NYLON FIBER: A manufactured fiber in which the fiber forming substance is any long chain synthetic polyamide having recurring amide groups (-NH-CO-) as an integral part of the polymer chain (FTC definition).
The two principal nylons are nylon 66, which is polyhexamethylenedianime adipamide, and nylon 6, which is polycaprolactam. Nylon 66 is so designated because each of the raw materials, hexamethylenediamine and adipic acid, contains six carbon atoms. In the manufacture of nylon 66 fiber, these materials are combined, and the resultant monomer is then polymerized. After polymerization, the material is hardened into a translucent ivory-white solid that is cut or broken into fine chips, flakes, or pellets. This material is melted and extruded through a spinneret while in the molten state to form filaments that solidify quickly as they reach the cooler air. The filaments are then drawn, or stretched, to orient the long molecules from a random arrangement to an orderly one in the direction of the fiber axis. This drawing process gives elasticity and strength to the filaments.
Nylon 6 was developed in Germany where the raw material, caprolactam, had been known for some time. It was not until nylon 66 was developed in the United States that work was initiated to convert caprolactam into a fiber. The process for nylon 6 is simpler in some respects than that for nylon 66. Although nylon 6 has a much lower melting point than nylon 66 (a disadvantage for a few applications), it has superior resistance to light degradation and better dyeability, elastic recovery, fatigue resistance, and thermal stability.
Two other nylons are: (1) nylon 11, a polyamide made from 11-amino-undecanoic acid; and (2) nylon 610, made from the condensation product of hexamethylenediamine and sebacic acid. Nylon 610 has a lower melting point than nylon 66 and the materials for its manufacture are not as readily available as those for nylon 66. Experimental work has been conducted on other nylons.
CHARACTERISTICS: Although the properties of the nylons described above vary in some respects, they all exhibit excellent strength, flexibility, toughness, elasticity, abrasion resistance, washability, ease of drying, and resistance to attack by insects and microorganisms.
The characteristic features of nylon 66 include:
- Pleats and creases can be heat-set at higher temperatures
- More compact molecular structure
- Better weathering properties; better sunlight resistance
- Softer "Hand"
- High melting point (256 °C/492.8 °F)
- Superior colorfastness
- Excellent abrasion resistance
On the other hand, nylon 6 is easy to dye, more readily fades; it has a higher impact resistance, a more rapid moisture absorption, greater elasticity and elastic recovery.
- Variation of luster: nylon has the ability to be very lustrous, semilustrous or dull.
- Durability: its high tenacity fibers are used for seatbelts, tire cords, ballistic cloth and other uses.
- High elongation
- Excellent abrasion resistance
- Highly resilient (nylon fabrics are heat-set)
- Paved the way for easy-care garments
- High resistance to insects, fungi, animals, as well as molds, mildew, rot and many chemicals
- Used in carpets and nylon stockings
- Melts instead of burning
- Used in many military applications
- Good specific strength
- Transparent to infrared light (-12 dB)
END USES: Nylon is used for apparel such as stockings, lingerie, dresses, bathing suits, foundation garments, and wash-and-wear linings; for floor coverings; for tire cord and industrial fabrics; and in-home furnishings such as upholstery fabrics.
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.