How much does natural fiber know?

I. Introduction
Natural fibers are fibers with textile value that exist and grow in nature. The production of natural fibers throughout the world is large and growing, and it is an important source of materials for the textile industry.
Second, the structure
Natural fibers are textile fibers obtained directly from the natural or artificially cultivated plants and artificially raised animals, and are important sources of materials for the textile industry. Although the production of synthetic fibers has grown rapidly since the middle of the 20th century, natural fibers still account for about 50% of the total annual production of textile fibers.
The natural fibers found in nature include cotton, hemp, silk and animal hair. The molecular composition of cotton and hemp is mainly cellulose, while the molecular components of silk and wool are mainly proteins (exist in the form of a polyamide polymer).
The history of the use of natural fibers by humans can be traced back to ancient times. According to the history of science and technology in China, silk fabrics and hemp fabrics appeared in China from 4,000 to 5,000 years ago. Felts appeared 3,000 years ago and cotton fabrics appeared 2,000 years ago.
In the natural world, in addition to cotton and hemp, trees and grasses also grow large amounts of cellulose macromolecules. However, cellulose grown on trees and grasses does not exist in the state of long fibers and cannot be directly used as fibers. By chemically treating these natural cellulose macromolecules without changing their chemical structure, they merely change the physical structure of natural cellulose to produce cellulose fibres that can be used as fibres and have better performance. This technology is called artificial fibres. technology. Man-made fibers are one type of chemical fibers, and synthetic fibers are another type of chemical fibers. Man-made fibers are only one type of "glue" (known as rayon), and its chemical composition is a cellulose polymer.
Third, classification
There are many kinds of natural fibers, and there are four types of cotton, hemp, wool and silk that have been used in textiles for a long time. Cotton and hemp are plant fibers, and wool and silk are animal fibers. Asbestos is found in rock formations in the earth's crust, called mineral fibers. It is an important building material and can also be used in textile applications. The output of cotton fiber is the most, and its use is very wide. It can be used to sew clothes, bed sheets, bedding and other daily necessities, as well as materials for canvas and belts, or to make batting for insulation and filling materials. Most of the hemp fiber is used for the manufacture of packaging fabrics and ropes, and a portion of high quality hemp fiber is available for clothing. Wool and silk production is much less than cotton and linen, but it is an excellent textile raw material. It is made of wool fibers, made of satin silk fibers, and sewn to make garments. It is gorgeous and dignified and is loved by people. In textile fibers, only wool fibers have the properties of being pressed into felt. Hair fiber is also the best raw material for fiber carpets.
(a) Plant fiber
The main component is cellulose, also known as natural cellulose fibers. It is a fiber obtained from seeds, fruits, stems and leaves of plants. According to the site of growth on the plant, divided into seed fibers, leaf fibers and stem fibers.
1. Seed fiber: cotton, kapok, etc.;
2. Leaf fiber: sisal, abaca, etc.;
3. Stem fiber: ramie, flax, hemp, jute and so on.
(b) Animal fibers
The main component is protein, also known as natural protein fiber, divided into two categories, hair and glandular secretions.
1. Hair type: sheep wool, goat wool, camel hair, rabbit hair, yak hair, etc.;
2. Gland secretions: mulberry silk, tussah silk and so on.
(c) Man-made fibers
A textile fiber made by chemical processing, spinning and post-treatment using natural polymer materials such as cellulose and protein as raw materials. It is made of fiber raw materials that lose their value in textile processing and is dissolved or melted and redrawn. The original chemical structure remains unchanged, and the fiber components are still cellulose and proteins, respectively, and the resulting physical structure and chemical structure change are derived. The composition is cellulose acetate fiber.
1. Regenerated cellulose fiber: viscose fiber, rich fiber, cuprammonium fiber, etc.; (the difference is dissolved by different solutions of caustic soda and sulfur dioxide)
2. Cellulose ester fibers: Acetate fibers;
3. Regenerated protein fiber: Soybean fiber, peanut fiber, etc.
(D) Other fibers
synthetic fiber
Fibers obtained by spinning a raw material with an artificially synthesized polymer compound.
1. Ordinary synthetic fibers: polyester, nylon, acrylic, polypropylene, vinylon, and vinyllon;
2. Special synthetic fibers: aramid, spandex, carbon fiber, etc.
Inorganic fiber
Fiber made from mineral materials, such as: glass fiber, metal fiber, etc.
Mineral fiber
The main ingredients are inorganic, also known as natural inorganic fibers, inorganic metal silicates, such as asbestos fibers.
Chemical Fiber
Fibers made by chemical spinning using natural or synthetic polymer compounds as raw materials. Can be divided into man-made fibers, synthetic fibers, inorganic fibers.
Fourth, identify
Identification method:
1 The methods of identification are touch, visual inspection, combustion, microscopy, dissolution, drug coloring, and infrared spectroscopy. In the actual identification, often need to use a variety of methods, comprehensive analysis and research after the results.
2 The general procedure for identification is as follows:
A. First identify the natural fibers and chemical fibers by the combustion method.
B. In the case of natural fibers, microscopic observations are used to identify various plant fibers and animal fibers. If it is a chemical fiber, the difference in melting point, specific gravity, refractive index, and dissolution performance of the combined fiber is distinguished one by one.
C. In the identification of mixed fibers and blended yarns, it is generally confirmed by microscopic observation that several kinds of fibers are contained therein, and then identified one by one by an appropriate method.
D. For dyed or finished fibers, dye stripping or other appropriate pretreatments are generally required before reliable identification can be guaranteed.
Identification method:
1. Hand-feel visual method: This method is applicable to textile materials in the state of loose fibers.
(1) Cotton fibers are shorter and finer than ramie fibers and other hemp fibers, and often contain various impurities and defects.
(2) Hemp fiber feels rougher.
(3) Wool fibers are curled and elastic.
(4) Silk is a filament, long and slender, with a special luster.
(5) In chemical fibers, only viscose fibers have large differences in dry and wet strength.
(6) Spandex filament has a very large elasticity, and its length can be stretched to more than five times at room temperature.
2. Microscopic observation method: Fibers are identified based on the longitudinal and cross-sectional morphological characteristics of the fiber.
(1), cotton fiber: cross-sectional morphology: waist round, with a middle waist; vertical surface morphology: flat ribbon, a natural turn.
(2), hemp (ramie, flax, jute) fiber: cross-sectional morphology: waist round or polygonal, with a cavity; vertical surface morphology: a horizontal section, vertical stripes.
(3) Wool fibers: cross-sectional morphology: round or nearly circular, some with a long hairline; longitudinal surface morphology: scales on the surface.
(4), rabbit hair fiber: cross-sectional morphology: dumbbell-shaped, with a long hair; vertical surface morphology: scales on the surface.
(5), mulberry silk fiber: cross-sectional morphology: irregular triangle; vertical surface morphology: smooth and straight, longitudinal stripes.
(6) Ordinary viscose: cross-section morphology: zigzag, skin core structure; vertical surface morphology: longitudinal grooves.
(7) Rich and strong fiber: cross-sectional morphology: less toothed, or round, oval; vertical surface morphology: smooth surface.
(8) Acetate fiber: cross-sectional morphology: trilobal or irregular zigzag; longitudinal morphology: longitudinal stripes on the surface.
(9), Acrylic fiber: cross-sectional shape: round, dumbbell-shaped or leaf-shaped; vertical surface morphology: the surface is smooth or striped.
(10) Polychlorin fiber: cross-sectional morphology: nearly circular; longitudinal morphology: smooth surface.
(11), Spandex fiber: cross-sectional morphology: irregular shape, a round, potato-shaped; vertical surface morphology: the surface is dark, unclear bone-shaped stripes.
(12) Polyester, Polyamide, Polypropylene Fibers: Cross-sectional morphology: Round or profiled; Vertical morphology: Smooth.
(13), PVA fiber: cross-sectional morphology: waist round, skin core structure; vertical surface morphology: 1 to 2 grooves.
3, density gradient method: It is based on the characteristics of various fibers with different densities to identify fibers.
(1), set the density gradient fluid, the general use of xylene carbon tetrachloride system.
(2) Calibrating the density gradient tube. The precision ball method is commonly used.
(3) Measurement and calculation The fiber to be tested is subjected to deoiling, drying and defoaming pretreatment. After the ball is put into balance, the fiber density is measured according to the position of the fiber suspension.
4, fluorescence method: the use of ultraviolet fluorescent light irradiation fiber, according to the different nature of a variety of fiber light, the fiber's fluorescent color is also different characteristics to identify fibers. The fluorescent colors of various fibers specifically show:
(1), cotton, wool fiber: light yellow
(2) Mercerized cotton fiber: light red
(3), jute (raw) fiber: purple brown
(4), jute, silk, nylon fiber: light blue
(5), viscose fiber: white purple shade
(6), Viscose Viscose: Light Yellow Violet Shadow
(7) Polyester fiber: White light is bright
(8), vinylon has optical fiber: light yellowish purple shade.
5, the combustion method: According to the chemical composition of the fiber, the combustion characteristics are also different, so as to roughly distinguish the major categories of fiber. Comparison of the combustion characteristics of several common fibers is as follows:
(1) Cotton, hemp, viscose, cuprammonium fiber: close to the flame: not shrinking or melting; contact with the flame: rapid burning; leaving the flame: continuing to burn; odor: smell of burning paper; residue characteristics: a small amount of grayish black or grayish white ash.
(2), silk, wool fiber: close to the flame: curl and melt; contact flame: curl, melt, burn; leave the flame: slow combustion sometimes self extinguishing; odor: burning hair odor; residue characteristics: loose and brittle black particles Or coke-like.
(3) Polyester fiber: close to the flame: condense; contact the flame: melting, smoking, slow burning; leave the flame: continue to burn, sometimes self-extinguishing; odor: special aromatic sweetness; residue characteristics: hard black ball .
(4), nylon fiber: close to the flame: melting; contact flame: melting, smoking; leaving the flame: self-extinguishing; odor: amino taste; residue characteristics: hard pale brown transparent beads.
(5) Acrylic fiber: close to the flame: melting; contact with the flame: melting, smoking; leaving the flame: continue burning, black smoke; smell: spicy taste; residue characteristics: black irregular beads, fragile.
(6) Polypropylene fiber: close to the flame: fused; contact flame: melting, burning; leaving the flame: continuing to burn; odor: paraffin wax; residue characteristics: gray hard transparent beads.
(7) Spandex fiber: close to the flame: condense; contact the flame: melting, burning; leaving the flame: self-extinguishing; odor: specific taste; residue features: white gelatinous.
(8) Chlorophyll fiber: close to the flame: condense; contact flame: melting, burning, black smoke; leaving the flame: self extinguishing; odor: pungent odor; residue characteristics: dark brown lump.
(9), vinylon fiber: close to the flame: melting; contact flame: melting, burning; leaving the flame: continue burning, black smoke; odor: unique flavor; residue characteristics: irregular brown brown hard coke.
Fifth, application
Natural fibers are mainly used as clothing and various textiles. Viscose silk is mainly used as a substitute for part of cotton to make various fabrics and clothing. Viscose fiber can also be used as a raw material of carbon fiber to burn high-strength high-modulus carbon fiber. It can also spin cellulose solution into a "hollow" tubular fiber in the fiber-forming process for sewage treatment and drinking water purification. Technology (making drinking "mineral water") membrane separation material.
The natural fiber and man-made fiber industries are mainly in the textile field. Research and development of a variety of inexpensive textile products and apparel products suitable for market demand are one of the main goals of the textile industry. Natural fibers, as a polymer, are studied in terms of chemical modification and comprehensive utilization of macromolecular resources, which is another research topic of natural fiber resources.

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