A polyamide fibre is defined by BISFA as being "a fibre composed of linear macromolecules having in the chain recurring amide linkages, at least 85% of which are joined to aliphatic or cycloaliphatic units". There are many polyamide fibres made but only two, described below, are made in significant quantities. The first fibres made from polyamide polymers were produced in 1938 in the USA and Germany. In the USA the raw materials, which were used to produce the polymer, were adipic acid and hexamethylene diamine. Since both chemicals contain 6 carbon atoms the new polymer was named polyamide 6.6. In Germany caprolactam was polymerised to produce a different fibre known as polyamide 6.
To produce fibres from the polyamide polymers the molten polymer is pumped through spinneret holes at a temperature approaching 300 degrees C to form filaments that are cooled and solidified in a quench air stream. If filament yarn is being produced the filaments are then oiled and wound onto bobbins.
If staple fibres are being produced, very many filaments are bundled together to form a tow which is subsequently stretched, crimped and cut to the desired length.
Properties and End-Uses
In weaving the main end-use is for outerwear and technical fabrics like airbags and capply for tyres. In knitting, stockings, hosiery, tights and outerwear are important outlets. Carpets and ropes are also important sectors.