Cloth fiber is a soft, thin and long material with spinnability. For fabrics, the ratio of length to diameter should generally be greater than 1000:1. As a fabric fiber, it should also have good physical and mechanical properties, such as definite strength, elasticity and better chemical stability. In nature, cotton, wool, silk, and linen are ideal natural fabric fibers. In addition, chemical fibers manufactured by chemical methods have occupied an important position in fabric fibers. They can be divided into two categories: renewable fibers and synthetic fibers. Regenerated fiber includes regenerated cellulose fiber (viscose, cupra, rich strength, Tencel fiber, etc.), cellulose ester (acetate fiber), and regenerated protein fiber (casein fiber, soybean protein fiber, etc.). Synthetic fibers include nylon, polyester, polyacrylonitrile, vinylon, polypropylene, chlorine, spandex, etc. With the advancement of science and technology, the varieties of these fibers are constantly expanding, and researchers are developing new types of regenerated fibers and synthetic fibers.
The basic components of all fabric fibers are polymer compounds, including natural polymer compounds (cellulose, protein) and synthetic polymer compounds. The synthetic polymer compounds are named according to the names of the raw materials used, and the word "poly" is added in front. For example, polyacrylonitrile fiber is polymerized with acrylonitrile as raw material. The relative molecular mass of polymer compounds is very large, generally between 104 and 107. Since the basic composition of a polymer compound is the repetition of a certain unit of its macromolecules and is connected in the form of main valence bonds, the number of repetitions is called the degree of polymerization (in terms of surface), such as the fibers that make up cotton fibers. Macromolecules can be simply expressed as (C6H1005)n. n is the degree of polymerization. Different polymer compounds have different degrees of polymerization, and the degree of polymerization of various fabric fibers is also different. For example, the DP of cotton fiber is 2500～10000, and the DP of viscose fiber is 250～500. Regardless of the relative molecular mass or degree of polymerization, it can indicate the size of the molecular chain of a polymer compound, which is one of the important indicators for identifying the degree of fiber damage.
All kinds of fabric fibers have certain appearance and cross-sectional shapes. For example, the appearance of cotton fiber is naturally crimped, and the cross-section is waist-shaped; the main body of silk is silk, which is surrounded by sericin; wool has scale layers and cortical layers. Polyamide, polyester, polyacrylonitrile, and vinylon are commonly known as the four major fibers. Their cross-sections are similar. For example, the cross-sections of nylon and polyester are almost round; the cross-section of vinylon is waist-shaped with a clear skin-core structure. It has great assistance in identifying fabric fibers and publishing new varieties of materials. In addition, fiber modification technology is also changing day by day. Physical modification, such as making special-shaped fibers, elastic fibers, loose fibers, etc.; chemical modification, such as cationization of cotton fiber, acid modification of polyester, modification of organometallic compounds of polypropylene, and plasma modification, etc., have greatly increased the new The variety of fiber and the improved coloring performance of fiber make people's clothing and decoration more colorful.