientation and cross-sectional configuration, gives electrospinning an edge over other processes. Although several researches have been done in electrospinning, understanding some of the other processes is still in infancy. In this perspective article, we summarize the fundamentals of various techniques for the fabrication of nanofibres. This paper also highlights a gamut of recent advances in the techniques for nanofibre fabrication. [ABSTRACT FROM PUBLISHER]

The origin of electrospinning as a viable technique for producing nanofibers can be traced back to 1934 when Formhals patented his first invention [1]. In the last few years the work of many researchers have made the electrospinning process suitable for processing of wide variety of biopolymers, engineering plastics, conducting polymers, block copolymers, ceramics and composite materials to produce nanofibers with controllable diameters. Several researchers have attempted to align the fibers in specific patterns and to stack layer-by-layer to produce composites. The aligned nanofibers can be potentially applied in composite materials, reinforcements, electrochemical sensing, bone and tissue engineering. The large surface area to volume ratio and porous structure as compared to the conventional fiber enable these fibers to be used in adsorption of chemicals, military and civilian filtration [2]. [ABSTRACT FROM AUTHOR]