Fiber

The term fiber (or fibre) is used for a class of materials that consist of continuous filaments or are in discrete elongated pieces, similar to lengths of thread. Fibers are of great importance in the biology of both plants and animals, for holding tissues together. Humans use natural and synthetic fibers for diverse purposes. For instance, some fibers are spun into filaments, thread, string or rope. Some are components of composite materials, others are matted into sheets for products such as paper or felt.

Natural fibers

Natural fibers include those derived from plant, animal, and mineral sources. Examples of natural fibers and their sources are given below.

Plant fibers

Plant fibers may be derived from fiber crops (such as cotton), trees, straw, bamboo, and sugarcane. Their main constituent is cellulose, which may also contain lignin. These fibers serve in the manufacture of paper and cloth and can be further categorized as follows.

• Seed fiber: The fiber is obtained from the seed, such as cotton and kapok.
• Leaf fiber: The fiber is derived from the leaf, such as sisal and agave.
• Bast fiber or skin fiber: The fiber is collected from the skin or bast surrounding the plant stem. These fibers have higher tensile strength than other fibers. They are therefore useful for durable yarn and fabric for packaging and paper. Examples include jute, kenaf, industrial hemp, ramie, rattan, soybean fiber, vine fiber, and banana fiber.
• Fruit fiber: The fiber is collected from the fruit of the plant, such as coconut fiber (coir).
• Stalk fiber: The fiber is derived from stalks of wheat, rice, barley, and other crops.

Animal fibers

Animal fibers are generally made of proteins. They can be subdivided as follows.

• Animal hair: Various fibers are obtained from hairy mammals. Examples include wool (from sheep), goat hair (alpaca, cashmere), horse hair, and so forth.
• Silk fiber: This type of fiber is collected from the dried saliva of insect larvae that prepare cocoons. The main example is silk from silkworms.
• Avian fiber: Some fibers are obtained from birds. Examples are feathers and feather fiber.
• Catgut: It is derived mainly from sheep intestines.
• Sinew: Fibers obtained from animal tendons.

Mineral fibers

Mineral fibers may be used in their naturally occurring form or slightly modified before use. These fibers can be categorized as follows.

• Asbestos: It is the only naturally occurring, long mineral fiber. Varieties are serpentine (chrysolite) and amphiboles (amosite, crocidolite, tremolite, actinolite, and anthophyllite). (Short, fiberlike minerals include wollastinite, attapulgite, and halloysite.)
• Ceramic fibers: Glass fibers (glass wool and quartz), aluminum oxide, silicon carbide, and boron carbide.
• Metal fibers: Some metals may be drawn out into fibers. An example is aluminum fibers.

Manmade fibers

Manmade fibers may come from natural raw materials or synthetic chemicals.

• Many types of fiber are manufactured from natural cellulose, including rayon, modal, and the more recently developed Lyocell. Cellulose-based fibers are of two types, regenerated or pure cellulose such as from the cupro-ammonium process and modified or derivitized cellulose such as the cellulose acetates. Fiberglass made from specific glass formulas and optical fiber, made from purified natural quartz, are also man-made fibers that come from natural raw materials. Metallic fibers can be drawn from ductile metals such as copper, gold or silver and extruded or deposited from more brittle ones such as nickel, aluminum or iron.
• Synthetic fibers are a subset of man-made fibers, which are based on synthetic chemicals (often from petrochemical sources) rather than arising from natural materials by a purely physical process. Such fibers are made from polyamide nylon, PET or PBT polyester, phenol-formaldehyde (PF),polyvinyl alcohol fiber (PVOH), polyvinyl chloride fiber (PVC), polyolefins (PP and PE), or acrylic polymers, although pure polyacrylonitrile PAN fibers are used to make carbon fiber by roasting them in a low oxygen environment. Traditional acrylic fiber is used more often as a synthetic replacement for wool. Carbon fibers and PF fibers are noted as two resin-based fibers that are not thermoplastic, most others can be melted. Aromatic nylons such as Kevlar and Nomex thermally degrade at high temperatures and do not melt. More exotic fibers have strong bonding between polymer chains (e.g. aramids), or extremely long chains (e.g. Dyneema or Spectra). Elastomers can even be used, e.g. spandex although urethane fibers are starting to replace spandex technology.

Coextruded fibers have two distinct polymers forming the fiber, usually as a core-sheath or side-by-side. Coated fibers exist such as nickel-coated to provide static elimination, silver-coated to provide anti-bacterial properties and aluminum-coated to provide radar chaff. Radar chaff is actually a spool of continuous glass tow that has been aluminum coated. An aircraft-mounted high speed cutter chops it up as it spews from a moving aircraft to foil radar signals.

Micro fibers in textiles refer to sub-denier fiber (such as polyester drawn to 0.5 dn). Denier and Detex are two measurements of fiber yield based on weight and length. If the fiber density is known you also have a fiber diameter, otherwise it is simpler to measure diameters in micrometres. Microfibers in technical fibers refer to ultrafine fibers (glass or meltblown thermoplastics)often used in filtration. Newer fiber designs include extruding fiber that splits into multiple finer fibers. Most synthetic fibers are round in cross-section, but special designs can be hollow, oval, star-shaped or trilobal. The latter design provides more optically reflective properties. Synthetic textile fibers are often crimped to provide bulk in a woven, nonwoven or knitted stucture. Fiber surfaces can also be dull or bright. Dull surfaces reflect more light while bright tends to transmit light and make the fiber more transparent.

Very short and/or irregular fibers have been called fibrils. Natural cellulose, such as cotton or bleached kraft show smaller fibrils jutting out and away from the main fiber structure.

Uses of fibers

• Papermaking: Wood fibers are treated by combining them with other additives. They are then processed into a network of wood fibres, which constitutes the sheet of paper. The end paper product (paper, paperboard, tissue, etc.) dictates the species, or species blend, that is best suited to provide the desirable sheet characteristics, and also dictates the required fiber processing (chemical treatment, heat treatment, mechanical 'brushing' or refining etc.).

• Cloth making

• String, rope

• Data communications by optical fibers: An optical fiber is a glass or plastic fiber designed to guide light along its length by total internal reflection. Fiber optics is the branch of applied science and engineering concerned with such optical fibers. Optical fibers are widely used in fiber-optic communication, which permits digital data transmission over longer distances and at higher data rates than electronic communication. They are also used to form sensors, and in a variety of other applications.

Dietary fiber

Dietary fibers are the indigestible portion of plant foods that move food through the digestive system, absorbing water. Chemically, dietary fiber consists of non-starch polysaccharides and several other plant components such as cellulose, lignin, waxes, chitins, pectins, beta-glucans, inulin and oligosaccharides.

Dietary fibers are usually divided into categories of “insoluble” and “soluble”, based on their solubility in water. Both types are present in all plant foods, with varying degrees of each according to a plant’s characteristics. Insoluble fibers have passive, water-attracting properties that help increase bulk, soften stools, and shorten transit time through the intestinal tract. Soluble fibers undergo active, metabolic processing to yield end-products with broad, significant health effects.

See also

• Dietary fiber
• Optical fiber
• Plastic
• Textile

References

ISBN links support NWE through referral fees

• Jeff Hecht, City of Light: The Story of Fiber Optics, Oxford University Press, New York (1999). ISBN 0-19-510818-3.
• Jeff Hecht, Understanding Fiber Optics (5th Edition), Prentice Hall (2005). ISBN 0131174290.
• Peter Morgan, Carbon Fibers and Their Composites, CRC Press, Boca Raton, Florida (2005). ISBN 0824709837.
• Shirley S. Lorenzani, Dietary Fiber Keats Publishing, New Canaan, Connecticut (1998). ISBN 087983479X.

External links

• How is paper made?
• Paper Online
• How Paper Is Made
• American Heart Association - Dietary Fiber
• International Jute Study Group

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

• Fiber  ^history
• Dietary_fiber  ^history
• Wood_fiber  ^history
• Optical_fiber  ^history
• Natural_fiber  ^history

The history of this article since it was imported to New World Encyclopedia:

• History of "Fiber"

Note: Some restrictions may apply to use of individual images which are separately licensed.