Polyamide, also known as PA, is a general term for thermoplastic resins with a recurring amide group–[NHCO]–on the molecular main chain. It is commonly referred to as nylon or nylon fiber. It includes aliphatic PA, aliphatic-aromatic PA, and aromatic PA. Among them, aliphatic PA has a wide variety, high production volume, and extensive applications. The naming of aliphatic PA is determined by the specific number of carbon atoms in the synthetic monomer. It was invented by the renowned American chemist Carothers and his research team. When used as a plastic, it is called nylon, and when used as a fiber, it is called nylon fiber, which can be made into long fibers or short fibers.
