"Nylon Fabric: Polyamide PA6 PA66 Properties, History, Denier, and DuPont Invention"

Nylon is a family of synthetic polyamide fibers, and it stands as the first truly synthetic fiber ever produced. Its invention at DuPont in 1935 by a team led by Wallace Hume Carothers marked a watershed moment in materials science, demonstrating that polymers could be rationally designed and synthesized in the laboratory to produce fibers with properties superior to natural alternatives.

Invention and History

Wallace Carothers joined DuPont's fundamental research program in 1928. By 1930, his team had synthesized the first synthetic rubber (neoprene), and they turned their attention to synthetic fibers. The breakthrough came when Carothers and his colleague Julian Hill discovered that a molten polyester could be drawn into strong, silky fibers, but the product's low melting point made it impractical. Shifting to polyamides, the team synthesized the first nylon polymer in February 1935.

DuPont chose not to patent the term "nylon," allowing it to become the generic name for polyamide fibers. After initial commercial applications in toothbrush bristles and fishing line, nylon stockings debuted at the 1939 New York World's Fair and went on sale in May 1940. Sales reached 64 million pairs in the first year alone, with women lining up for limited supplies. During World War II, nylon production was diverted to parachutes, ropes, and tire cords for military use.

Chemical Structure: PA6 vs PA66

Nylon refers to two primary polyamide types used in textiles. Nylon 66 (PA66) is produced from hexamethylene diamine and adipic acid, each containing six carbon atoms, hence the "66" designation. Nylon 6 (PA6) is produced from caprolactam, a molecule with six carbon atoms per monomer. Both were discovered in the 1930s, with PA66 by DuPont and PA6 by German chemist Paul Schlack at IG Farben.

PA66 has a slightly higher melting point (255 to 265 degrees Celsius) compared to PA6 (215 to 225 degrees Celsius) and marginally better tensile strength and abrasion resistance. PA6 has better elasticity, dyeability, and moisture absorption. Both types are used for apparel, but PA66 dominates in high-tenacity applications such as military and outdoor gear, while PA6 is more common in hosiery, sportswear, and carpets. The practical melting range for nylon fabrics is approximately 190 to 260 degrees Celsius depending on type and processing.

Properties and Performance

Nylon fibers have high tenacity, ranging from 4.5 to 9.0 grams per denier depending on type and processing, making nylon one of the strongest textile fibers relative to its weight. Nylon has exceptional abrasion resistance, the highest of any textile fiber, and excellent elasticity with elongation at break of 20 to 40 percent.

Nylon absorbs more moisture than polyester, approximately 4 to 7 percent of its weight at standard conditions, making it more comfortable against the skin in apparel applications. However, this moisture absorption causes dimensional change and reduces strength when wet by roughly 10 to 15 percent. Nylon is resistant to alkalis, most organic solvents, and biological degradation by molds and insects. It degrades under prolonged UV exposure and will yellow and lose strength without UV-stabilizing additives.

Denier Measurement

Fabric weight and fiber fineness for nylon are commonly measured in denier, where one denier equals the mass in grams of 9,000 meters of fiber. A single nylon filament of 1 denier weighs 1 gram per 9,000 meters. Ultralight nylon fabrics are rated at 7 to 15 denier, standard lightweight fabrics at 20 to 40 denier, midweight at 70 to 100 denier, and heavy-duty fabrics at 200 to 1,000 denier. Lower denier fabrics are lighter and more packable; higher denier fabrics are stronger and more abrasion-resistant.

Ripstop and Cordura

Ripstop nylon is a woven fabric incorporating a reinforcement grid of heavier threads at regular intervals, typically every 5 to 8 millimeters in both warp and weft directions. The grid pattern prevents tears from propagating by stopping rips at the reinforced intersections. Ripstop nylon originated in military parachute fabrics and is now standard for outdoor gear, tents, flags, and kites.

Cordura is a brand of high-tenacity nylon fabric developed by DuPont in 1966 and now owned by Invista. Cordura fabrics use air-jet textured nylon yarns that are abrasion-resistant, with durability ratings 2 to 4 times that of standard nylon at equivalent denier. Cordura is available in weights from 330 denier to 1,000 denier and beyond and is the benchmark fabric for military equipment, motorcycle apparel, luggage, and workwear, where extreme durability is the primary requirement.