Nylon

Structure

Polyamide, commonly known as Nylon (Nylon), the English name Polyamide (PA for short), is the main chain of the molecule contains repeated amide groups -[NHCO]- thermoplastic resin general term, including aliphatic PA, aliphatic-aromatic PA and aromatic PA. PA varieties, large production, widely used, its name by the synthesis of monomer specific number of carbon atoms. It was invented by the famous American chemist Carothers and his scientific research group.

Molecular structure

Commonly used nylon fibers can be divided into two categories.

One category is polydiamine diamine dibasic acid obtained by polycondensation of diamine and dibasic acid, the chemical structure formula of its long chain molecule is:

H-[HN(CH2)xNHCO(CH2)yCO]-OH

The relative molecular weight of this type of nylon is generally 17,000-23,000.Depending on the number of carbon atoms of the diamine and the dibasic acid used, different nylon products can be obtained and can be differentiated by the number added to the nylon, where the first number is the number of carbon atoms of the diamine and the second number is the number of carbon atoms of the dibasic acid. For example, nylon 66, indicating that it is produced by the polycondensation of hexanediamine and adipic acid; nylon 610, indicating that it is produced by hexanediamine and sebacic acid.

Another class is obtained by polycondensation or ring-opening polymerization of lactams, whose long-chain molecules have the chemical structure formula:

H-[NH(CH2)xCO]-OH

According to the number of carbon atoms contained in its unit structure, different varieties of nomenclature can be obtained. Nylon 6, for example, indicates that it is obtained by ring-opening polymerization of caprolactam containing 6 carbon atoms.

Nylon 6, nylon 66 and other aliphatic nylons are composed of linear macromolecules with amide bonds (-NHCO-). Nylon molecules have -CO- and -NH- groups, which can form hydrogen bonds between or within molecules, and can also be combined with other molecules, so that nylon has a better hygroscopic capacity and can form a better crystalline structure.

Nylon molecules -CH2- (methylidene) between because can only produce a weak van der Waals force, so -CH2 - chain section of the molecular chain part of the curvature of the larger. Various nylon due to the different number of -CH2-, so that the intermolecular hydrogen bonding form is not exactly the same, while the probability of molecular curling is not the same. In addition, some nylon molecules have directionality. The orientation of the molecules is different, the structural properties of the fiber are not exactly the same.