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Polyamide
Polyamide fibers are composed of long molecular chains containing repeating amide groups. The two most common polyamides used to produce nylon fibers are nylon 6, which is made from caprolactam, and nylon 6,6, which is made from adipic acid and hexamethylenediamine. Nylon 6 is produced by polymerizing caprolactam, a white solid made from coal tar derivatives, above 500°C. Nylon 6,6 is formed through condensation polymerization of adipic acid and hexamethylenediamine with the loss of water. Both nylons are melt spun into fibers and widely used in applications such as fabrics, carpets, ropes and tires
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Polyamide
- 3. Polyamide Fibers: Polyamidesubstance 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. NH2+COOH CONH+H20 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. Amide Linkage
- 4. 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)
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- 6. Chemical Composition ofNylon 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. called caprolactam. Caprolectum is a white flaky solid, melting at 68 degree and is soluble in water. the polymerization is carried out in stainless steel cylinders.
- 7. Caprolactam has6 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 polymerization. Amide Bond within each Caprolactam molecule broken .The ring opens, and the molecules join up in a continuous chain Polymerization of Nylon 6: Step Growth 6 Carbons
- 8. Melt Spinning ofNylon 6:
- 9. Chemical Properties ofNylon 6: Acids - concentrated Poor Acids - dilute Poor Alcohols Good Alkalis Good-Fair Aromatic hydrocarbons Good Greases and Oils Good Halogenated Hydrocarbons Good-Poor Halogens Poor Ketones Good
- 10. Physical Properties ofNylon 6: Density ( g cm-3 ) 1.13 Flammability HB 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
- 11. Nylon 6,6is 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:
- 12. One ofthe 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- diaminohexane. 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:
- 13. Melt Spinning ofNylon 66:
- 14. Chemical Properties ofNylon 66: Property Value Material Medium High tenacity Density g cm-3 1.14 1.14 Extension to break % 37 14-22 Shrinkage @100C % 9 9-11 Specific Tenacity cN/tex 43 60-80
- 15. 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.
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