Poly amide Fiber Chemical Composition
Published on: Mar 4, 2016
Transcripts - Polyamide
Polyamide substance composed of long, multiple-unit molecules in which the
repeating units in the molecular chain are linked together by amide groups.
Amide groups have the general chemical formula CO-NH. They may be produced
by the interaction of an amine (NH2) group and a carboxyl (COOH) group.
When 85% or more of the amide groups are linked directly to phenyl rings, the
polyamide is classified as an aramid. When the rate is lower than 85%, the polymer
is classified as a nylon.
Commonly Used Polyamide:
Large number of polyamide materials available to produce nylon fibers.
The two most common versions are
Nylon 66 (polyhexamethylene diamide)
Nylon 6 (Polycaprolactam)
Chemical Composition of Nylon 6:
Nylon6 is made from Caprolactum which is made by a series of reactions using
products obtained from coal tar.
Coal Tar--> Benzene--Chlorine--> Chlorobenzene--> Sodium Phenate--HCL-->
Phenol--H2 (Nickel)-->Cyclohexanol--Oxidation Air Fe, Zn Catalyst--> Cyclohexanone-
-> Cyclohexanone Oxime--H2SO4--> Caprolactam
I am including it to show that it is possible to get a polyamide from a single monomer.
Caprolectum is a white flaky solid, melting at 68 degree and is soluble in
water. the polymerization is carried out in stainless steel cylinders.
Caprolactam has 6 carbon Hence “Nylon 6”. When Caprolactam is heated at
533k(500oC) in presence of nitrogen for 4-5 hours . The ring breaks and under goes
Amide Bond within each Caprolactam molecule broken .The ring opens, and the
molecules join up in a continuous chain
Polymerization of Nylon 6:
Melt Spinning of Nylon 6:
Chemical Properties of Nylon 6:
Acids - concentrated Poor
Acids - dilute Poor
Aromatic hydrocarbons Good
Greases and Oils Good
Halogenated Hydrocarbons Good-Poor
Physical Properties of Nylon 6:
Density ( g cm-3
Limiting oxygen index ( % ) 25
Radiation resistance Fair
Refractive index 1.53
Resistance to Ultra-violet Poor
Water absorption - equilibrium ( % ) >8
Water absorption - over 24 hours ( % ) 2.7
Nylon 6,6 is made of hexamethylenediamine and adipic acid, which give nylon 6,6 a
total of 12 carbon atoms, and its name Nylon 66
Hexamethylene diamine and adipic acid are combined with water in a reactor. This
produces nylon salt. The nylon salt is then sent to an evaporator where excess water
is removed. The nylon salt goes into a reaction vessel where a continuous
polymerization process takes place.
Chemical Composition of Nylon 66:
One of the monomers is a 6 carbon acid with a -COOH group at each end - hexanedioic acid.
The other monomer is a 6 carbon chain with an amino group, -NH2, at each end. This is 1,6-
When these two compounds polymerise, the amine and acid groups combine, each time with
the loss of a molecule of water. This is known as condensation polymerisation.
Condensation polymerisation is the formation of a polymer involving the loss of a small
molecule. In this case, the molecule is water,
keeps on happening, and so you get a chain which looks like this:
Polymerization of Nylon 66:
Melt Spinning of Nylon 66:
Chemical Properties of Nylon
Material Medium High tenacity
Density g cm-3
Extension to break % 37 14-22
Shrinkage @100C % 9 9-11
Specific Tenacity cN/tex 43 60-80
Uses of Nylons:
Synthetic replacement for silk
It replaced silk in military applications such as parachutes and flak
vests, and was used in many types of vehicle tires.
Used in many applications, including fabrics, bridal veils, carpets,
musical strings, and rope.
Ropes Zip ties