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 this demand, 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.
Textronics contribute a significant part of Internet‐of‐Things (IoT), which empowers added functionalities by connecting smart clothing in a secure way for diverse applications. For the development of flexible and stretchable textile‐based electronics, a conductive material (yarn, fabric, etc.) must be used, and fabrication techniques play a vital role that significantly influences electronic textiles’ properties. Textile‐based sensors, electrodes, and other devices seem to be the favorite choice for continuous wearable monitoring due to their low cost, flexibility, and ease of embedding. Integrating smart capabilities into textiles provides substantial benefits in the fields of healthcare, sports, automobile, and military. These developments have a profound influence on the Fourth Industrial Revolution (4IR). This Review presents an in‐depth study of the current state of the art in the area of textile‐based electronics. The design, development, and evaluation techniques are discussed. Certain limitations and research gaps are also addressed regarding this emerging field. Critically, this Review is more application focused and indicates how the recent developments in electronic textiles will soon impact our lives. As these areas have typically been neglected in previous reviews, additional knowledge to the existing literature is provided by bridging the gap between the academic research and commercialization of wearable Textronics.
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.
In this paper, the feasibility of fabricating polypropylene (PP) nanofibres was investigated using conductive additives such as sodium oleate (SO) and sodium chloride (NaCl) during melt-electrospinning. PP of high melt flow index (MFI = 2000) was used with varying amounts of additives. The effects of amount of additives on the fibre diameter and morphology were investigated. The lowest fibre diameters of 0.371 ± 0.106 and 0.310 ± 0.102 lm were achieved with 7 % SO and 5 % NaCl, respectively. The fabrication of nanofibres was attributed to the increase in the electrical conductivity with the introduction of the additives. The increase in the electrical conductivity was greater in the case of NaCl, due to the smaller ionic size of NaCl. Differential scanning calorimetry results showed complex melting behaviour during the heating cycles for the fibres containing SO; and double melting peaks during the second heating cycle for the fibres containing NaCl. X-ray diffraction studies showed the fibres fabricated with the additives contained lower degrees of crystallinity compared to the as-spun fibre and the crystallinity was increased after annealing. The fibres fabricated with the additives contained a-form crystals only which did not change after annealing. The fibres fabricated from pure polymer and with the additives were hydrophobic in nature. The hydrophobicity was marginally decreased with the addition of SO and NaCl.
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.
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