Polyamide fibres were the first synthetic fibres to appear on the market. They were produced for the first time in USA in 1938, as a result of the research which Wallace H. Carothers had started already a decade before with the objective of preparing through synthesis polymers with a structure similar to that of cellulose and silk. The way followed by Carothers was directed at achieving, as an intermediate material for fibre production, a polymer of hexamethylene diamine adipate (salt N) resulting from the reaction between hexamethylene diamine and adipic acid.
This end-product was called nylon 6.6, because its two components have 6 carbon atoms each. However, in the same year 1938, Paul Schlack, taking advantage of the error of judgement of Carothers who claimed that caprolactam could not polymerise to form polyamides, succeeded in obtaining all the same a nylon - this time named nylon 6, being made up only of one product with 8 carbon atoms — without infringing the American patents. In the following years, his discovery was extensively exploited in Germany, where the product was called Perlon. Nylon 6.6 and 6 were later produced, under licence or through patent acquisition, also in other European countries, Italy included.
The polyamide fibre was rightly regarded as the "wonder" fibre by virtue of its countless end-uses: stockings and pantyhoses, swimwear, ladies' underwear, corsetry, linings, umbrellas, outerwear, raincoats and floorcoverings. Nylon is also used for several technical applications: tyre cords, conveyor belts, filters, fishing nets, cordage, parachutes, safety belts, inflatable boats and other sport articles.
More recently, this fibre has been further developed to originate continuous filament yarns composed of very fine filaments (abt. 1 dtex) as flat yarns, false-twist textured and air-jet textured yarns, which are used in the production of a new generation of high performance fabrics which meet not only quality and fashion requirements, but also take into account the physiological properties needed by clothing (snowsuits).
This yarn has good dimensional stability to washing, impermeability to water and to air, permeability to steam, good heat transfer, silky and soft handle, good dye yield; all these factors contribute to make this material particularly suited to sport and leisure wear.
The polyamide family includes also other types of nylon: : nylon 4 and 11.
More and more important is becoming the category of polyamide-imides, known also as
aramid fibres. Of relatively recent development, these high-tech fibres, which resist
highest temperatures and even flame and have excellent resistance to chemicals, are suited to technical and industrial uses.
A specialty fibre with optimal comfort properties belongs to the new category of the polyoxamide fibres. This fibre, which is produced in Italy, is particularly suitable for 20- 50% blends with wool, angora, cashmere, alpaca, cotton, viscose staple and synthetics, thus resulting ideal for knitwear.
For dyeing nylon 6.6. usually acid and disperse dyes are preferred, although many other dyestuff classes can be used. Dyestuffs suitable for nylon 6 are disperse and microdisperse, acid, mordant acid, premetallized, synthetic (on the fibre) dyes. The overall world output of polyamide fibres in 1998 was about 4.0 million tons (about 16% of the total production of synthetic fibres altogether).
