Polyamides Fiber

Polyamides are macromolecules whose structural units are interlinked by the amide linkage (-NHCO-).

Synthetic polyamides with structural unit derived predominately from aliphatic monomer are members of the generic class of nylons; where as synthetic polyamides in which at least 85% of the amide functions are directly adjacent to aromatic structures have been designated aramides.

The commercially important types of polyamides fiber are:

1. Nylon 6,6
2. Nylon 6
3. Nylon 11
4. Nylon6,10

Raw materials for production of:

1. Nylon 6: 6 amino caproic acid.
2. Nylon 6,6: Hexa-methylene diamin and adipic acid.
3. Nylon 6,10: Hexa-methylene diamin and sebasic acid.
4. Nylon 11: 11-amino undecanoic acid.
5. Nylon 7: Amino Heptanoic acid.

Feature of Nylon:

1. Diameter: 14μm to 24μm.
2. Color: Slightly off-white.
3. Moisture regain: 3.5 to 5.0%.
4. Hand feel: Soft and smooth.
5. Abrasion resistance: Excellent.

Properties of Nylon:

1. Tenacity: 4-9 gm/den (dry), in wet 90% of dry.
2. Elasticity: Breaking extension 20-40%.
3. Dimensional stability: Good.
4. Softening point: Nylon 6,6=229ºC, Nylon 6= 149ºC.
5. Melting point: Nylon 6,6= 252ºC, Nylon 6= 215ºC.

Chemical properties of Nylon:

1. Acid: Nylon 6,6 is attacked by mineral acid. Dissolve in concentrated formic acid.
2. Bleach: Not affect by normal oxidizing and reducing bleaches but harmed by strong bleaches.
3. Alkali: Stable again alkali.
4. Light: No discoloration.
5. Flammability: Burns slowly.

Difference between Nylon 6 and Nylon 6,6:

Nylon 6	Nylon 6,6
1. Melting point is 205ºC	1. Melting point is 250ºC
2. Dye affinity high	2. Dye affinity is low.
3. Fatigue resistance high	3. Fatigue resistance is low.

End use:

1. Apparel use: Used for gloves, hosiery fabric.
2. Domestic use: Home furnishing, carpets, upholstery, ropes.
3. Industrial use: Fishing nets, sewing threads, belt of various machine.