Textiles synthetic fibers: nylon, polyesters

Table 10.2 outlines the uses of acrylonitrile. One important use of acrylonitrile is in the polymerization to polyacrylonitrile. This substance and its copolymers make good synthetic fibers for the textile industry. Acrylic is the fourth largest produced synthetic fiber behind polyester, nylon, and... 

Cellulose acetate fiber was first marketed as artificial silk and found applications as tricot knits and woven fabrics in blouses, dresses, apparel linings, velvets, and decorative ribbons. The combined cellulose acetate and triacetate textile fiber production continued to grow until in 1971 it peaked at 426,000 MT worldwide. The impact of synthetic fibers, namely polyester and nylon, during the 1970s was significant and has gradually taken market share... 

These first polyester fibers had melt transitions (T ) too low for use as textile fibers, and they were not investigated further. Carothers then turned his attention to the reactions of dicarboxylic acids and diamines to form polyamides and, in 1934, synthesized nylon 66, the first purely synthetic fiber. Nylon 66 is so named because it is synthesized from two different monomers, each containing six carbon atoms. 

Sulfur dyes are used mainly for dyeing textile ceUulosic materials or blends of ceUulosic fibers (qv) with synthetic fibers such as acryUc fibers, polyamides (nylons), and polyesters. They are also used for sHk (qv) and paper (qv) in limited quantities for specific appHcations. Solubilized sulfur dyes are used on certain types of leathers (qv). 

Nylon was the first commercial polymer to make a substantial impact on the textile industry, but polyesters now comprise the largest segment of the market for synthetic fibers. In fact, polyesters account for 40% of the more than 4 billion kilograms of synthetic fibers produced in the United States each year. The leading polyester, by far, is poly(ethylene terephthalate), or PET. This polymer is made from terephthalic acid and ethylene glycol in an acid -alcohol condensation reaction ... 

The first noncellulosic (synthetic) fiber to be of major importance for textile apparel was nylon. In the United States, nylon 66 was commercially produced in 1939 (4). Nylon 6, another polyamide which is produced also on a large scale, was obtained on a pilot plant scale in the same year in Germany (5). Modacrylic and acrylic fibers were commercially produced in the United States in 1949 and 1950, respectively (4). Polyester fiber was invented in England in 1940 (1) and went into commercial production in the United States in 1953 (4). Polyester production is higher than that of any other man-made fiber at this time (Table II). 

The world textile industry is one of the largest consumers of dyestuffs. An understanding of the chemistry of textile fibers is necessary to select an appropriate dye from each of the several dye classes so that the textile product requirements for proper shade, fastness, and economics are achieved. The properties of some of the more commercially important natural and synthetic fibers are briefly discussed in this section. The natural fibers may be from plant sources (such as cotton and flax), animal sources (such as wool and silk), or chemically modified natural materials (such as rayon and acetate fibers). The synthetic fibers include nylon, polyester, acrylics, polyolefins, and spindex. The various types of fiber along with the type of dye needed are summarized in Table 8.2. 

The major use of polymers has been as replacements for naturally occurring materials. Synthetic fibers such as nylon and polyester have substantially replaced natural textiles synthetic rubber is vastly superior to natural rubber, and the wide variety of engineering polymers (both thermosets and thermoplastics) have replaced traditional, naturally occurring materials such as metals and cellulosic compounds in many applications. 

The plastics industry and all the products made from plastics are almost entirely dependent on chemicals extracted or produced from hydrocarbons. This includes not only the familiar materials such as polyethylene, polypropylene, polyvinyl chloride (PVC), epoxies, nylon, polyesters, polycarbonate. Teflon and Plexiglas, but also includes a large portion of materials made from rubber and a diverse group of other materials formulated from polymers such as tape, glue, ink, waterproofing, wax, and polishes. Virtually all the synthetic fibers used in textile products, Orion , Dacron , Nylon and polyesters are made from polymers based on hydrocarbons. 

Vinyl polymers and condensation polymers were studied for the production of synthetic fiber. In 1932, Carothers and Hill of Du Pont studied linear aliphatic polyester and showed that fibers of sufficiently good mechanical properties are obtained by melt-spinning and colddrawing [8]. Polyester fiber was considered unsuitable as a commercial fiber because it has a low melting point and hydrolyzes easily with water. Carothers therefore turned his investigation from polyester to polyamide, and, in 1938, Du Pont announced the success of a new fiber called nylon. In Japan, studies to produce textile fibers from PVA began in 1938 and were intensively promoted. 

Polyolefins are increasingly becoming an integral part of the textile and nonwoven industries. Even though they have not historically enjoyed the same fame achieved by polyester and nylon in synthetic fiber applications, polyolefins offer... 

Textile fibers (cotton, silk, wool, hair, rayon, nylon, polyester, aramid, etc.) Structural materials (lumber, composites, poly(oxymethylene), PVC, nylon, etc.) Rastios (polyethylene, polypropylene, polytetrafluoroethylene, polyoxide, etc.) Adhesives (glues, epoxies, polyvinyl alcohol, synthetic rubber, segmented polyurethanes, etc.) Biological materials (the basic molecules, carbohydrates, proteins, and DNA)... 

Cleansing of materials (substrates) implies the removal of soil and stains. A wide variety of stains and substrates are encountered. For instance, textiles may be of natural origin such as cotton, wool, or natural silk, or are made of synthetic fibers, such as nylon, polyester, or polyacryl. Cotton is cellulose that has an intermediate hydrophobicity wool and natural silk are proteins, both rather hydrophobic and in most cases negatively charged. Synthetic fibers are usually polymers of which the backbone is characterized by a series of repeating units such as peptide units (in nylon), ester bonds (in polyesters), and cyan groups (in polyacryl). 

In certain cases, identifying the specific garment or textile product and the allergen it contains will be an important undertaking. The fiber content of the fabric will narrow the possible dyes, as certain dyes are used to color certain fibers. Cotton, rayon, and linen fabrics are dyed with direct, fiber-reactive, mordant, azoic, sulfur, and vat dyes. Wool fabrics are dyed with acid, mordant, and fiber-reactive dyes. Polyester fabrics are dyed with disperse dyes unless the polyester is modified to accept basic dyes. Nylon fabrics are colored with acid and disperse dyes unless modified to accept basic dyes. Acrylic fabrics are dyed with basic and disperse dyes. Acetate fabrics are dyed with disperse dyes. Other synthetic fibers are dyed with disperse dyes. 

Flexible linear macromolecules make up, as mentioned before, the newest class of molecules and are the molecules most important to man. Their number is practically unlimited. For examples, almost all textile fibers are flexible macromolecules, from cotton, silk, wool, hair, and rayon to nylon, polyesters, and aramid. Many structural materials are also flexible macromolecules, such as lumber, compmsites, polyoxyethylene, poly(vinyl chloride), and nylon. Because of the ease of melting, many flexible macromolecules have earned the name plastics, such as polyethylene, polypropylene, polytetra-fluoroethylene, and polyoxides. Many adhesives such as glues, epoxides, poly-(vinyl alcohol), cyanoacrylic polyesters, and ethylene-vinyl alcohol copolymers are based on flexible macromolecules. The unique combination of viscosity and elasticity in the liquid state makes many flexible macromolecules useful as elastomers, of which natural and synthetic robbers and segmented polyurethanes are best known. Class 2 also includes the biolo cal macromolecules carbohydrates, proteins, and DNA. The biological macromolecules alone are practically unlimited in number, as documented by the variety of forms of life. 

In the textile industry, yam spinning was one of the very first processes to be industrialized. Spun yams may contain a single type of fiber or a blend of various types. Combining synthetic fibers (which can have high strength, luster, and fire-retardant qualities) with natural fibers (which have good water absorbency and skin-comforting qualities) is very common. The most widely used blends are cotton-polyester and wool-acrylic fibers. Blends of different natural fibers are common too, especially with more expensive fibers such as cashmere. Yams are selected for different textile products based on the characteristics of the constituent fibers, such as wool for warmth, nylon for durability, cashmere for softness, etc. 

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