The frictional properties of fibers can determine the ease of sliding between fibers, so it plays an important role in the mechanical processing of fibers such as carding, spinning or winding. Synthetic fibers such as amide fiber, polyester fiber, acrylonitrile fiber and other polymer compounds have high strength, small shrinkage, no mold, no decay, wear resistance, but poor water absorption, air permeability, easy to fuzziness, large friction during processing, easy to produce electrostatic accumulation, dyeing is more difficult, so it is necessary to add fabric softener during processing to reduce friction and increase its smoothness, improve its spinnability. The so-called softener is an auxiliary agent that can adjust the friction resistance between the fabric fiber tissues or between the fiber and the body, so that the fiber has a good elasticity and a soft and smooth feeling. These softeners are chemically and physically adsorbed on the fabric to form a lipophilic film or produce positive electricity. Due to the formation of its lipophilic film, it can significantly reduce the static friction coefficient of the fiber surface, reduce the accumulation of static electricity and improve the interaction between fibers, so that the micro-fibers lie parallel to the fiber bundle, eliminating the "backwinding", and by covering and lubricating the fiber bundle, reduce the friction between the fibers, and get a softer and more flexible fiber.
According to the use of softener can be divided into textile industry softener, oil and home softener. According to their ionic properties, industrial softeners can be divided into anionic, non-ionic, cationic and zwitterionic four categories. Cationic and zwitterionic softeners with good effect are commonly used, and almost all of them are quaternary ammonium salts, which have been widely used in the soft treatment of cotton and synthetic fiber fabrics. The cationic softener molecule contains one or two stearic acid chains or hydrogenated taloic acid chains, and the softness of two fat chains is better.