Rajiv Padhye

Recent advances in nanofibre fabrication techniques

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.

RFID in textile and clothing manufacturing: technology and challenges

In the field of textile and clothing, radio frequency identification (RFID), which is one of the most promising technological innovations, is used in manufacturing, inventory control, warehousing, distribution, logistics, automatic object tracking and supply chain management. Various retailers and manufacturers (of clothing as well as consumer goods) such as CVS, Tesco, Prada, Benetten, Wal-mart and Procter & Gamble, are now implementing the technology and exploring the impact of the technology on their business. RFID technologies may improve the potential benefits of supply chain management through reduction of inventory losses, increase of the efficiency and speed of processes and improvement of information accuracy. The basic of success lies in understanding the technology and other features to minimize the potential problems. Although the technology existed for several years, the technological challenges and cost issues are the major hurdles for the widespread use of RFID. In this paper, the authors have addressed the technology of RFID and various applications related to inventory management, production control, retail management, brand segregation etc. in textile and clothing industry. In addition, the disadvantages, challenges and future directions of RFID technology have also been highlighted.

Effect of viscosity and electrical conductivity on the morphology and fiber diameter in melt electrospinning of polypropylene

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.

The role of mass customisation in the apparel industry

During the past decade, the textile and apparel industries around the globe have been trying to adjust to a rapidly changing business environment. While the manufacturing bases have moved into the developing countries, the developed countries have gone high tech in a bid to maintain an edge over the low-cost competitors. Apparel purchasing is moving out of the physical domain into the virtual domain and mass customisation seems to be the only way to win and retain buyers. Ten years back, jeans maker Levi Strauss announced something just as revolutionary: It will begin offering customised versions of its classic denims to fit every womans body type. The term Mass customisation well defined the aforementioned process of providing fit garments according to the body size. Mass customisation in the apparel industry is a revolutionary one. It provides a product according to the choice of the consumers. This paper reviews the role of mass customisation in the competitive apparel industry. The requirements and future challenges for mass customisation are also discussed.

Application of Wool in High-velocity Ballistic Protective Fabrics

The protective power of typical aramid-based ballistic fabrics, when assembled into multi-layered panels designed to defeat high-velocity ballistic impacts, can be improved if wool is incorporated into the weave structure. Although the synthetic is still the primary energy-absorbent material, the wool plays a complementary role by increasing resistive interactions between the yarns and filaments. Wool restricts the lateral separation of the synthetic yarns and ensures that more directly impacted yarns are held in place to dissipate the impact energy. Wool increases the energy-absorption mechanism of yarn pull-in by increasing the longitudinal friction along the yarns/filaments, in particular near the free edges of the fabric layers. The wool absorbs water that may otherwise lubricate synthetic filaments and so improves the wet performance. Ballistics tests have shown that synthetic fabrics blended with wool can at least match the dry or wet ballistic performance of an equivalent pure Kevlar fabric when tested under National Institute of Justice (NIJ) Ballistic Standard Level III A. The inclusion of the wool can significantly improve the tear strength of pure synthetic ballistic fabrics.

The thermal protection and comfort properties of aerogel and PCM-coated fabric for firefighter garment

The study evaluates the simultaneous use of aerogel and phase change material (PCM) on the face cloth of thermal liner in firefighter’s protective garment. Aerogel is commonly used to resist incoming heat flux in the field of high heat protection and to prevent the loss of body heat in the cold environment clothing. In high heat protection clothing, aerogel not only resists the incoming heat fluxes but also blocks the outbound body heat. As a result the wearer suffers from internal increase of body temperature. Previous studies identified the potential use of aerogel in firefighter’s protective clothing. However there was no clear approach to resolve the problem associated with body heat release. Current study focuses on the problem by applying PCM along with aerogel on fabric. The ambient-side of a thermal liner face cloth was coated with silica aerogel particles; meanwhile, the next to skin side was coated with PCM/aerogel composite powder. The new thermal liner revealed superior thermal protection and comfort. It extended the time to reach pain threshold and increased the pain alarm time. The Fourier transform infrared analysis of the aerogel/PCM composite powder showed the presence of PCM in nanoporous aerogel particles while the differential scanning calorimeter quantified the heat absorbing capacity of the new composite powder. Scanning electron microscope, air permeability tester, and jPOR macro of ImageJ software were used for the surface characteristics and porosity analysis of coated liner. The thermal stability of the composite powder was investigated through an infrared thermal camera. No dripping or form deterioration was observed when the composite powder was heated over a temperature three times above the melting temperature of the pure PCM.

Preparation, characterisation, and in vitro evaluation of electrically conducting poly(ɛ-caprolactone)-based nanocomposite scaffolds using PC12 cells.

In the current study, we describe the synthesis, material characteristics, and cytocompatibility of conducting poly (ɛ-caprolactone) (PCL)-based nano-composite films. Electrically conducting carbon nano-fillers (carbon nano-fiber (CNF), nano-graphite (NG), and liquid exfoliated graphite (G)) were used to prepare porous film type scaffolds using modified solvent casting methods. The electrical conductivity of the nano-composite films was increased when carbon nano-fillers were incorporated in the PCL matrix. CNF-based nano-composite films showed the highest increase in electrical conductivity. The presence of an ionic solution significantly improved the conductivity of some of the polymers, however at least 24 h was required to absorb the simulated ion solutions. CNF-based nano-composite films were found to have good thermo-mechanical properties compared to other conducting polymer films due to better dispersion and alignment in the critical direction. Increased nano-filler content increased the crystallisation temperature. Analysis of cell viability revealed no increase in cell death on any of the polymers compared to tissue culture plastic controls, or compared to PCL polymer without nano-composites. The scaffolds showed some variation when tested for PC12 cell attachment and proliferation, however all the polymers supported PC12 attachment and differentiation in the absence of cell adhesion molecules. In general, CNF-based nano-composite films with highest electrical conductivity and moderate roughness showed highest cell attachment and proliferation. These polymers are promising candidates for use in neural applications in the area of bionics and tissue engineering due to their unique properties.

Thermal comfort properties of Kevlar and Kevlar/wool fabrics

Recent research on ballistic vests has focused on comfort performance by enhancing thermal comfort and moisture management. Kevlar/wool fabric has been developed as a potential material for ballistic vests. This study investigates the thermal comfort properties of woven Kevlar/wool and woven Kevlar ballistic fabrics. In this context, the thermal resistance, water-vapor resistance, moisture management performance, air permeability and optical porosity of 100% Kevlar and Kevlar/wool ballistic fabrics were compared. The effects of fabric physical properties on laboratory-measured thermal comfort were analyzed. This study also presents the fabric bursting strength and tear strength for comparison. Experimental results showed a clear difference in thermal comfort properties of the two fabrics. It was found that Kevlar/wool possesses better moisture management properties and improved mechanical properties than Kevlar fabric.

Fabrication and Characterisation of Nanofibres by Meltblowing and Melt Electrospinning

Fabrication of nanofibres has become a growing area of research because of their unique properties (i.e. smaller fibre diameter and higher surface area) and potential applications in various fields such as filtration, composites and biomedical applications. Although several processes exist for fabrication of nanofibres, electrospinning is considered to be the simplest. Most of the research in electrospinning is based on solution rather than melt. The feasibility of fabricating nanofibres of polypropylene (PP) by meltblowing and melt electrospinning has been investigated in this paper. In meltblowing different fluids such as air and water were fed at different inlets along the extrusion barrel for the fabrication of nanofibres whereas in melt electrospinning it was achieved by using different additives. The results obtained by using water in meltblowing were better with respect to the morphology and fibre uniformity compared to air. In melt electrospinning although all the additives (i.e. sodium oleate (SO), polyethylene glycol (PEG) and polydimethyl siloxane (PDMS)) helped in reducing the fibre diameter, only SO was effective to reduce the diameter down to nanoscale. It was concluded that both the solvent-free processes have the potential to substantially increase the production of nanofibres compared to solution electrospinning.

Structural and mechanical properties of polypropylene nanofibres fabricated by meltblowing

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.