Views:5 Author:Site Editor Publish Time: 2020-04-07 Origin:Site
1. The main variety of nylon is aliphatic polyamide fiber, which can be synthesized with a single monomer, such as lactam or amino acid. At this time, the Arabic number after the nylon name indicates the number of carbon atoms of the lactam or amino acid used, such as nylon 6, nylon 11, etc .; it can also be synthesized with two monomers, namely a diamine and a dibasic acid. At this time, in the two groups of Arabic numerals after the nylon name, the first group represents the number of carbon atoms of the diamine, and the second group represents the number of carbon atoms of the dibasic acid, such as nylon 66, nylon 610, nylon 1010, etc.
Generally speaking, the feel of nylon 66 is better than that of nylon 6, and the comfort of nylon 66 is also better than that of nylon 6, but it is difficult to distinguish nylon 6 and nylon 66 from the surface.
Nylon 6 products have the characteristics of high strength, wear resistance, softness and mild skin touch, and have a wide range of applications in the fields of clothing, silk, umbrellas, fishnet yarns, cords, BCF carpet yarns, and engineering plastics.
2. The degree of polymerization of nylon 6 is 140-200, and the degree of polymerization of nylon 66 is 55-77.
The molecular chain of nylon contains a large number of amide groups, which can form attractive hydrogen bonds with the amide groups of adjacent molecular chains. The chain segment CH2-CH2- has excellent flexibility, and the molecular chain structure is relatively regular. Large side groups, easy to form crystals when the molecular chain stretches, its crystallinity is 50% to 60%. Nylon is made by melt spinning. The shape under the microscope is similar to that of polyester. The cross-section is round and the longitudinal direction is smooth and straight. The density is small, about 1.14g / cm3.
(1) The main properties of nylon
1. Hygroscopicity and dyeability Nylon has good hygroscopicity, and the moisture regain rate under standard atmospheric conditions is about 4.5%. The dyeing performance is good, and it can be dyed with disperse dyes, acid dyes, and other dyes.
2. Mechanical properties The strength of nylon is the highest among synthetic fibers, and it has good resilience. The elastic recovery rate at 10% elongation is over 90%. The initial modulus is low, and it is easy to deform under a small load. It has the best resistance to embarrassment, about 10 times that of cotton, 20 times that of wool, and 140 times that of viscose fiber when wet.
3. Thermal properties The glass transition temperature of nylon is relatively low, 45 ～ 60 ℃, the melting point of nylon 6 is 210 ～ 215 ℃, the decomposition point is 300 ℃, and the melting point of nylon 66 is 255 ℃. Nylon has poor heat resistance and shrinks when exposed to heat. The shrinkage of boiling water is as high as 11.5%. If kept at 150 ℃ for 50 hours, the fiber will turn yellow and lose its value.
4. Chemical properties Nylon is resistant to alkalis and acids, treated with 10% caustic soda solution at 95 ° C for 16h, and the strength is not lost. It will dissolve in various concentrated acids, 59% sulfuric acid and hot formic acid, acetic acid can dissolve nylon, 15% and 20% hydrochloric acid can dissolve nylon 6 and nylon 66, respectively.
5. Optical properties Nylon has poor light resistance. It will turn yellow and become brittle when exposed to sunlight for a long time.
(2) Use of nylon
Nylon is mainly composed of filaments, and a small amount of short fibers are mainly used for blending with wool, cotton or other chemical fibers. The purpose is to improve the strength and wear resistance of the fabric. Part of the nylon filament is used in silk, scarves, lace, etc., most of it is processed into stretch silk, and the socks, nylon shirts, gloves, etc. made of it are strong and durable. Industrial nylon accounts for more than 40%. Due to its high strength, fatigue resistance, impact resistance, and good affinity with rubber, it is suitable for making tire cords for trucks, airplanes, and other tires. 4 to 5 times longer. Besides, it is also used for cables, parachutes, ladders, conveyor belts and nylon ropes.