Introduction to the molecular structure of nylon in Nylon High Elastic Yarn

Nylon High Elastic Yarn is a high elastic yarn made of nylon as the main raw material. Nylon is a synthetic polymer. The molecular structure of nylon determines its mechanical properties, elasticity and wide application in the textile industry. The following will introduce in detail what the molecular structure of nylon in nylon high elastic yarn is, and how this structure gives nylon high elastic yarn good elasticity and other good properties.

1. Nylon belongs to the polyamide compound. Its basic structural unit is the amide bond (-CONH-), which is formed by the reaction of carboxylic acid and amine. The molecular chain of nylon is a long-chain polymer connected by repeated amide groups, and each monomer unit usually contains 6 to 12 carbon atoms. According to the number of carbon atoms, nylon can be divided into different types, such as nylon 6, nylon 66, etc.
Take nylon 66 as an example. It is polymerized by adipic acid (a diacid containing six carbon atoms) and hexamethylenediamine (a diamine containing six carbon atoms). Its chemical formula can be expressed as (-[CO-(CH2)4-CO-NH-(CH2)6-NH]-)n, where n represents the degree of polymerization, that is, the number of repeating units in the molecular chain. The amide groups formed by hydrogen bonds in the nylon 66 molecular chain are arranged closely, forming highly ordered crystalline regions and relatively disordered amorphous regions.

2. There are crystalline regions and amorphous regions in the molecular structure of nylon, both of which have an important influence on the physical properties of nylon.
Crystalline region: Crystalline region refers to the region where nylon molecular chains are arranged in a highly ordered manner. These regions have high density and strength, providing the main mechanical properties of nylon materials. Because the molecular chains are closely arranged in the crystalline region and the hydrogen bonding effect is strong, this region has high tensile strength and wear resistance.
Amorphous region: Amorphous region refers to the part where the molecular chains are arranged relatively loosely and disorderly. Compared with the crystalline region, the molecular chains in the amorphous region have greater freedom of movement. These regions give nylon materials a certain degree of flexibility and elasticity, which can deform when subjected to external force and quickly return to their original shape after the external force is removed.

3. The molecular chain structure of nylon has significant flexibility, which is the key to the elasticity of nylon high elastic yarn. Nylon's molecular chain is long and consists of multiple repeating units. Each unit is connected by amide bonds. The molecular segments between these amide bonds can rotate and bend freely, allowing the entire molecular chain to stretch and shrink under the action of external forces.
When nylon high elastic yarn is stretched, the molecular segments in the amorphous region will deform first, and these molecular segments will stretch along the stretching direction. However, due to the existence of the crystalline region, the molecular chain will not be stretched indefinitely. When the external force is removed, the action of hydrogen bonds allows the molecular segments to quickly retract to their original positions, thereby showing the good elastic recovery of nylon high elastic yarn.

4. Nylon molecular chains interact with each other through hydrogen bonds, which are caused by the difference in electronegativity between nitrogen atoms and oxygen atoms in the amide group. These hydrogen bonds not only increase the interaction between molecular chains, but also make nylon materials have a higher melting point and good heat resistance.
In nylon high elastic yarn, the presence of hydrogen bonds is a key factor in ensuring its elasticity and strength. When external force acts on the fiber, hydrogen bonds can provide additional resistance to prevent excessive movement of molecular chains. When the external force is removed, these hydrogen bonds will help the molecular chains return to their original arrangement, thereby maintaining the elasticity of the yarn.