Textile production

4.3.3. Other developments in spinning
Improved fibre-spinning techniques in melt spinning, wet spinning and dry spinning, and new techniques such as gel spinning, conjugate (bicomponent) spinning and microfibre spinning, have made it possible to produce fibres with characteristics more suitable for use in technical textiles. It is now possible to produce man-made fibres with highly sophisticated non-circular cross-sections, blends of filaments in a yarn having ‘differential shrinkage’, splitting of component filaments, as well as surface treatments to produce a required morphology and topography. As an example, bicomponent fibre technology is mainly used to produce microfibres, binder fibres, self-crim- pable fibres, electro-conductive fibres and heterofil yarns. The three main types of bicomponent fibres are core-sheath, side-by-side and islands-on- sea. Japanese fibre producers – for example, Teijin, Toray and Kuraray – have been pioneers in producing high-functional fabrics from bicomponent fibres.
4.3.4. Developments in coating and lamination
In past few years there have been some interesting developments taking place with regards to intelligent textile materials where the value added function has been achieved by suitable coating and laminating techniques. Among these developments, one can mention breathable and waterproof fabrics, photo luminescent materials, shape memory polymers, phase-change, insulation and light-protective materials.
One of the most significant developments in breathable waterproof fabrics, for example, was the introduction in 1976 of the GORE-TEX rainwear by W. Gore. The active layer, a microporous polymeric film made of expanded polytetrafluoroethylene (PTFE), claimed to contain holes much smaller than the smallest raindrops yet very much larger than a water vapour molecule. This particular microstructure was claimed to give a good barrier against rain and at the same time result in good thermal comfort of the garment because of the removal of high humidity in the microclimate. This was followed by other developments using mainly polyurethane-based microporous coatings, such as in Entrant made by Teijin, and polyester- based non-porous hydrophilic membranes by Sympatex. Since then, numerous developments in microporous polymer structures for use in direct coating, and as a film for laminating into two- or three-layer structures, have taken place worldwide. These microporous structures function by allowing the passage of water vapour molecules (approximately 0.0004 micron in diameter), whereas large diameter (> 100 micron) water drops get blocked by these structures. Water vapour transmission through hydrophilic membranes is achieved by the physical processes of adsorption, diffusion and desorption.