Nylon (polyamides): Synthetic fibre forming polyamides are also termed as Nylons. Therefore, Nylon is well known in the textiles. Nylons are those polymers which contains a repeating amide linkage. The nylons have been named on the basis of the number of carbon atoms in the monomer molecules. Usually four types of nylons are prepared:

1.                 Nylon6: This is prepared by ring opening polymerization by self: polyconensation of caprolactum which contains 6 carbon atoms. The process occurs in 4 steps.  

(1)                         Cyclohexane is oxidized to cyclohexanone

(2)                         Cyclohexanone converts cyclohexanoneoxime by treatment with hydroxylamine NH₂OH.

(3)                         This cyclohexanoneoxime undergoes Backmann rearrangement to give caprolactum in presence of H₂SO₄. 

(4)                         Ring opening polymerization of caprolactum to give Nylon: 6.

2.                 Nylon: 66: This is prepared by the condensation of polymerization of Adipic acid and hexamethylene diamine in 1: 1 molar ratio.  

3.                 Nylon:6, 10: This is prepared by self condensation of polymerization of hexamethylene diamine and sebasic acid.

4.                 Nylon: 11: This is prepared by self: condensation of W. It is more expensive than other nylons.

Properties:

1.                 They are soluble in phenol and formic acid, while insoluble in common organic solvents like benzene, ethylated spirit, acetone etc.

2.                 The polymer chains are held together by hydrogen bonds. Thus nylons possesses high crystalline which imparts high strength, high melting point (160 to 264⁰C) elasticity, toughness etc.

3.                 Nylons are whitish, translucent and possess good high thermal stability and good abrasion-resistance.

4.                 It can retain good mechanical properties up to 150 degree centigrade.

5.                 They are sterilizable.

Uses:

1.                 Nylon-6 is mainly used for making tyre cords and non woven fabrics.

2.                 Due to sterilisability, they are used in medicine and pharmacy.

3.                 Nylon-6, 6 is used for manufacture of fibre cloth, ropes, carpets and undergarments, socks, etc.

4.                 Nylon-6, 6 is used in gears, bearings, brushes etc.

5.                 Nylon-6, 10 is suitable for monofilaments which are used for bristles, brushes and sporting equipments.

6.                 Nylon-11 is used in the preparation of textile fibres and threads; it is also used for making bearing and gears due to its self lubricating properties.