Commonly used nylon fibers can be divided into two categories.
One type is polyhexamethylene adipate which is obtained by polycondensation of a diamine and a diacid. The chemical structure of the long-chain molecule is:
H—[HN(CH2)XNHCO(CH2)YCO]—OH
The relative molecular weight of such nylons is generally from 17,000 to 23,000. Depending on the number of carbon atoms of the diamine and dibasic acid used, different nylon products can be obtained and can be distinguished by the number added after the nylon, wherein the former number is The number of carbon atoms of the diamine, the latter number being the number of carbon atoms of the dibasic acid. For example, nylon 66, which is obtained by polycondensation of hexamethylenediamine and adipic acid; nylon 610, which is derived from hexamethylenediamine and sebacic acid.
The other type is obtained by polycondensation or ring-opening polymerization of caprolactam, and the chemical structure of the long-chain molecule is:
H—[NH(CH2)XCO]—OH
According to the number of carbon atoms contained in the unit structure, the naming of different varieties can be obtained. For example, nylon 6, indicating that it is obtained by ring-opening polymerization of caprolactam having 6 carbon atoms.
Nylon 6: Nylon 66 and other aliphatic nylons are composed of linear macromolecules with an amide bond (—NHCO—). The nylon molecules have -CO-, -NH- groups, which can form hydrogen bonds in the intermolecular or intramolecular groups, and can also be combined with other molecules, so the nylon has better moisture absorption capacity and can form a better crystal structure. The -CH2-(methylene) in the nylon molecule can only produce a weak van der Waals force, so the molecular chain of the -CH2-segment portion has a large degree of curl. The variety of various nylons, CH2, is different, so that the binding forms of intermolecular hydrogen bonds are not exactly the same, and the probability of molecular curling is also different. In addition, some nylon molecules are also directional. The directionality of the molecules is different, and the structural properties of the fibers are not identical.
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