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Non-wovenNon-woven textiles are those which are neither woven nor knit, for example felt. Non-wovens are typically not strong (unless reinforced by a backing), and do not stretch. They are cheap to manufacture. Non-woven fabric is manufactured by putting small fibers together in the form of a sheet and then binding them either mechanically (as in the case of felt), with an adhesive, or by interlocking them with serrated needles such that the inter-fiber friction results in a strong fabric. Raw material Non-woven materials are nowadays mainly produced from man-made fibers. Two synthetic polymers dominate the market: polypropylene and polyesters (mainly PET). Applications Non-woven materials are used in numerous applications, including: Manufacturing processes Staple non-wovens Staple non-wovens are made in two steps. Fibers are first spun, cut to a few centimeters length, and put into bales. These bales are then dispersed on a conveyor belt, and the fibers are spread in a uniform web by a wetlaid process or by carding. Spunlaid non-wovens Spunlaid non-wovens are made in one continuous process. Fibers are spun and directly dispersed in a web by deflectors. This technique leads to faster belt speeds, and cheaper costs. Several variants of this concept are available, but the leading technology is the Reicofil machinery, manufactured by Reifenhaser (Germany). Bonding Both staple and spunlaid non-wovens would have no mechanical resistance per se without the bonding step. Several methods can be used: - thermal bonding: calendering through heated rollers (called spunbond when combined with spunlaid)
- hydro-entanglement: mechanical intertwining of fibers by water jets
- needlefelt: mechanical intertwining of fibers by needles
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