Polyamide:
In September 1931, American chemist Wallace
Carothers reported a research carried out in the laboratories of the DuPont
Company on “giant” molecules called polymers. He focused his work on a fiber
referred to simply as “66,” a number derived from its molecular structure. By
1938, Paul Schlack of the I.G. Farben Company in Germany, polymerized
caprolactam and created a different form of the polymer, identified simply as
nylon “6.” DuPont began commercial production of nylon in 1939. The first
experimental testing used nylon as sewing thread, in parachute fabric, and in
women's hosiery.
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.
Production
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:
·
Specific
weight
Nylon 6 : 1.13 - 1.15; Nylon 6.6 : 1.13 - 1.15; Nylon 6.10: 1.09;
Nylon 6.12: 1.09; Nylon 11: 1.04 to 1.05;
·
Moisture regain 7 %
·
Elongation 50 %
·
Melting point - Nylon 6: 210 - 220°C Nylon
6.6: 255-265°C Nylon 6.10: 220°C; Nylon 6.11: 195-219°C;
·
Relatively unaffected by: hydrocarbons, esters,
ethers, oils, concentrated alkalis
·
Decomposed by concentrated mineral acids,
halogens
·
Combustion melts, darkens, finally burns with
a small flame, easy to extinguish, giving a white smoke Permeability to gases
O2 ... 0.04 CO2.. 0.16 to 0.20 N2 ... 0.01
·
Elastic modulus- Nylon 6: 200 to 300; Nylon
6.6: 250; Nylon 6.10: 400; Nylon 11 500 (daN/mm^2)
Polyamide Characteristics:
Exceptionally strong , Elastic,
Abrasion resistant , Lustrous , Easy to wash, Resistant to damage from oil and
many chemicals, Can be pre-colored or
dyed in wide range of colors, Resilient,
Low in moisture absorbency, Filament yarns provide smooth, soft,
long-lasting fabrics
Applications:
Apparel:
Blouses, dresses, foundation garments, hosiery, lingerie, underwear, raincoats,
ski apparel, windbreakers, swimwear, and cycle wear
Home Furnishings: Bedspreads, carpets, curtains,
upholstery
Industrial and Other Uses: Tire cord, hoses, conveyer and
seat belts, parachutes, racket strings, ropes and nets, sleeping bags,
tarpaulins, tents, thread, fishing line
