Textile fiber overview
Fabric fiber is a soft, thin, long and spinnable substance. The ratio of length to diameter of fibers available for fabrics should generally be greater than 1000:1. As a fabric fiber, it should also have good physical and mechanical properties, such as certain strength, elasticity and relatively good chemical stability. Cotton, wool, silk and linen in nature are ideal natural fabric fibers. In addition, chemical fibers produced by chemical methods have occupied an important position in fabric fibers. They can be divided into two categories: regenerated fibers and synthetic fibers. Regenerated fiber includes regenerated cellulose fiber (viscose, cupro, Fuqiang, Tencel fiber, etc.), cellulose ester (acetate fiber), regenerated protein fiber (casein fiber, soy protein fiber, etc.). Synthetic fibers include nylon, polyester, polyacrylonitrile fiber, vinylon, polypropylene, chlorine fiber, spandex, etc. With the advancement of science and technology, the varieties of these fibers are constantly expanding, and scientific 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. Synthetic polymer compounds are named according to the names of the raw materials used, with the word “poly” in front. For example, polyacrylonitrile fiber is polymerized from 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 macromolecule and is connected in the form of a primary valence bond, the number of repetitions is called the degree of polymerization (expressed in terms of planes), such as the fibers that make up cotton fiber. The macromolecule can be simply expressed as (C6H1005)n. The n value is the degree of polymerization. Different polymer compounds have different degrees of polymerization, and the polymerization degrees of various fabric fibers are also different. For example, the DP of cotton fiber is 2500 to 10000, and the DP of viscose fiber is 250 to 500. Regardless of relative molecular mass or degree of polymerization, it can indicate the size of the molecular chain of a polymer compound and is one of the important indicators for identifying the degree of fiber damage.
The obvious difference between high molecular compounds and low molecular compounds is the relative molecular mass and the size of the intermolecular force caused by the macromolecules. The intermolecular forces of polymer compounds include van der Waals forces, hydrogen bonds, etc. These forces have a great impact on the deformation or breakage of fiber molecules, changes in elasticity, and the coloring properties of various dyes. Due to the different structures of the macromolecular main chains, polymer compounds have different physical and chemical properties, which are manifested in different properties such as strength, elasticity, elongation, acid resistance, alkali resistance, and resistance to oxidation and reduction. These different properties are very important for formulating dyeing, finishing and finishing products. Craftsmanship is very important. Polymer compounds have very long molecular chains and high intermolecular binding forces, so they are only in solid and liquid states, not gaseous. The macromolecules in solid polymer compounds have a certain geometric arrangement. Those in which the molecules are ordered and stacked are called crystalline states; those without lattice structures are called amorphous states, also known as amorphous structures. When coloring, dyes generally can only enter the amorphous zone or the edge of the crystallized zone. Excessive external force and excessive temperature can damage the crystal structure of the fiber macromolecular chain or cause crystal melting. Amorphous linear polymer compounds exhibit three states with temperature changes, namely glassy state, highly elastic state and viscous flow state, when the external force remains unchanged. The determination of these three states and two transition temperatures (T9 is the glassy state temperature and Tf is the viscous fluid state temperature) of polymer compounds is of useful significance to the sorting and application of polymers. For example, the T of nylon is 50°C. When dyeing, dyes can only be dyed if the temperature exceeds the Tg. Another example is that the Tf of polyester is about 240°C, so the setting temperature cannot exceed Tf. If it exceeds this temperature, the fiber will deform and cannot reply.
Various fabric fibers have certain appearance and cross-sectional shapes. For example, cotton fiber has a naturally curly appearance and a waist-shaped cross-section; the main body of silk is silk protein, which is surrounded by sericin; wool has a scale layer and cortex. layer. Nylon, polyester, polyacrylonitrile fiber, and vinylon are commonly known as the four major fibers. Their cross-sections are somewhat similar. For example, the cross-sections of nylon and polyester are almost circular; the cross-section of vinylon is kidney-shaped and has an obvious skin-core structure. These shapes It is of great help in identifying fabric fibers and developing new varieties of fabrics. In addition, fiber modification technology is also changing rapidly. Physical modifications such as special-shaped fibers, elastic fibers, loose fibers, etc.; chemical modifications such as cationization of cotton fibers, acid modification of polyester, organometallic compound modification of polypropylene, and plasma modification have greatly increased the number of new types of fibers. The varieties of fibers and the improved coloring properties of fibers have made people’s clothing and decorations more colorful.
In recent years, with the enhancement of environmental awareness, the research and development of biodegradable synthetic fibers has attracted sufficient attention. Biodegradable fiber is an environmentally friendly material that helps humans reduce environmental burdens and achieve a good balance between modern civilization and nature.
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