16 From Natural Fibers to Man-Made Plastics 16.1.History and Classifications Fibers Natural fibers were utilized by mankind considerably earlier than metals,alloys,and ceramics.Indeed,it can be reasonably as- sumed that fibers were applied by humans long before recorded history.Moreover,even some animals use fibers,for example, when building nests (birds,mammals),webs (spiders),for pro- tection during pupation(caterpillars,silkworms),or for retriev- ing insects out of narrow holes (chimpanzees).In short,some animals produce fibers for their needs,whereas others collect them.The history of the utilization of fibers is,however,much harder to trace than that of metals and ceramics because fibers often deteriorate through rot,mildew,and bacterial action.In other words,only a few specimens of early fibers have been found so far. The first raw material that man turned into fabrics was prob- ably wool.Scholars assume that this might have occurred as early as during the Paleolithic period,that is,during the Old Stone Age, about 2 million years ago(see Chapter 1).Fabric from wool may have been produced by felting,a process that yields a nonwoven mat upon the application of heat,moisture,and mechanical ac- tion to some animal fibers,as will be explained in Section 16.2. That there was trade in wool can be inferred from documents and seals dating back to 4200 B.C.which have been found in Tall al- Asmar (Iraq).Breeding and raising wool-producing sheep appar- ently commenced in Central Asia and spread from there to other areas of the world.This was possible by the fact that sheep adapt easily to different climates.For example,it is reported that the Phoenicians brought the ancestors of the Merino sheep from Asia
16 Natural fibers were utilized by mankind considerably earlier than metals, alloys, and ceramics. Indeed, it can be reasonably assumed that fibers were applied by humans long before recorded history. Moreover, even some animals use fibers, for example, when building nests (birds, mammals), webs (spiders), for protection during pupation (caterpillars, silkworms), or for retrieving insects out of narrow holes (chimpanzees). In short, some animals produce fibers for their needs, whereas others collect them. The history of the utilization of fibers is, however, much harder to trace than that of metals and ceramics because fibers often deteriorate through rot, mildew, and bacterial action. In other words, only a few specimens of early fibers have been found so far. The first raw material that man turned into fabrics was probably wool. Scholars assume that this might have occurred as early as during the Paleolithic period, that is, during the Old Stone Age, about 2 million years ago (see Chapter 1). Fabric from wool may have been produced by felting, a process that yields a nonwoven mat upon the application of heat, moisture, and mechanical action to some animal fibers, as will be explained in Section 16.2. That there was trade in wool can be inferred from documents and seals dating back to 4200 B.C. which have been found in Tall alAsmar (Iraq). Breeding and raising wool-producing sheep apparently commenced in Central Asia and spread from there to other areas of the world. This was possible by the fact that sheep adapt easily to different climates. For example, it is reported that the Phoenicians brought the ancestors of the Merino sheep from Asia Fibers From Natural Fibers to Man-Made Plastics 16.1 • History and Classifications
16.1.History and Classifications 327 Minor to Spain several millennia ago.Today,Merino sheep are raised essentially on all of the continents.New Zealand,for ex- ample,with a population of only 3.5 million people,hosts some 50 million sheep of various breeds,whose forebearers were in- troduced there by British settlers about 150 years ago. Wild sheep have long,coarse fibers (called hairs)and a softer undercoat of short and fine fibers which provides thermal insu- lation.The Merino sheep has been bred to eliminate the outer coat and the annual shedding,allowing instead a continuously growing fine and soft fleece which can be repeatedly shorn off. Fibers retrieved from plants likewise played an important role in early civilizations because of their usefulness for clothing,stor- age,shelter (e.g.,tents),and cordage.It is,however,not fully known when specific plants were first cultivated for fiber pro- duction.Nevertheless,some records indicate that hemp was pre- sumably the oldest cultivated plant for this purpose.Hemp was first grown in Southeast Asia,from where it spread to China in approximately 4500 B.C.Flax was probably cultivated in Egypt before 3400 B.C.,at which time the art of spinning and weaving linen was already well developed.Woven flax and wool fabrics were found at the sites of the "Swiss lake dwellers"dating back to the seventh and sixth centuries B.C. Cotton was spun in India as early as 3000 B.C.,as some finds in tombs of that time indicate.A Hindu hymn written around 1400 B.C.describes the fabrication of cotton yarn and the weav- ing of cotton cloth.In contrast,the Egyptians seem to have started the cultivation of cotton much later,that is,at about A.D. 600-700.From there cotton spread to the Greek mainland and to the Romans. The production of silk,that is,the cultivation of the larva of Bombyx mori(commonly called mulberry silkworm)is attributed to the Chinese empress,Hsi-ling Shih,who,in 2640 B.C.,discov- ered that the silk filament from a cocoon could be unwound. (Other sources claim that Japan,at about 3,000 B.C.,was the first country in which silkworms were domesticated.)The technique of silk-making (called sericulture)was kept a secret by the Chi- nese for about 3,000 years but eventually spread to Persia,Japan, and India.Legend has it that two Persian monks smuggled some silkworm eggs and seeds of the mulberry tree (on whose leaves the larva feed)out of China.This triggered a silk industry in Byzantium during the reign of emperor Justinian(A.D.527-565) and in Arabic countries beginning with the eighth century A.D. Eventually,the art of sericulture spread in the twelfth century to Italy and thus to Europe.Silk was and still is regarded even to- day as a highly esteemed,luxury fabric because it is the finest of
Minor to Spain several millennia ago. Today, Merino sheep are raised essentially on all of the continents. New Zealand, for example, with a population of only 3.5 million people, hosts some 50 million sheep of various breeds, whose forebearers were introduced there by British settlers about 150 years ago. Wild sheep have long, coarse fibers (called hairs) and a softer undercoat of short and fine fibers which provides thermal insulation. The Merino sheep has been bred to eliminate the outer coat and the annual shedding, allowing instead a continuously growing fine and soft fleece which can be repeatedly shorn off. Fibers retrieved from plants likewise played an important role in early civilizations because of their usefulness for clothing, storage, shelter (e.g., tents), and cordage. It is, however, not fully known when specific plants were first cultivated for fiber production. Nevertheless, some records indicate that hemp was presumably the oldest cultivated plant for this purpose. Hemp was first grown in Southeast Asia, from where it spread to China in approximately 4500 B.C. Flax was probably cultivated in Egypt before 3400 B.C., at which time the art of spinning and weaving linen was already well developed. Woven flax and wool fabrics were found at the sites of the “Swiss lake dwellers” dating back to the seventh and sixth centuries B.C. Cotton was spun in India as early as 3000 B.C., as some finds in tombs of that time indicate. A Hindu hymn written around 1400 B.C. describes the fabrication of cotton yarn and the weaving of cotton cloth. In contrast, the Egyptians seem to have started the cultivation of cotton much later, that is, at about A.D. 600–700. From there cotton spread to the Greek mainland and to the Romans. The production of silk, that is, the cultivation of the larva of Bombyx mori (commonly called mulberry silkworm) is attributed to the Chinese empress, Hsi-ling Shih, who, in 2640 B.C., discovered that the silk filament from a cocoon could be unwound. (Other sources claim that Japan, at about 3,000 B.C., was the first country in which silkworms were domesticated.) The technique of silk-making (called sericulture) was kept a secret by the Chinese for about 3,000 years but eventually spread to Persia, Japan, and India. Legend has it that two Persian monks smuggled some silkworm eggs and seeds of the mulberry tree (on whose leaves the larva feed) out of China. This triggered a silk industry in Byzantium during the reign of emperor Justinian (A.D. 527–565) and in Arabic countries beginning with the eighth century A.D. Eventually, the art of sericulture spread in the twelfth century to Italy and thus to Europe. Silk was and still is regarded even today as a highly esteemed, luxury fabric because it is the finest of 16.1 • History and Classifications 327
328 16.From Natural Fibers to Man-Made Plastics all natural fibers and its production is cumbersome,as will be described later.Chinese silk textiles manufactured during the Han dynasty (206 B.C.-A.D.220)have been found in Egypt,in graves located in northern Mongolia,and in Chinese Turkistan. During the years of the industrial revolution,that is,in the eighteenth and nineteenth centuries,a number of machines were invented and put into service which transferred spinning,weav- ing,and other fiber-processing techniques from individual homes to centralized factories with consequential economic hardships for some people and concomitant social upheavals.These ma- chines which produced relatively inexpensive fabrics triggered, however,an increase in fiber demand and production. In the 1880s,it was eventually learned how to dissolve cellu- lose (from soft wood)and to extrude the resulting substance through narrow nozzles to form regenerated cellulose fibers such as artificial silk,which was later called viscose or rayon (see Section 16.3).Actually,the first artificial silk is said to have been made in 1879 by J.W.Swan in England for filaments of light bulbs even before Edison came up with his version!The first rayon stockings for women were manufactured as early as 1910 in Germany.(In France,viscose was called "mother-in-law silk"because of its extremely high flammability.)From there it was only one more (but not so easy)step to create completely synthetic fibers(from coal or oil)such as nylon.2 These new prod- ucts challenged the monopoly of natural fibers for textile and in- dustrial uses.Still,even today,more than one-half of the world's fibers stem from natural sources,among which cotton consti- tutes the most important part (Figure 16.1).We shall return to these topics in Sections 16.3 and 16.4. Natural fibers are generally classified by their origin.The plant or vegetable fibers are mostly cellulose-based,that is,they con- sist of polymers derived from carbohydrates (i.e.,CnH2nOn) which are manufactured by the plant from water and carbon dioxide gas through photosynthesis.They include bast fibers from stems of plants (jute,flax,sunn,hemp,ramie),leaf fibers (sisal, New Zealand flax,henequen,abaca,istle),palm-type and brush fibers (coir,raffia,palmyra,piassava),seed and fruit-hair fibers (cotton,kapok),and,of course,wood from trees.Table 16.1 con- tains usage,price,and origin of some of these fibers. Among the animal fibers,which are protein-based,are wool, mostly from sheep.Specialty animal fibers include mohair from Actually,the first useful light bulb was invented by the German H. Goebel who,in 1854,inserted a carbonized bamboo fiber into an evac- uated glass flask exactly like Edison 25 years later. 2Generic name for polyamides
all natural fibers and its production is cumbersome, as will be described later. Chinese silk textiles manufactured during the Han dynasty (206 B.C.–A.D. 220) have been found in Egypt, in graves located in northern Mongolia, and in Chinese Turkistan. During the years of the industrial revolution, that is, in the eighteenth and nineteenth centuries, a number of machines were invented and put into service which transferred spinning, weaving, and other fiber-processing techniques from individual homes to centralized factories with consequential economic hardships for some people and concomitant social upheavals. These machines which produced relatively inexpensive fabrics triggered, however, an increase in fiber demand and production. In the 1880s, it was eventually learned how to dissolve cellulose (from soft wood) and to extrude the resulting substance through narrow nozzles to form regenerated cellulose fibers such as artificial silk, which was later called viscose or rayon (see Section 16.3). Actually, the first artificial silk is said to have been made in 1879 by J.W. Swan in England for filaments of light bulbs even before Edison came up with his version!1 The first rayon stockings for women were manufactured as early as 1910 in Germany. (In France, viscose was called “mother-in-law silk” because of its extremely high flammability.) From there it was only one more (but not so easy) step to create completely synthetic fibers (from coal or oil) such as nylon. 2 These new products challenged the monopoly of natural fibers for textile and industrial uses. Still, even today, more than one-half of the world’s fibers stem from natural sources, among which cotton constitutes the most important part (Figure 16.1). We shall return to these topics in Sections 16.3 and 16.4. Natural fibers are generally classified by their origin. The plant or vegetable fibers are mostly cellulose-based, that is, they consist of polymers derived from carbohydrates (i.e., CnH2nOn) which are manufactured by the plant from water and carbon dioxide gas through photosynthesis. They include bast fibers from stems of plants (jute, flax, sunn, hemp, ramie), leaf fibers (sisal, New Zealand flax, henequen, abaca, istle), palm-type and brush fibers (coir, raffia, palmyra, piassava), seed and fruit-hair fibers (cotton, kapok), and, of course, wood from trees. Table 16.1 contains usage, price, and origin of some of these fibers. Among the animal fibers, which are protein-based, are wool, mostly from sheep. Specialty animal fibers include mohair from 328 16 • From Natural Fibers to Man-Made Plastics 1Actually, the first useful light bulb was invented by the German H. Goebel who, in 1854, inserted a carbonized bamboo fiber into an evacuated glass flask exactly like Edison 25 years later. 2Generic name for polyamides
16.1.History and Classifications 329 50 spunod 40 Cotton 30 Polyester 20 FIGURE 16.1.World textile fiber production 1980-2000.Note:Poly- ester means here "noncel- 10 Rayon and acetate lulosic synthetic fibers." Silk≈0.15×109 pounds. Wool 可ax Hemp (Source:U.S.Department of Agriculture Outlook 808182838485868788899091929394Sil9798992000 Board/Economic Re- Year search Service/Nov 2002.) the fleece of the Angora goat (named after the ancient province of Angora,today's Ankara,in Turkey),cashmere wool(stemming from the fine and soft undercoat of Kashmir goats which live in the mountains of Asia),and camel hair (which is collected dur- ing molting).Other specialty animal fibers stem from the llama and the alpaca,which are close relatives of the camel and live predominantly in the high grasslands of the Andes in South America.Further,one uses hair from horses,cows,and angora rabbits.The highest regarded animal fiber,however,is silk,which is spun by a caterpillar as already mentioned above. The third category of natural fibers is comprised of those made from minerals.Asbestos3 is the major member of this group of about 30 crystalline magnesium silicates,of which chrysotile ac- counted for 95%of the world production.Asbestos is no longer utilized for general applications because of its health hazards to the lungs.The fire-resistant property of asbestos was apparently known already to the Greeks and was documented during the first century A.D.by a Roman historian.The Chinese knew about asbestos as Marco Polo reported in the thirteenth century A.D. 3Asbestos (Greek)=indestructible
the fleece of the Angora goat (named after the ancient province of Angora, today’s Ankara, in Turkey), cashmere wool (stemming from the fine and soft undercoat of Kashmir goats which live in the mountains of Asia), and camel hair (which is collected during molting). Other specialty animal fibers stem from the llama and the alpaca, which are close relatives of the camel and live predominantly in the high grasslands of the Andes in South America. Further, one uses hair from horses, cows, and angora rabbits. The highest regarded animal fiber, however, is silk, which is spun by a caterpillar as already mentioned above. The third category of natural fibers is comprised of those made from minerals. Asbestos3 is the major member of this group of about 30 crystalline magnesium silicates, of which chrysotile accounted for 95% of the world production. Asbestos is no longer utilized for general applications because of its health hazards to the lungs. The fire-resistant property of asbestos was apparently known already to the Greeks and was documented during the first century A.D. by a Roman historian. The Chinese knew about asbestos as Marco Polo reported in the thirteenth century A.D. 16.1 • History and Classifications 329 80 81 82 83 84 85 86 87 88 89 Year Wool Flax Rayon and acetate Polyester Cotton 50 40 30 20 Textile fiber production in billion pounds 10 0 Hemp 90 91 92 99 2000 93 98 94 Silk 97 FIGURE 16.1. World textile fiber production 1980–2000. Note: Polyester means here “noncellulosic synthetic fibers.” Silk 0.15 109 pounds. (Source: U.S. Department of Agriculture Outlook Board/Economic Research Service/Nov 2002.) 3Asbestos (Greek) indestructible
330 16.From Natural Fibers to Man-Made Plastics TABLE 16.1.Major sources of natural fibers,usage,and raw and retail prices Raw world market price (U.S.cents/pound) Principal growing Fiber Usage 1995/96 2000 countries Flax/linen Fine textiles,cordage, 18.5 58.2 Belgium,Netherlands, raw,retted yarn Russia,France,China Ramie Garment blend with 28.3 51.8 China,Taiwan,Korea, farm price cotton Philippines,Brazil Cotton Garments,paper, 75.6 51.8 China,USA,Pakistan, farm price explosives,oil,padding India,Uzbekistan,Brazil Wool Knitting yarn,tweeds, 192.5 75 Australia,New Zealand, 3"and up flannels,carpets, China,South Africa, blankets,upholstery,felts Russia,Argentina Retail price Fiber Retail price Fiber ($/1 pound,Sept 2003) Almost white cashmere $130.00 Superwash Merino wool $16.33 Fine baby camel 46.00 Ramie 14.10 Baby llama 40.80 Goat hair 11.88 Cultivated silk 40.80 Fine Shetland wool 11.14 Water retted flax 24.76 Moorit English wool 9.28 White alpaca 19.68 Dew retted flax 8.17 Fine mohair 17.45 Source:Department of Commerce,U.S.Census Bureau,Foreign Trade Statistics. Rubber Probably the most fascinating natural material,however,is rubber, also known by the Maya name caoutchouc.4 Knowledge of the elas- tic properties of rubber was brought to Europe in 1496 by Christo- pher Columbus,who observed inhabitants of Haiti playing with bouncing balls.Considerably later,in 1615,a Spanish explorer re- ported how"milk"(latex5)gathered from incisions made on specific tropical trees was brushed on cloaks,rendering them waterproof af- ter drying,or on earthen,bottle-shaped molds to produce contain- ers.It was not until 1735 that a French geographical expedition iden- tified caoutchouc as the condensed sap of the Hevea brasiliensis tree, today called the rubber tree,because rubber has the capability to erase (rub off)pencil marks.Hevea trees grow only about ten de- grees north or south of the equator and need heavy annual rainfalls of about 250 cm,that is,a tropical climate.The rubber tree is cul- tivated at present particularly in Malaysia,but also in Ceylon,South- east Asia,and West Africa.Wild rubber is still harvested in South America(Brazil,Peru). HCaa wood and o-chu weeping,i.e.,weeping wood. 5Latex (Latin)=fluid
Probably the most fascinating natural material, however, is rubber, also known by the Maya name caoutchouc. 4 Knowledge of the elastic properties of rubber was brought to Europe in 1496 by Christopher Columbus, who observed inhabitants of Haiti playing with bouncing balls. Considerably later, in 1615, a Spanish explorer reported how “milk” (latex5) gathered from incisions made on specific tropical trees was brushed on cloaks, rendering them waterproof after drying, or on earthen, bottle-shaped molds to produce containers. It was not until 1735 that a French geographical expedition identified caoutchouc as the condensed sap of the Hevea brasiliensis tree, today called the rubber tree, because rubber has the capability to erase (rub off) pencil marks. Hevea trees grow only about ten degrees north or south of the equator and need heavy annual rainfalls of about 250 cm, that is, a tropical climate. The rubber tree is cultivated at present particularly in Malaysia, but also in Ceylon, Southeast Asia, and West Africa. Wild rubber is still harvested in South America (Brazil, Peru). 330 16 • From Natural Fibers to Man-Made Plastics 4Caa wood and o-chu weeping, i.e., weeping wood. 5Latex (Latin) fluid. Rubber TABLE 16.1. Major sources of natural fibers, usage, and raw and retail prices Raw world market price (U.S. cents/pound) Principal growing Fiber Usage 1995/96 2000 countries Flax/linen Fine textiles, cordage, 18.5 58.2 Belgium, Netherlands, raw, retted yarn Russia, France, China Ramie Garment blend with 28.3 51.8 China, Taiwan, Korea, farm price cotton Philippines, Brazil Cotton Garments, paper, 75.6 51.8 China, USA, Pakistan, farm price explosives, oil, padding India, Uzbekistan, Brazil Wool Knitting yarn, tweeds, 192.5 75.0 Australia, New Zealand, 3" and up flannels, carpets, China, South Africa, blankets, upholstery, felts Russia, Argentina Retail price Fiber Retail price Fiber ($/1 /2 pound, Sept 2003) Almost white cashmere $130.00 Superwash Merino wool $16.33 Fine baby camel 46.00 Ramie 14.10 Baby llama 40.80 Goat hair 11.88 Cultivated silk 40.80 Fine Shetland wool 11.14 Water retted flax 24.76 Moorit English wool 9.28 White alpaca 19.68 Dew retted flax 8.17 Fine mohair 17.45 Source: Department of Commerce, U.S. Census Bureau, Foreign Trade Statistics