Textile production

4.3.1. Developments in staple yarn production
Ring spinning, initially developed in America in the 1830 s, is currently the most widely used yarn production method. Because of the particular attributes of ring spun yarns – for example, superior yarn quality – its popularity has survived the commercialization of much faster technologies, such as rotor spinning, which was commercially introduced in 1967 and can attain much higher twisting speeds than ring spinning. The roving process needed in ring spinning is eliminated in rotor spinning, further reducing the production costs. Friction spinning is an open-end spinning technique. Instead of using a rotor, two friction rollers are used to collect the opened-up fibres and twist them into the yarn. Air-jet spinning technology was first introduced by DuPont in 1963, but it has only been made commercially successful by Murata since 1980. This technology is used mainly for spinning short-staple fibres, especially cotton and polyester blends. Novel yarn-spinning technologies are commercially available today for producing hybrid yarns for various applications. Two technologies are used to manufacture hybrid yarns:
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conventional spinning by intimately blending two different yarns
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core yarn spinning making a core of a certain fibre type covered with a sheath of a different fibre type.
One can thus combine the functions of two different fibre qualities to produce fabric of varied functions; for example, the core can be made of p-aramid, the sheath of m-aramid, cotton or polyester. Sensitive core-materials can be protected by sheath fibres. For industrial applications wrapping provides unique opportunities to combine yarns using a core and wrap structure. The predominant use of this structure is in industrial-based applications, including cut-resistant gloves and conveyer belts.
4.3.2. Developments in filament yarn production
For many applications, extruded thermoplastic filaments are textured in order to gain increased bulkiness, porosity, softness and elasticity. The principles of the main texturing methods have evolved from false twisting to stuffer box, air-jet and knit-de-knit successively. Hot-melt resin coating of yarns is another interesting technique and is accomplished by using solid resin. Lower viscosity resins, especially hot-melt adhesives, can be applied on a reinforcing yarn by crosshead extrusion, which is similar to insulating a wire. Such coatings completely encapsulate the yarn. The coating type and amount is defined by the application of the yarn and the bond strength needed. Novel yarns can then be made in to hybrid fabrics by a weaving, weft knitting or warp knitting process, and further processed using heat treatment, or calendered to make technical fabrics or flexible composites.