Polyamides

Polyamides are polymers which contain recurring amide

groups as integral parts of the main polymer chain.

Synthetic polyamides are made by a condensation reaction

taking place between small molecules in which the linkage

of molecules occurs through the formation of amide

groups.

Types of polyamide —

•       Nylon

•       Aramide

Aramide :

Aramide is a long chain synthetic polymer in

which at least 85% of amide linkages are directly

attached to two aromatic rings of a long chain

synthetic polyamide.

Classification:

•      Kevler

•      Nomex

 Nylon:

Nylon was the first man made organic textile fibre made

wholly from raw materials from the mineral kingdom. Nylon

is a manufactured fibre in which the fibre forming

substance is any long chain, synthetic polyamide having

recurring amide groups (-CO-NH-) as an integral part of the

molecular chain.

There are different types of nylon —

•      Nylon-6, Nylon-6,6, Nylon-6,10, Nylon-11, Nylon-7, Nylon 9.

•      Why this amide is called Nylon 6,6:

•      Nylon 6,6 denotes that there are two monomers, each containing six carbon

•      atoms, which ate required to form the polymer of this type of nylon.

•      Nylon 6:

•       Nylon 6 fibre is spun from Polycaproamide, a polyamide made by the self

•      condensation of 6 Amino Caproic acid or its lactam.

•      Caprolactam:

•      CH2(CH2)4CONH                  -NH(CH2)5-CONH(CH2)5CONH(CH2)5-

•                                                                Nylon 6

Raw materials for production of:

–     Nylon 6                : 6 amino caproic acid / caprolactam.

–     Nylon 6,6             : Hexa-methylene diamine and adipic acid.

–     Nylon 6,10 : Hexa-methylene diamine and sebasic acid.

–     Nylon 11              : 11-Amino undecanoic acid.

–     Nylon 7                : Amino Heptanoic acid.

Physical properties:

Tenacity                         : 4-9 gm/den (dry), in wet 90% of dry.

Elasticity                        : Breaking extension — 20-40%.

Stiffness                         : 20-40 gm/den.

Moisture regain              : 3.5-5%

Specific gravity              : 1.14.

Abrasion resistance       : Excellent.

Dimensional stability     : Good.

Resiliency             : Excellent.

Softening point              : Nylon 6,6 — 229^oC, Nylon 6 — 149^oC.

Melting point                 : Nylon 6,6 — 252^oC, Nylon 6 — 215^oC.

Hand feel              : Soft and smooth.

Chemical properties:

Acid:

Nylon 6,6 is attacked by mineral acids is disintegrate or dissolve almost. But is

inert to dilute acetic acid and formic acids even of the boil. It is dissolved in

the concentrated formic acid. Nylon 6 is attacked by mineral acid but resistant

to dilute boiling organic acid.

Bleaches:

Not affected by oxidizing and reducing bleaches but may be harmed by

chlorine and strong oxidizing bleaches.

Alkali: Nylon is substantially inert to alkalis.

Organic solvent: Most organic solvent have little or no effect on nylon.  

Light: No discoloration. Nylon 6 gradually loss of strength on prolonged extension.

Biological: Neither micro organism nor moth, larvae attack nylon.

Electrical : High insulating properties leads to static charges on the fibre.

Flammability : Burns slowly.

Uses of Nylon

Apparel use:

 High tenacity nylons are used for parachute fabrics, cords and ropes. Having good

dimensional stability, nylons are used for ladies gloves, ladies hose, under wear,

swimming wear, hosiery fabric etc.

Domestic use:

 Nylon is used for home furnishing, in carpets, in upholstery and in ropes and

cords.

Industrial use:

 In fishing nets, tire cords, filtering cloths, sewing threads, tow ropes are made of

nylon. It is used in manufacturing of belts of various m/cs (Flat belt, V-belts).