Repeating units connected by amide bonds form a macromolecule known as Polyamide. Polyamides are both natural as well as synthetic.
Mostly polyamides are formed either by the reaction of ring-opening polymerization of lactams with a diacid or reaction of the diacid with a diamine y. Polyamides are either all aliphatic or all aromatic. The aromatic polyamides have superior strength, enhanced solvent, fire and warmth resistance with greater dimensional constancy than the all aliphatic amides for example (Nylon). The aromatic polyamides are also called aramids but are much more exclusive and more difficult to create.
The aliphatic polyamides being the most significant group of engineering thermoplastics are produced on a large amount. They are shapeless or only fairly crystalline when injection molded. The two major significant polyamides are (Nylon 6, 6) and polycaprolactam (Nylon 6) and poly (hexamethylene adipamide). Both have outstanding mechanical properties including high tensile power, superior flexibility.
The Polyamide characteristics offer a whole range of benefits:
- Balanced robustness and inflexibility
- Good automatic strength
- High collision strength
- Good moist characteristics
- Good scratch and wear resistance.
- High power and shock absorption
- No breakable fractures under pressure or collision loads
- Good sliding properties
- Extremely high impact strength
- No brittle fractures
Polyamides have more than a few advantages over other classes of polymers. For example, they are not as resistant to acid hydrolysis and are more resistant to alkaline hydrolysis as compared to polyesters. The polyamide-epoxy thermoset blends are extremely adhesive; partly due to the elevated concentration of polar groups. Most of the properties of polyamides differ from the tough and hard PA 66 to the soft and supple PA 12. Depending on the kind, polyamides absorb diverse amounts of wetness, which somehow affects the mechanical characteristics as well as the dimensional correctness.
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