High-strength synthetic fibers

Dragline silk, used by spiders... exhibits a combination of strength and toughness unmatched by other high-performance synthetic fibers. [Kevlar]... 

Whereas natural fibers, mainly in the form of short fibers and fabric chips, have foimd application above all in the curable phenoplast and aminoplast molding compounds, it was more than anything else the development of the polyesters and epoxy resins that made it necessary to develop new kinds of reinforcing fibers to optimize the properties of these products as well. Modem, high-strength, synthetic organic fibers are the results of these efforts [112]. 

Z. Feng, B. Ranby, Photoinitiated surface grafting of synthetic fibers. 1. Photoinitiated surface grafting of ultra-high strength polyethylene fibers. Ange-wandte Makromolekulare Chemie 195 (1992) 17. 

Figure 4.1 represents the chemical structures of para-linked, poly(p-phenylene terephthalamide) (PPPT) and meta-linked, poly(m-phenylene isoph-thalamide) (PMPI) aromatic polyamides. These commercial aramids can be transformed into flame, cut-resistant, and high-tensile-strength synthetic fibers, which are widely used in the field of coatings. 

The use of 2-aminothiazole derivatives as dyeing compounds is direct related to the development of synthetic fibers. Some typical examples are given in Table VI-14. The importance of these dyes lies in their performance on acetate fibers. They have excellent fastness to gas fumes, produce a bright blue shade, and have a high tinctorial strength. Their only disadvantage is their relatively low light fastness, which does limit their application. 

Synthetic polymers have become extremely important as materials over the past 50 years and have replaced other materials because they possess high strength-to-weight ratios, easy processabiUty, and other desirable features. Used in appHcations previously dominated by metals, ceramics, and natural fibers, polymers make up much of the sales in the automotive, durables, and clothing markets. In these appHcations, polymers possess desired attributes, often at a much lower cost than the materials they replace. The emphasis in research has shifted from developing new synthetic macromolecules toward preparation of cost-effective multicomponent systems (ie, copolymers, polymer blends, and composites) rather than preparation of new and frequendy more expensive homopolymers. These multicomponent systems can be "tuned" to achieve the desired properties (within limits, of course) much easier than through the total synthesis of new macromolecules. 

Fibers in which the basic chemical units have been formed by chemical synthesis, followed by fiber formation, are called synthetic fibers. Examples include nylon, carbon, boron fibers, organic fibers, ceramic fibers, and metallic fibers. Among all commercially available fibers, Kevlar fibers exhibit high strength and modulus. (Kevlar is a DuPont trademark for poly [p-phenylene diamine terephthalamide].) It is an aromatic polyamide (aramid) in which at least 85% of the... 

---