Fibers, synthetic twentieth century

Fibers (see Fibers, survey) used in textile production can have a wide variety of origins plants, ie, ceUulosic fibers (see Fibers, cellulose esters) animals, ie, protein fibers (see Wool) and, in the twentieth century, synthetic polymers. Depending on the part of the plant, the ceUulosic fibers can be classified as seed fibers, eg, cotton (qv), kapok bast fibers, eg, linen from flax, hemp, jute and leaf fibers, eg, agave. Protein fibers include wool and hair fibers from a large variety of mammals, eg, sheep, goats, camels, rabbits, etc, and the cocoon material of insect larvae (sUk). Real sUk is derived from the cocoon of the silkworm, Bombjx mori and for a long time was only produced in China, from which it was traded widely as a highly valuable material. 

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. 

The first fibers used by humans were probably those that occur naturally as tissues or excretions of either vegetables or animals (see Table 87). At much later times, after metals had been discovered, humans also learned to manufacture - from some of the ductile metals, mainly gold, silver, and their alloys - thin filaments (not fibers, however), which have since been used to decorate textile fabrics. It was only during the twentieth century, after synthetic plastics were discovered, that it became possible to make artificial human made fibers. The great majority of the natural fibers, such as cotton and wool, occur as staple fibers, short fibers whose length is measured in centimeters. Silk is different from all other natural fibers in that it occurs as extremely long and continuous filaments several hundred meters long. 

In this chapter we examine the recent history of synthetic fiber production, provide a convenient classification of fibers, and then introduce the subject of strong and stiff fibers. Strong and stiff fibers came about in the second half of the twentieth century because of many improvements in synthesis and processing,... 

The last quarter of the twentieth century saw tremendous advances in the processing of continuous, fine diameter ceramic fibers. Figure 6.4 provides a summary of some of the important synthetic ceramic fibers that are available commercially. We have included in Fig. 6.4 two elemental fibers, carbon and boron, while we have excluded the amorphous, silica-based glasses. Two main categories of synthetic ceramic fibers are oxide and nonoxides. A prime example of oxide fibers is alumina while that of nonoxide fibers is silicon carbide. An important subclass of oxide fibers are silica-based glass fibers and we devote a separate chapter to them because of their commercial importance (see chapter 7). There are also some borderline ceramic fibers such as the elemental boron and carbon fibers. Boron fiber is described in this chapter while carbon fiber is described separately, because of its commercial importance, in Chapter 8. 

This book is about materials in fibrous form, precisely what the title says. Perhaps the only thing that needs to be emphasized is that the materials aspects of fibers are highlighted. The main focus is on the triad of processing, microstructure, and properties of materials in a fibrous form. I have kept the mathematics to the bare minimum necessary. More emphasis is placed on physical and chemical insights. Although all kinds of fibers are touched upon, there is a distinct tilt toward synthetic, nonapparel-type fibers. This is understandable inasmuch as the second half of the twentieth century has seen tremendous research and development activity in this area of high performance fibers, mainly for use as a reinforcement in a variety of matrix materials. 

Before the development of synthetic polymers, people were limited to using natural substances such as stone, wood, metals, wool, and cotton. By the turn of the twentieth century, a few chemically treated natural polymers such as rubber and the first plastic, celluloid, had become available. Celluloid is made by treating cellulose from cotton or wood fiber with nitric acid. 

Worldwide production of fibers was c t. 45 10 t/a in 1993, of which ca. 20% was inorganic fibers. Whereas at the turn of the twentieth century the fibers utilized were almost exclusively natural fibers (organic fibers cotton, sheep s wool and silk inorganic fibers asbestos), by 1993 the proportion of synthetic fibers had grown to ca. 50%. This trend appears to parallel the increasing world population and the consumer behavior coupled therewith. 

Around the turn of the twentieth century, modern atomic theory wreis developed, and chemistry became a mainstream science through which new materials could be produced. Each new material engendered new apphcations, and each new application played to a demand for stiU newer materials, mostly derived from coal tar, of which a ready supply existed. The final key requirementwreis the discovery and development of polymerization. The first completely synthetic polymer, compounded from phenol and formaldehyde, was developed in 1907 by Belgian chemist Leo Hendrik Baekeland. It proved to be the elusive material needed to expedite the mass production of consumer goods. Soon, many other new materials were created from polymerization, which led to the development of the modem plastics industry. These versatile resin materials were used in a variety of applications, from the synthetic fibers used to make cloth to essential structural components of modern space and aircraft. 

Fibers have been used for thousands of years, but not until the nineteenth and twentieth centuries did chemically modihed natural hbers (cellulose) and synthetic plastic or polymer hbers become extremely important, opening new helds of application. Advanced composite materials rely exclusively on synthetic hbers. Research has also produced new applications of natural materials such as glass and basalt in the form of hbers. The current king among hbers is carbon, and new forms of carbon, such as carbon nanotubes, promise to advance fiber technology even further. 

As polymer science developed in the twentieth century, new and entirely synthetic materials were discovered that could be formed into fine fibers. Nylon-66 was invented in 1935 and Teflon in 1938. Following World War II, the plastics industry grew rapidly as new materials and uses were invented. The immense variety of polymer formulations provides an almost limitless array of materials, each with its own unique characteristics. The principal fibers used today are varieties of nylons, polyesters, polyamides, and epoxies that are capable of being produced in fiber form. In addition, lai e quantities of carbon and glass fibers are used in an ever-growing variety of functions. 

Although an early synthetic plastic derived from cellulose was introduced in Europe in the nineteenth century, it was not until the twentieth century that the modem plastics industry was bom, with the introduction of Bakelite, which found apphcations in the manufacture of telephones, phonograph records, and a variety of varnishes and enamels. Thermoplastics, such as polyethylene, polystyrene, and polyester, can be heated and molded, and bUhons of pounds of them are produced in the United States annually. Polyethylene, a low-weight, flexible material, has many applications, including packj ing, electrical insulation, housewares, and toys. Polystyrene has found uses as an electrical insulator and, because of its clarity, in plastic optical components. Polyethylene terephthalate (PET) is an important polyester, with applications in fibers and plastic bottles. Polyvinyl chloride (PVG) is one of the most massively manufec-tured synthetic polymers. Its early apphcations were for raincoats, umbrellas, and shower cmtains, but it later found uses in pipe fittings, automotive parts, and shoe soles. 

Natural fibers were used long before the discovery of the synthetics in the twentieth century. Natural fibers are usually composed of either cellulose or protein, as shown in Table 6.11. Animal hair fibers belong to a class of proteins known as keratin, which serve as the protective outer layer of the higher vertebrates. The silks are partly crystalline protein fibers. The crystalline por-... 

Perhaps the greatest advances in materials made during the twentieth century have been in polymer science. The invention of nylon in 1938 by Wallace Carothers at Dupont laid the foimdation for the synthetic fiber industry and the miracle fabrics we enjoy today. Leo Baekeland developed a method for producing bakelite (phenol formaldehyde), the first thermosetting plastic, in 1909. This material was the forerunner of the enormous plastics industry that developed during and after World War 11. Other polymer products from S5mthetic rubber to adhesives and coatings have found their way into virtually every aspect of our present day lifestyle. 

Early in the twentieth century, the chemical industry was considered to have two parts the manufacture of inorganic chemicals and the manufacture of organic chemicals. Today, the Standard Industrial Classification (SIC Index) of the United States Bureau of the Census defines Chemical and Allied Products as comprising three general classes of products (1) basic chemicals such as acids, alkalis, salts, and organic chemicals (2) chemicals to be used in further manufacture such as synthetic fibers, plastics materials, dry colors, and pigments and (3) finished chemical products to be used for ultimate consumer consumption as architectural paints, drugs, cosmetics, and soaps or to be used as materials or supplies in other industries such as industrial paints, adhesives, fertilizers, and explosives. An even broader description that is often considered is that of the chemical... 

Since late twentieth century, manufactured protein fibers with different stmc-tures and properties are being developed with new technologies, such as the use of chemical and biochemical treatments and the spinning of protein/synthetic polymer bicomponent fibers. Figure 5.21 shows a SEM image of a core-sheath soybean protein/polyvir rl alcohol bicomponent fiber. 

Many manufactured protein fibers were commercialized in mid-twentieth century. However, due to technical and economic problems, manufactured protein fibers were not able to compete with either natural fibers or the newly development synthetic fibers at that time. All manufactured protein fibers developed in mid-twentieth century eventually were abandoned by manufacturers. 

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