Other Advanced Fibers

One class of HMHS fibers has not been mentioned liquid-crystalline polyesters, thermotropic polymers, melt-spun. In the 1970s and 1980s many compositions were studied, in most cases fully aromatic polyesters, in one case PET enriched with large quantities of p-hydroxybenzoic acid (pHBA). Only one product sur- 

Fiber Density [gcnr ] Elongation [%] Tenacity [N tex- ] [CPa] Modulus [N tex ] [CPa] 

There are many polymers with high-temperature resistant fibers, most of them with textile properties (low tenacity, high elongation) (see Table 17.7). Their application is in insulation, hot gas filtration, and suchlike. Large products are meta-meta aramid (Nomex, Teijin-Conex) and polybenzimidazole (PBI). Smaller products are poly(phenylene sulfide) (PPS), several aromatic polyketones (for example poly(ether ether ketone), PEEK) and aromatic polysulfones see Reference 9, Chapters 8 and 9. 

HMHS high-modulus, high-strength fibers  

HSSDW high-speed spin-draw w inding  

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Of a large number of possible fluorinated acrylates, the homopolymers and copolymers of fluoroalkyl acrylates and methacrylates are the most suitable for practical applications. They are used in the manufacture of plastic lightguides (optical fibers) resists water-, oil-, and dirt-repellent coatings and other advanced applications [14]. Several rather complex methods to prepare the a-fluoroalkyl monomers (e.g., a-phenyl fluoroacrylates, a-(trifluoromethyl) acrylic and its esters, esters of perfluoromethacrylic acid) exist and are discussed in some detail in [14]. Generally, a-fluoroacrylates polymerize more readily than corresponding nonfluorinated acrylates and methacrylates, mostly by free radical mechanism [15], Copolymerization of fluoroacrylates has been carried out in bulk, solution, or emulsion initiated with peroxides, azobisisobutyronitrile, or y-irradiation [16]. Fluoroalkyl methacrylates and acrylates also polymerize by anionic mechanism, but the polymerization rates are considerably slower than those of radical polymerization [17]. 

Although advanced fibers and composites offer tremendous potential value to the marketplace, historically fiber manufacturers have not realized enough profits to justify their investments. This has resulted in difficulty in maintaining a reliable fiber supply. In the absence of outside support, fiber manufacturers will continue to lose money until a viable market for CMCs develops. Because they cannot control how the market develops, however, they are in a more tenuous business position than other CMC stakeholders. 

In other advanced SILMs technologies, though not essentially SILMs in themselves, they used a solid microporous barrier to separate the aqueous phase from the organic one. Including in this concept are the nondispersive solvent extraction (NDSX) and pseudo-emulsion-based hollow-fiber strip dispersion (PEHFSD). 

Our previous papers [15,16] and the current work show that die imprinting of mesophase pitch particles with colloidal silica is an efficient technique to prepare mesoporous carbons with uniform spherical pores as well as carbons with bimodal pore size distributions. These carbons exhibit negligible amount of micropores, which can be further eliminated during graphitization process. If micropores are need, they can be created by controlled oxidation analogous to that used in the preparation of activated carbon fibers. The possibility of tailoring the size of uniform spherical mesopores is of great importance for catalysis, adsorption and other advanced applications such as die manufacture of hi -quaiity electrochemical double-layer capacitors, fuel cells and lidiium batteries. 

Polymers reinforced with cellulose fibers have received much attention in recent years because of their low density, nonabrasive, combustible, nontoxic, low cost and biodegradable properties. Several authors have reviewed recent advances in the use of natural fibers in composites like flax [ 1 ], jute [2,3], straw [4], kenaf [5,6], coir [7-9], fique [10], among others. Natural fibers have been used to reinforce thermoplastics and thermosets polymers in automotive and aerospace applications [11]. The influence of surface treatments of natural fibers on interfadal characteristics was also studied [12-17], and Joshi et al. [18] compared the life-cycle environmental performance of natural fiber composites with glass fiber composites. In this study, natural fiber composites were found to be environmentally superior in most applications. 

M. Mochizuki, M. Hirami, Biodegradable fibers made from truly-biodegradable thermoplastics, in P. N. Prasad, E. Mark, T. J. Fai (Eds.), Polymers and Other Advanced Materials, Plenum Press, New York, 1997, pp. 589-596. 

Germanium is an important semiconductor material. The development of the germanium transistor opened the door to countless applications in solid-state electronics. Today silicon has taken over the role as the main transistor element but germanium is very much used in other advanced appHcations, such as for instance fiber optics and solar cells. 

Starting from plain cotton-based products, medical textiles have seen rapid development over the last few decades. Nowadays, new biodegradable fibers have enabled the development of novel types of implants, and modem textile machines can produce three-dimensional spacer fabrics that give superior performance over traditional textile materials. These and many other advances have made medical textiles an essential element in modem disease management, and they are becoming more and more important with the increasing number of elderly people in the populations of developed countries. 

Advanced composites and fiber-reinforced materials are used in sailcloth, speedboat, and other types of boat components, and leisure and commercial fishing gear. A ram id and polyethylene fibers are currentiy used in conveyer belts to collect valuable offshore minerals such as cobalt, uranium, and manganese. Constmction of oil-adsorbing fences made of high performance fabrics is being evaluated in Japan as well as the constmction of other pollution control textile materials for maritime use. For most marine uses, the textile materials must be resistant to biodeterioration and to a variety of aqueous pollutants and environmental conditions. 

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