Natural fiber is a kind of textile fiber existing and growing in nature. The world's natural fiber production is large and growing, is an important source of materials for the textile industry.
2. The structure
Natural fiber is a kind of textile fiber directly obtained from natural plants or artificially cultivated animals, and is an important source of materials for textile industry. Although the output of synthetic fibers has increased rapidly since the middle of the 20th century, natural fibers still account for about 50% of the total annual output of textile fibers.
Natural fibers are mainly cotton, hemp, silk and animal hair. Among them, the molecular components of cotton and hemp are mainly cellulose, while the molecular components of silk and wool are mainly protein (in the form of polyamide macromolecule).
The history of using natural fiber can be traced back to ancient times. According to the records of the history of science and technology in China, silk and hemp fabrics appeared in China between 4000 and 5000 years ago, wool fabrics appeared 3000 years ago, and cotton fabrics appeared 2000 years ago.
The natural world in addition to cotton, hemp, trees, grass is also a large number of growth of cellulose polymer, but trees, grass growth of cellulose, is not a long fiber state, can not be used as a direct fiber. These natural cellulose polymer after chemical treatment, do not change its chemical structure, only change the physical structure of natural cellulose, so as to create can be used as fiber and better performance of cellulose fiber, this technology is called artificial fiber technology. Synthetic fibers are one kind of chemical fibers and synthetic fibers are another kind of chemical fibers. There is only one kind of man-made fiber, viscose silk (called rayon), whose chemical composition is cellulose polymer.
There are many kinds of natural fibers, which are widely used in the textile industry, including cotton, linen, wool and silk. Cotton and hemp are plant fibers, and wool and silk are animal fibers. Asbestos, which is found in rock formations in the earth's crust, is an important building material and can also be used for textile purposes. Cotton fiber output is the most, the use is very wide, can be used for sewing clothes, bed sheets, bedding and other daily necessities, can also be used as canvas and conveyor materials, or made into batt for insulation and filling materials. Hemp fiber is mostly used to make packing fabrics and ropes, and some of the fine hemp fiber can be used as clothing. Wool and silk yield much less than cotton and linen, but are excellent textile materials. Made of wool fiber woollen, made of silk fiber satin, sewing for clothing, gorgeous and solemn, loved by the people. In textile fibers, only wool fibers have the properties of being felted. Wool fiber is also the best raw material for fiber carpets.
(1) Natural fiber
The main constituent material is cellulose, also known as natural cellulose fiber. A fiber obtained from the seed, fruit, stem, leaf, etc of a plant. It can be divided into seed fiber, leaf fiber and stem fiber according to the different parts growing on the plant.
Seed fiber: cotton, kapok, etc.
Leaf fiber: sisal hemp, banana hemp, etc.
Stem fiber: ramie, flax, hemp, jute and so on.
(2) Animal fibers
The main component material is protein, also known as natural protein fiber, divided into hair and glandular secretion two categories.
Hair: sheep hair, goat hair, camel hair, rabbit hair, yak hair, etc.
Gland secretion: mulberry silk, tussah silk, etc.
(3) man-made fibers
Textile fiber made of cellulose, protein and other natural macromolecular materials through chemical processing, spinning and post-processing. Made of fiber raw materials that have lost the value of textile processing by artificial dissolution or melting and then silk drawing, the original chemical structure remains unchanged, and the fiber composition is still cellulose and protein respectively, and the derivative of the physical structure and chemical structure change formed is cellulose acetate fiber.
Regenerated cellulose fiber: viscose fiber, fuqiang fiber, copper ammonia fiber, etc. (the difference is dissolved in different solutions of caustic soda and sulfur dioxide)
Cellulose ester fiber: acetate fiber;
Regenerated protein fiber: soybean fiber, peanut fiber, etc.
(4) other fibers
A fiber made by spinning from a synthetic polymer.
Common synthetic fibers: polyester, polyamide, acrylic, polypropylene, polyvinylon, chloroprene, etc.
Special synthetic fiber: aramid fiber, spandex, carbon fiber, etc.
Fiber made from mineral materials, such as glass fiber, metal fiber, etc.
The main component is inorganic, also known as natural inorganic fiber, inorganic metal silicates, such as asbestos fiber.
A fiber made by chemical spinning from natural or synthetic macromolecular compounds. Can be divided into artificial fiber, synthetic fiber, inorganic fiber.
1. Identification methods include hand feeling, visual measurement, combustion, microscope, dissolution, drug staining and infrared spectroscopy. In the actual identification, often need to use a variety of methods, comprehensive analysis and research results.
2. General identification procedures are as follows:
First, natural and chemical fibers were identified by combustion.
In the case of natural fibers, microscopic observations are used to identify various plant and animal fibers. In the case of chemical fibers, differences in melting point, specific gravity, refractive index and solubility of the fibers are identified one by one.
In the identification of mixed fibers and blended yarns, it is generally possible to identify several fibers by microscopic observation, and then identify them one by one with appropriate methods.
For dyed or finished fibers, it is generally necessary to carry out dyeing stripping or other appropriate pretreatment before the reliable identification results can be guaranteed.
Classification of identification methods:
1. Hand-feel visual measurement: this method is applicable to textile raw materials in the state of loose fibers.
Cotton fiber than ramie fiber and other hemp process fiber, wool fiber are short and fine, often with a variety of impurities and defects.
Hemp fiber feels rough and stiff.
Wool fibers are curly and elastic.
Silk is filament, long and fine, with special luster.
The strength of viscose fiber in wet and dry state is the only chemical fiber.
Spandex is so elastic that it can stretch to more than five times its length at room temperature.
2. Microscopic observation: the fiber is identified according to its longitudinal and sectional morphological features.
Cotton fiber: cross section shape: waist round, with middle waist; Longitudinal plane configuration: flat zonal, have natural turn curve.
Hemp (ramie, flax, jute) fiber: cross section shape: waist round or polygonal, with a cavity; Longitudinal plane configuration: have horizontal section, vertical grain.
Wool fiber: cross section shape: round or nearly round, some with pith; Longitudinal form: scaly surface.
Rabbit hair fiber: cross section shape: dumbbell, pith hair; Longitudinal form: scaly surface.
Shape: irregular triangle; Longitudinal shape: smooth and straight, with longitudinal stripes.
Common viscose fiber: cross-section shape: zigzag, leather core structure; Longitudinal configuration: longitudinal grooves.
Fuqiang fibers: cross-sectional morphology: less toothed, or round, oval; Longitudinal shape: smooth surface.
Acetate fibers: cross-sectional shape: trifoliate or irregularly serrated; Longitudinal pattern: the surface has longitudinal stripes.
Acrylic fiber: cross section shape: round, dumbbell shape or leaf-like; Longitudinal shape: smooth or striated surface.
Shape of cross section: nearly round; Longitudinal shape: smooth surface.
Spandex fiber: cross section shape: irregular shape, round, potato shape; Longitudinal shape: dark surface, not clear bone stripe.
Polyester, nylon, polypropylene fiber: cross section shape: round or shaped; Longitudinal shape: smooth.
Vinylon fiber: cross section shape: waist round, leather core structure; Longitudinal configuration: 1~2 grooves.
3. Density gradient method: it is used to identify various fibers according to their different density characteristics.
The system of xylene tetrachloride is usually used to prepare density gradient liquid.
Precision pellet method is commonly used to calibrate density gradient tubes.
After measuring and calculating, the fiber to be measured was pretreated with deoiling, drying and defoaming, and made into pellets to be put into balance, and the fiber density was measured according to the fiber suspension position.
4. Fluorescence method: the fiber is irradiated by the ultraviolet fluorescent lamp. According to the different properties of various fibers, the fluorescence color of the fiber is also different to identify the fiber. Fluorescence color of various fibers:
Cotton and wool fiber: light yellow
Mercerized cotton fiber: light red
Jute (raw) fiber: purple-brown
Jute, silk, nylon fiber: light blue
Viscose: white and purple shades
Light viscose: yellowish - violet shade
Polyester fiber: white light blue sky light very bright
Vinylon fiber of light: yellowish violet shade.
5. Combustion method: according to the chemical composition of the fiber, the combustion characteristics are different, so as to roughly distinguish the major categories of the fiber. The combustion characteristics of several common fibers are compared as follows:
Cotton, hemp, viscose fiber, copper ammonia fiber: close to the flame: not shrink not melt; Contact flame: rapid combustion; Away from the flame: to continue burning; Smell: the smell of burning paper; Residue characteristics: small amount of grayish black or grayish white ashes.
Silk and wool fibers: close to the flame: curled and melted; Contact flame: curling, melting, burning; Leaving the flame: slow burning sometimes goes out on its own; Smell: the smell of burnt hair; Residue characteristics: loose and brittle black particles or coke like.
Polyester fiber: near the flame: shrinkage; Contact flame: melting, smoking, slow burning; Leave the flame: continue to burn, sometimes extinguished; Odor: special aromatic sweet taste; Residue features: hard black orb.
Nylon fiber: near the flame: melting; Contact flame: melting, smoking; Leaving the flame: self-extinguishing; Odor: amino taste; Residue characteristics: hard pale brown transparent beads.
Acrylic fiber: near the flame: melting; Contact flame: melting, smoking; Leave the flame: to continue burning, emitting black smoke; Smells: spicy; Residue characteristics: black irregular beads, fragile.
Polypropylene fiber: near the flame: melting; Contact flame: melting, burning; Away from the flame: to continue burning; Smells: paraffin; Residue features: pale hard transparent beads.
Spandex fiber: near the flame: melting; Contact flame: melting, burning; Leaving the flame: self-extinguishing; Odor: peculiar smell; Residue characteristics: white colloid.
PVC fiber: near the flame: melting; Contact flame: melting, burning, emitting black smoke; To extinguish by itself; extinguish. Odor: pungent odor; Residue characteristics: dark brown lumps.
Vinylon fiber: near the flame: melting; Contact flame: melting, burning; Leave the flame: to continue burning, emitting black smoke; Odor: characteristic fragrance; Residue characteristics: irregular burnt tan - colored lump.
5. the application
Natural fibers are mainly used in clothing and various textiles. Viscose silk is mainly used to replace part of cotton, do a variety of fabrics and clothing. Viscose silk fiber can also be used as raw material for carbon fiber to make high-strength and high-modulus carbon fiber. In addition, cellulose solution can be spun into "hollow" tubular fiber during the fiber forming process, which can be used as membrane separation material in sewage treatment and drinking water purification technology (making drinking water "mineral water").
The natural fiber and artificial fiber industry is mainly engaged in the textile field. It is one of the main goals of the textile industry to develop various kinds of inexpensive textile products and clothing products suitable for the market demand. Natural fiber as a polymer, the study of its chemical modification and comprehensive utilization of polymer resources, natural fiber resources is another research topic.
Source: new media for cotton textile technology