Natures Fibers

Fibers can be divided into two general classes crystalline or amorphous. These may be further divided into four more classes natural organic, synthetic organic, natural mineral, and synthetic mineral fibers. Perhaps the word mineral should be reserved for natural substances only, but definitions here have also become so loose that all liquid and solid inorganic substances are referred to as minerals. In usage adopted for this book an effort will be made to differentiate between natural and synthetic fibers. 

Most organic fibers are amorphous or semiciystalline. Mineral fibers are highly crystalline or amorphous. Most natural mineral fibers are highly crystalline while most synthetic mineral fibers are amorphous (fiber glass, spun slag, or 

Fibrous materials have been indispensable to humanity from the earliest tribes to modem global societies. National economies have depended upon fibers such as cotton, wool, silk, flax, hemp, and wood as their primary items of commerce. Most natural fibers are intentionally grown in a selective agricultural project and are harvested in much the same way other farm products are cultivated and harvested. 

Blocks were supposedly done to help cotton farmers, though simultaneously, limits were placed upon quantities of cotton that could be grown. Cotton cord tires were a menace to all society. They were biodegradable and often failed catastrophically at moments of disaster. Few reasonable people would desire that we return to days of natural cotton tire cord or natural rubber automobile tires. These tire s life expectancy was about twenty thousand miles, under the best of conditions, but they were highly susceptible to flats and blowouts, shortening their useful lives 

Synthetic organic fibers have been used to replace mineral fibers in some application since mineral fibers have come under attack. Natural serpentine fibers are mined from Earth and are therefore relatively inexpensive when compared to synthetic organic fibers. Aramid polymers, Kevlar , have been substituted for serpentine minerals in automobile brakes and seem to be reasonably effective, but expensive. 

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In terms of the number of scientists and engi neers involved research and development in polymer chemistry is the principal activity of the chemical in dustry The initial goal of making synthetic materials that are the equal of natural fibers has been more than met it has been far exceeded What is also im... 

In general, the geometric properties of the natural fibers are highly variable from fiber to fiber, both within a given lot and among lots of the same fiber type. In the synthetic fibers, the geometric properties are extremely uniform in view of the production control possible in a chemical plant but not in an agricultural product. 

The physical properties of these fibers are compared with those of natural fibers and other synthetic fibers in Table 1. Additional property data may be found in compilations of the properties of natural and synthetic fibers (1). Apart from the polyolefins, acryhcs and nylon fibers are the lightest weight fibers on the market. Modacryhcs are considerably more dense than acryhcs, with a density about the same as wool and polyester. 

Staple is produced by cutting a crimped tow into short lengths (usually 4—5 cm) resembling short, natural fibers. Acetate and triacetate staple are shipped in 180—366 kg bales, but production is quite limited. Conventional staple-processing technology appHed to natural fibers is used to process acetate and triacetate staple into spun yam. 

Fibers for commercial and domestic use are broadly classified as natural or synthetic. The natural fibers are vegetable, animal, or mineral ia origin. Vegetable fibers, as the name implies, are derived from plants. The principal chemical component ia plants is cellulose, and therefore they are also referred to as ceUulosic fibers. The fibers are usually bound by a natural phenoHc polymer, lignin, which also is frequentiy present ia the cell wall of the fiber thus vegetable fibers are also often referred to as lignocellulosic fibers, except for cotton which does not contain lignin. 

J. G. Cook, Handbook of Textile Fibers I. Natural Fibers, 5th ed., Merrow Publishing, Durham, UK, 1984. 

Thermoplastic Fibers. The thermoplastic fibers, eg, polyester and nylon, are considered less flammable than natural fibers. They possess a relatively low melting point furthermore, the melt drips rather than remaining to propagate the flame when the source of ignition is removed. Most common synthetic fibers have low melting points. Reported values for polyester and nylon are 255—290°C and 210—260°C, respectively. 

In conjunction with the increased use of synthetic fibers and blends of synthetic and natural fibers, and the modernisation of appHcation processes which has taken place simultaneously, the technique of textile whitening has been improved considerably. 

A selection of fiber property data is given ia Table 2 as an illustration of the range of fiber properties available commercially for use ia manufacturiag nonwoven fabrics. In general, fiber diameters range from 5 to >40 p.m for natural fibers, and from less than 10 p.m (microdenier) to as high as needed for manufactured fibers. 

Bags of various constmctions are used in the storage and transportation of dry chemicals. The choice of which type of bag to use should be based on the needs of the product for adequate protection and the requirements of the distribution network. To a certain degree, bags can be custom-made for a particular product indeed, almost any shipping requirement can be satisfied by one of many combinations of paper, plastic, and natural fibers incorporated in the design of bags. 

Textile. Textile bags are made from natural fibers such as cotton and burlap (see Fibers, vegetable). Burlap or Hessian cloth is woven from jute fibers. Because the supply of jute and, consequendy, its price have been uncertain for many years, textile bags gradually have been replaced by various combinations of textile components with plastic or paper, multiwaH paper bags, or plastic bags (see Textiles). 

Staple is used directly in the manufacturing of nonwoven fabrics (qv) (127) and spun into yam through the cotton, worsted, and woolen systems in 100% form or in blends with other synthetic or natural fibers (128,129). 

Nonabsorbable Natural Sutures. Cotton and silk are the only nonabsorbable sutures made from natural fibers that are stiH available ia the United States. Cotton suture is made from fibers harvested from various species of plants belonging to the genus Gossipium. The fiber is composed principally of ceUulose. The seeds are separated from the cotton boUs, which are carded, combed, and spun iato yams that are then braided or twisted to form sutures ia a range of sizes (Table 4). The suture is bleached with hydrogen peroxide and subsequendy coated (finished or glaced) with starch and wax. The suture may be white or dyed blue with D C Blue No. 9. 

Fibers have been used by humans for thousands of years, but only in the twentieth century has there been such an explosion in fiber types available to the textile manufacturer. The advent of synthetic fibers possessing improved resiliency and dimensional stability has placed natural fibers, particularly cotton (qv), at an ostensible disadvantage. Before synthetics, various means to control the shrinkage, dimensional stability, and smooth-dry performance of cotton had been investigated, but the appearance of synthetics such as polyester has placed a greater sense of urgency on cotton interests to focus on the perceived deficiencies of natural fibers. 

Treatments with Chemicals or Resins. Resin treatments are divided into topical or chemical modifications of the fiber itself. Most chemical treatments of synthetic fibers are topical because of the inert character of the fiber itself and the general resistance of the fiber to penetration by reagents. By contrast, ceUulosics and wool possess chemical functionality that makes them reactive with reagents containing groups designed for such purchases. Natural fibers also provide a better substrate for nonreactive topical treatments because they permit better penetration of the reagents. 

Early waterproofing treatments consisted of coatings of a continuous layer impenetrable by water. Later water-repellent fabrics permitted air and moisture passage to improve the comfort of the wearer. Aluminum and zirconium salts of fatty acids, siUcone polymers, and perfluoro compounds are apphed to synthetic as well as natural fibers. An increase in the contact angle of water on the surface of the fiber results in an increase in water repeUency. Hydrophobic fibers exhibit higher contact angles than ceUulosics but may stiU require a finish (142). 

ASTM D629 describes procedures for determining cross-sectional shapes for natural fibers using microscopic analysis. Cross-sectional shape of synthetic fibers also can be verified by using microscopic analysis. 

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