POLYETHYLENE FIBER: A manufactured fiber made of polyethylene, often in monofilament form as well as continuous filament yarns and staple. Ethylene is polymerized at high pressures and the resulting polymer is melt spun and cold drawn. It may also be dry-spun from xylene solution.
CHARACTERISTICS: Polyethylene fibers have a low specific gravity, extremely low moisture regain, the same tensile strength wet and dry, and are resistant to attack by mildew and insects.
These qualities have made polyethylene fiber suitable for industrial applications, geotextiles, outdoor furniture, and similar applications. Polyethylene fiber does not dye, and in most cases, it is colored by the addition of pigments and dyes to the material prior to spinning. It has a low melting point, a property that has restricted its use in apparel.
POLYPROPYLENE FIBER: A manufactured, olefin fiber made from polymers or copolymers of propylene. Polypropylene fiber is produced by melt spinning the molten polymer, followed by stretching to orient the fiber molecules.
CHARACTERISTICS: Polypropylene fibers have a number of advantages over polyethylene fibers in the field of textile applications. The degree of crystallinity, 72 to 75%, results in a fiber that is strong and resilient, and does not fibrillate like high-density polyethylene. Polypropylene has a high work of rupture, which indicates a tough fiber, and may be made with tenacities as high as 8.0 to 8.5 grams per denier.
The melting point of polypropylene is 165°C, which is low by comparison with nylon or polyester, but is high enough to make it suitable for most textile applications. So light that it actually floats, polypropylene fiber provides greater coverage per pound than any other fiber. It is highly resistant to mechanical abuse and chemical attack.
END USES: Polypropylene fibers are widely used in industrial, carpet, and geotextile applications. They have found important uses in fishing gear, in ropes, and for filter cloths, laundry bags and dye bags. The excellent chemical resistance of polypropylene fiber is of advantage in the filtration and protective clothing fields. Fibrillated polypropylene yarns are widely used in indoor-outdoor carpets. Staple fiber finds application in blankets, pile fabrics, underwear, and industrial fabrics; it is being developed for carpets, candlewicks, knitted outerwear, hand-knitting yarns, and upholstery.