Styrene‐β‐C14 has been polymerized (1) thermally at 99°, (2) with benzoyl peroxide at 51°, and (3) with stannic chloride at 25°. The C14‐labeled monomer was found to react (1) 91.8%, (2) 91.5%, and (3) 95.0% as fast as the nonradioactive styrene under these conditions. When styrene‐α‐C14 was polymerized (1) thermally at 99° and (2) with stannic chloride at 25°, the radioactive monomer reacted 97.0% and 100% as fast as nonradioactive styrene. These results are interpreted in terms of the propagation step of the reaction.
Most elastomeric fibers are currently produced from either natural rubber or segmented polyurethane polymers. The elastic properties or rubber fibers derive from chemical cross‐links formed by vulcanization of either sheets or extruded threads. The segmented polyurethanes, called spandex fibers, are linear block copolymers with relatively long weakly interacting segments that are interconnected by shorter blocks in which intermolecular interactions are strong. Rubber fibers are formed either by slitting vulcanized sheets or by extruding latex into a coagulation bath followed by heating to vulcanize. Spandex fibers are most commonly formed by passing polymer solution through a spinneret followed by removal of solvent; certain spandex compositions can be formed into fibers by melt extrusion. These fibers are normally blended with hard fibers such as nylon, polyester, or cotton to form fabrics with desirable stretch and recovery characteristics. Stabilizers must be included with elastomeric fibers to provide adequate protection from exposure to heat, sunlight, atmospheric pollutants, and active chlorine materials. The unique properties and availability in fine sizes compared to rubber has recently allowed extensive penetration of spandex fibers into hosiery and sportswear markets.
Elastomeric fibers can be made from natural or synthetic polymeric materials that provide product with high elongation, low modulus, and good recovery from stretching. These fibers are made primarily from polyisoprenes (natural rubber) or polyurethanes and to a lesser extent, segmented polyesters. In the United States the generic designation spandex has been given to a manufactured fiber in which the fiber‐forming substance is a long‐chain synthetic polymer comprised of at least 85% of a segmented polyurethane. Manufacture of cut rubber and extruded latex thread are discussed. Spandex fiber can be produced by four processes: melt extrusion, reaction spinning, solution dry spinning (the most common method) and solution wet spinning. Uses for cut thread and extruded latex are as a covered rubber in narrow fabrics, braids, surgical hosiery, and strip lace. Spandex fibers are used extensively in sportswear and hosiery products.
Mechanical Properties Manufacture Chemical Properties Economic Aspects Uses
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