POLYOLEFIN

any of a class of organic substances prepared by the addition polymerization of olefins (hydrocarbons containing one double bond per molecule), especially ethylene and propylene. In textiles, polyolefin denotes synthetic fibre composed of at least 85 percent by weight of polyethylene or polypropylene. Trademarked fibres in this group include DLP, Herculon, Polycrest, and Vectra. Polyolefins were originally used for various plastic items and films; the fibres were not developed until the mid-1950s. The strength of polyethylene fibres varies with type, ranging from that of nylon-6,6 to somewhat less. Polypropylenes can withstand about the same range of loads, again varying with type. Polyethylenes can be stretched about 10-40 percent beyond their original length and polypropylenes from about 15 to 30 percent, with some types having elongation up to 50 percent. Fibres can return to about 90-98 percent of their original length when stretched by about 5 percent. The polyolefins absorb very little moisture. Polyethylenes melt at 110-140 C (230-280 F) and polypropylenes at about 165-175 C (330-350 F). Most polyolefins lose some strength upon prolonged exposure to sunlight. The fibres are not usually affected by age, provided moderate temperatures are maintained, and they have high resistance to most chemicals. They can be washed in strong alkaline solutions and can be dry-cleaned with most common cleaning solvents. Resistance to attack by insects and microorganisms is high, and the fibres are good electrical insulators. The polyolefins are used, alone or in blends, in hosiery, sportswear, and undergarments and in pile fabrics. They are also used in such home furnishings as upholstery, outdoor furniture, and rugs and carpeting, particularly indoor-outdoor types for both residential and public area use. Industrial applications include filters, marine cordage, automobile seat covers, electrical insulation, and carpet backing.