Polyamide

A polyamide is a polymer whose chains contain repeating amide linkages. The class includes natural materials such as proteins and synthetic materials such as nylon.

Amide: An amide is a compound containing a carbonyl group bonded to nitrogen. The amide linkage is the defining repeating unit in a polyamide chain.
Nylon 6: Nylon 6 is a synthetic polyamide made by ring-opening polymerization of caprolactam. It is a widely used example of a polyamide made from one principal monomer.
Nylon: Nylon is a family of synthetic polyamides used in fibers, films, and molded products. Nylon is the best-known synthetic polyamide family and spans textile and engineering uses.
Polyester: A polyester is a polymer whose backbone contains repeating ester linkages. Polyesters offer a useful comparison because their backbone linkage differs from the amide bond.
Condensation polymerization: Condensation polymerization joins molecules while releasing small molecules such as water or methanol. Many polyamides form when monomers create amide bonds while eliminating small molecules.
Nylon 6,6: Nylon 6,6 is a synthetic polyamide produced from hexamethylenediamine and adipic acid. Its alternating diamine and diacid-derived units illustrate a common polyamide chain architecture.
Aramid: An aramid is an aromatic polyamide whose chain contains aromatic rings directly connected to amide groups. Aramids use polyamide chemistry to achieve high strength and heat resistance.
Polyurethane: A polyurethane is a polymer containing urethane linkages formed from isocyanates and polyols. Polyurethanes also contain nitrogen-bearing linkages but have different chemistry and property ranges.
Step-growth polymerization: Step-growth polymerization builds polymers through reactions between functional groups on molecules of any chain length. This polymerization pattern allows polyamide chains to grow through repeated reactions between amine and acid-derived groups.
Crystallinity: Crystallinity is the degree to which a solid's molecules form ordered structures. Polyamide crystallinity affects stiffness, strength, heat resistance, and dimensional stability.

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