High-performance polymers properties

The value of many chemical products, from pesticides to pharmaceuticals to high performance polymers, is based on unique properties of a particular isomer from which the product is ultimately derived. Eor example, trisubstituted aromatics may have as many as 10 possible geometric isomers whose ratio ia the mixture is determined by equiHbrium. Often the purity requirement for the desired product iacludes an upper limit on the content of one or more of the other isomers. This separation problem is a compHcated one, but one ia which adsorptive separation processes offer the greatest chances for success. 

Although urushiol possesses an interesting structure for transformation into speciality polymers, no attempt has been reported. Notwithstanding its applications in a specified area, it appears that it is not properly put to use as it can be converted to polymers with better properties. The possibilities for such conversions into high-performance polymers are illustrated by cardanol, a phenolic lipid of related structure obtained from Ana-cardium occidentale. 

Polyesters are one of the most versatile classes of polymers ever produced, covering a wide range of properties and applications. Polyesters are present in fibers, engineering thermoplastics, and high-performance polymers as well as in thermosetting resins and elastomers. Table 2.1 lists the chemical structure, abbreviations, and uses of some commercially important thermoplastic polyesters. 

A variety of polymer compositions that use this type of polymerization chemistry can be envisioned. In addition to the polyarylate homopolymers that have been described in this chapter, random or block copolymers can be prepared with reasonable ease by the combination of different monomers or oligomers. These compositions can be designed to optimize thermal, mechanical, dielectric, or optical properties of a polymer system. Also, the trifluorovinyl ether functionality can be incorporated into other high-performance polymer systems with relative ease.34,35 The perfluorocyclobutane polyarylate chemistry is a versatile approach to the preparation of high-performance polymers, which is just beginning to demonstrate its utility. 

Sulfonated poly(arylene ether)s have shown promise for durability in fuel cell systems, while poly-(styrene)- and poly(imide)-based systems serve as model systems for studying structure-relationship properties in PEMs because their questionable oxidative or hydrolytic stability limits their potential application in real fuel cell systems. Sulfonated high performance polymer backbones, such as poly(phe-nylquinoxaline), poly(phthalazinone ether ketone)s, polybenzimidazole, and other aromatic or heteroaromatic systems, have many of the advantages of poly-(imides) and poly(arylene ether sulfone)s and may offer another route to advanced PEMs. These high performance backbones would increase the hydrated Tg of PEMs while not being as hydrolytically sensitive as poly(imides). The synthetic schemes for these more exotic macromolecules are not as well-known, but the interest in novel PEMs will surely spur developments in this area. 

Several high-performance or engineering polymers, such as the polyfluo-rocarbons, acetals, ABS, nylons, polyurethanes (PUs), silicones, and phos-phazenes, have been described in previous chapters. Several elastomers, such as butyl rubber, EPDM (elastomeric terpolymer from ethylene, propylene, and a nonconjugated diene), and Neoprene, which play a vital role in engineering, and a host of classic thermosets should also be considered high-performance polymers. The properties of other high-performance polymers are described in this chapter. 

High-performance polymers, such as polyphenylene sulfide (PPS) (Ry-ton), have excellent resistance to elevated temperatures, and this property can be enhanced by the incorporation of reinforcing fibers such as graphite fibers. 

Tiie value of many chemical products from pesticides to pharmaceuticals to high performance polymers, is based on unique properties of a particular isomer from whicli the product is ultimately derived. Often the purity requirement for the desired product includes an upper limit on the content of... 

Polysulphone (PSU) is a high-performance polymer with superior mechanical, electrical and thermal properties in a temperature region from -100 up to 180 °C. It is mainly used in exacting mechanical and electrical applications. 

Polyether ether ketone (PEEK) and Polyether sulphone (PES) belong to the most recent developments in the field of technical high-performance polymers. Both possess very good thermal and mechanical properties, which can be further improved by reinforcing fibres. Their application is mainly in aircraft and space vehicles. 

Morphology control in a mixing operation is, therefore, very important for utilizing the properties of a blended-in high-performance polymer. It appears that continuity of one or both phases is often essential to obtain optimum properties. This continuity is generated in the blending process, though, unfortunately, not much is known of the ways to control it. 

Furukawa N, Yamada Y, Kimura Y (1996) Preparation and stress relaxation properties of thermoplastic polysiloxane block polyimides. High Perform Polym 8(4) 617... 

Yamada Y, Furukawa N, Tujita Y (1997) Structure and gas separation properties of silicone-containing polyimides. High Perform Polym 9(2) 145... 

A miscible polymer—polymer blend almost always yields a physical- property spectrum superior to the individual components, and this allows the development of a new set of products with significant savings in capital investment. Partly for this reason and partly because new and commercially viable polymers are becoming harder to come by/ the plastic industry has expended a sizeable sum towards identifying miscible high-performance polymer mixtures. Indeed, the more recent renewed experimental and theoretical programs have resulted in an increased number of known miscible blends. On the commercial scene, however, successful miscible polymer-polymer blends are still rather few and are limited to... 

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