纺织英语第三版课文翻译电子版课文.doc

Lesson OneCotton Growing Cotton is the worlds most widely used fiber. Its popularity stems from both its relative ease of production and its applicability to a wide variety of textile products. The price of cotton yarn, however, is strongly dependent upon the cost of labor, so that in the industrialized nations, where labor is expensive, cotton yarns may be relatively high priced. Until relatively recent times, however, cotton was not as widely used as wool and linen. This was because it was easier to spin wool or flax into yam because of their greater length. In addition, cotton fibers have to be separated from the seeds to which they cling. This procedure was very tedious and time-consuming when done by hand. Early machinery could be used on only the longest staple cotton. So labor costs tended to be very high. The invention of the saw-type cotton gin made possible the exploitation of the short staple fiber, which thrived in the Carolinas and Virginia of the United States. The dramatic increase in productivity, coupled with the low cost of labor in the southern United States, gave cotton a continually expanding portion of the world textile market. Increasing mechanization of fiber and yarn production helped keep the cost of cotton goods low. The, development of the textile machinery enlarged the production base. Cotton cultivation requires warm climates with a high level of moisture or irrigation. The growing season is from six to seven months long. During this period the seeds sprout and grow, producing a white blossom in about 100 days. The blossom produces a seed pod, which matures during the next two months. When the pod bursts, the cotton fibers are ready for picking. Before yam manufacture, cotton is graded, sorted, and blended to insure uniform yam quality. Cotton is graded on the basis of color, staple length, fineness, and freedom from foreign matter. In the United States, cottons are divided into grades according to length of staple, uniformity, strength, color, cleanness and flexibility. These are pared with a standard supplied by the United States Department of Agriculture. The standard provides 6 grades above and 6 grades below the Middling grade. The most mon grades are: (1) Strict good middling.(2) Good middling.(3) Strict middling.(4) Middling.(5) Strict low middling(6) Low middling. (7) Strict good ordinary. The cotton fiber may be from 0.3 to 5.5 cm long. Under the microscope it appears as a ribbon like structure that is twisted at irregular intervals along its length. The twists, called convolutions, increase the fiber-to-fiber friction necessary to secure a strong spun yarn. The fiber ranges in color from a yellowish to pure white, and may be very lustrous. However, most cotton dull. A cross-sectional view reveals that the fiber is kidney-shaped with central hollow core known as the lumen. The lumen provides a channel for nutrients while the plant is growing. The fiber consists of an outer shell, or cuticle, which surrounds the primary wall. The primary wall, in turn, covers the secondary wall surrounding the lumen. The cuticle is a thin, hard shell which protects the fiber from bruising and damage during growth. In use as a textile fiber, the cuticle provides abrasion resistance to cotton.Lesson TwoCotton Properties and Uses A relatively high level of moisture absorption and good wicking properties help make cotton one of the more fortable fibers. Because of the hydroxyl groups in the cellulose, cotton has a high attraction for water. As water enters the fiber, cotton swells and its cross section bees more rounded. The high affinity for moisture and the ability to swell when wet allow cotton to absorb about one-fourth of its weight in water. This means that in hot weather perspiration from the body will be absorbed in cotton fabrics, transported along the yarns to the outer surface of the cloth and evaporated into the air. Thus, the body will be aided in maintaining its temperature. Unfortunately, the hydrophilic nature of cotton makes it susceptible to water-borne stains. Water-soluble colorants such as those in coffee or grape juice will penetrate the fiber along with the water; when the water evaporates, the colorant is trapped in the fiber. Perhaps the major disadvantage to cotton goods is their tendency to wrinkle and the difficulty of removing wrinkles. The rigidity of cotton fiber reduces the ability of yarns to resist wrinkling. When the fibers are bent to a new configuration, the hydrogen bonds which hold the cellulose chains together are ruptured and the molecules slide in order to minimize the stress within the fiber. The hydrogen bonds reform in the new positions, so that when the crushing force is removed the fibers stay in the new positions. It is the rupture and reformation of the hydrogen bonds that helps to maintain wrinkles, so that cotton goods must be ironed. Cotton is a moderately strong fiber with good abrasion resistance and good dimensional stability. It is resistant to the acids, alkalies, and organic solvents normally available to consumers. But since it is a natural material, it is subject to attack by insects, molds and fungus. Most prominent is the tendency for cotton to mildew if allowed to remain damp. Cotton resists sunlight and heat well, although direct exposure to constant strong sunlight will cause yellowing and eventual degradation of the fiber. Yellowing may also occur when cotton goods are dried in gas dryers. The color change is the result of a chemical reaction between cellulose and oxygen or nitrogen oxides in the hot air in the dryer. Cottons will retain their whiteness longer when line-dried or dried in the electric dryer. Of major interest is the fact that cotton yarn is stronger when wet than when dry. This property is a consequence of the macro-and micro-structural features of the fiber. As water is absorbed, the fiber swells and its cross section bees more rounded. Usually the absorption of such a large amount of foreign material would cause a high degree of internal stress and lead to weakening of the fiber. In cotton, however, the absorption of water causes a decrease in the internal stresses. Thus, with less internal stresses to overe, the swollen fiber bees stronger. At the same time, the swollen fibers within the yarns press upon each other more strongly. The internal friction strengthens the yarns. In addition, the absorbed water acts as an internal lubricant which imparts a higher level of flexibility to the fibers. This accounts for the fact that cotton garments are more easily ironed when damp. Cotton fabrics are susceptible to shrinkage upon laundering. Perhaps more than any other fiber, cotton satisfies the requirements of apparel, home furnishings, recreational, and industrial uses. It provides fabrics that are strong, lightweight, pliable, easily dried, and readily laundered. In apparel, cotton provides garments that are fortable, readily dried in bright, long-lasting colors, and easy to care for. The major drawbacks are a propensity for cotton yams to shrink and for cotton cloth to wrinkle. Shrinkage may be controlled by the application of shrink-resistant finishes. Durable-press properties may be imparted by chemical treatment or by blending cotton with more wrinkle-resistant fibers, such as polyester. In home furnishings, cotton serves in durable, general-service fabrics. Although they may lack the formal appearance of materials made from other fibers, cotton goods provide a fortable, homey environment. Cotton fabrics have been the mainstay of bed linens and towels for decades, because they are fortable, durable, and moisture-absorbent. Polyester/cotton blends provide the modern consumer with no-iron sheets and pillowcases that retain a crisp, fresh feel. For recreational use, cotton has traditionally been used for tenting and camping gear, boat sails, tennis shoes and sportswear. Cotton is particularly well-suited for tent. A tent fabric must be able to breath, so that the occupants are not smothered in their own carbon dioxide. Furthermore, exchange of air with the outside atmosphere reduces the humidity within the tent and keeps it from being stuffy. Fabrics woven from cotton can be open enough to provide good air permeability for fort. Tents should also shed water, when wet by rain, cotton yarns swell, reducing the interstices between the yarns and resisting the penetration of water. Today, however, heavy canvas gear is being supplanted by light-weight nylon in tenting equipment. Cotton cord, twine and ropes are used in industry to bind, hold, and lash all kinds of things, from bales to boats. Cotton yarns are used to reinforce belts on drive motors and in work clothing.Lesson FourWool The early history of wool is lost in antiquity. Sheepskin, including the hair, was probably used long before it was discovered that the fibers could be spun into yarns or even felted into fabric. There is no evidence to support the theory that wool was the first fiber to be processed into fabric, but it seems certain that, as a part of the skin, wool was used for covering and protection by prehistoric peoples long before yarns and fabrics were made.The earliest fragments of wool fabric have been found in Egypt, probably because of the preserving qualities of the climate. These have been dated from 4000 to 3500 B C. The earliest example of wool fabric found in Europe has been dated about 1500 B C; it was unearthed in archeological digs in Germany. Danish sites have yielded excellent fragments of early wool fabrics dated about 1300 to 1000 BC. These fabrics are rough and coarse and contain considerable wild sheep hair. Wool is a natural fiber of animal origin. Though vegetable fibers were probably the first to be used for spinning and weaving into cloth, animal fibers in the form of skins were the earliest type of clothing worn by man. There are indications that, as early as the seventh century BC, people began to sell and buy woolen goods. The supply of wool available to the world every year amounts to about 5000 million pounds. After scouring, this is reduced to about 3000 million pounds of pure wool. The wool crop is insufficient to meet the world needs. Pure wool is often mixed with other type fibers and recovered wool to meet the demand. The qualities of different wools vary greatly. The merino sheep of Australia, South America and South Africa produce very free and soft wool. The quality of wool from these sources depends upon the conditions and heritage of the sheep. Port Philip wool is the finest in Australia and is used to produce the highest quality woolen and worsted fabrics. Wool from South Africa is very wavy with a good white color and is used for good quality worsted and woolen goods. South American wool is usually of lower quality than wool from Australia or South Africa. Merino wool has been successfully raised in Germany, France, Spain and the United States and is of high quality. To provide the freest-quality wool, production is scientifically controlled. Sheep are inoculated against disease, dipped in chemicals to protect them against insects, and unless on rangeland, fed diet designed to produce healthy animals. Wool can be sheared from the living animal or pulled from the hide after the animal has been slaughtered for its meat. Sheared wool is called fleece or clip wool and is quality to pulled wool, which is taken from the hides of slaughtered sheep Wool considered superior Shearing is currently done very rapidly with power shears. A good worker can pletely shear a sheep in less than one minute, sometimes as short as 20 seconds. Recent developments in Australia have led to a process called chemical or biological shearing. The animal is fed a chemical similar to that used in the treatment of cancer, which cause the hair to fall out within two weeks. Within very short time following the loss of the hair, it starts to grow again, and the sheep suffer no damage. Fibers obtained in this way are slightly longer than those sheared from the animal, and there appears to be less physical damage to the fibers. Usually shearing is done once a year in the early spring, and the fleece is removed in one piece, rolled, packed into bags, and shipped to the nearest processing center. Pulled wool is removed from the hide by one of two methods. It may be treated with a depilatory that loosens the fiber and permits it to be pulled away from the skin without damaging the hide, or it Can be loosened by the action of bacteria on the root end of the fiber. Pulled wool is usually mixed with fleece or clip wool before processing into yarns and fabrics. Preliminary grading of wool fibers is done while they are still in the fleece, because this step is important in determining cost. Factors used in determining the grade of wool include fiber fineness or diameter and length, the age of the animal, the natural color, the breed of the sheep, and the condition under which the animal lived. After grading, fleeces are shipped to the mill, where they are prepared for further processing into yarns and fabrics. Wool is attacked by hot sulfuric acid and deposes pletely. most other mineral acids of all strengths. Wool will dissolve in caustic soda solutions that would have little effect on cotton.Lesson Five Structure and Properties of Wool Under the microscopic observation, the length of the wool fiber shows a scale structure. The size of the scale varies from very small to paratively broad and large. As many as 700 scales are found in 1 cm of fine wool, whereas coarse wool may have as few as 275 per cm. Fine wool does not have as clear and distinct scales as coarse wool, but they can be identified under high magnification. A cross section of wool shows three distinct parts to the fiber. The outer layer, called cuticle, is posed of the scales. These scales are somewhat horny and irregular in shape, and they overlap, with the top pointing towards the tip of the fiber; they are similar to fish scales. The major portion of the fiber is the cortex (posed of cortical cells ); this extends toward the center from the cuticle layer. Cortical cells are long and spindle-shaped and provide fiber strength and elasticity. The cortex accounts for approximately 90 percent of the fiber mass. In the center of the fiber is the medulla. The size of the medulla varies and in fine fibers may be invisible. This is the area through which food reached the fiber during growth, and it contains pigment that gives color to fibers. Wool fibers vary in length from 3.8 to about 38 cm. Most authorities have determined that fine wools are usually from 3.8 to 12.7 cm; medium wool from 6.4 to 15.2 cm; and long (coarse) wools from 12.7 to 38 cm. The width of wool also varies considerably. Fine fibers such as M