Poly ether ketone s, PEKs

In contrast to PES s, PEK s are crystaHine engineering plastics having melting temperatures in the range of 320-420 °C. The tendency to crystallize is based on the fact that bond angles and steric demands of ether and keto group are quite similar. 

Furthermore, unsubstituted para-linked benzene rings are required as building blocks. Whereas the chemical and thermal stabilities are quite similar to those of PES s, the crystallinity results in higher heat-deflection temperatures. However, PEK s are sensitive to UV light like all aromatic ketones. Carbon-fiber reinforced PEEK can rival with steel in terms of stiffness, toughness, and elastic modulus at a significantly lower weight. Further information on syntheses, modification, properties, and applications are available from review articles [98, 107-109]. 

Anton A, Baird BR (2003) Polyamide, fibers. In Mark H (ed) Encyclopedia of polymer science and technology, vol 3, 3rd edn. J. Wiley Sons, Hoboken, p 584 

Kohan MI (1995) Nylon plastics handbook. Hanser Verlag, Munchen 

---

Depending on the number of ether and keto groups in the constitutional repeating units one distinguishes between poly(ether ketone)s (PEK, x = y = 1), poly(ether ether ketone)s (PEEK, x = 2, y = 1), poly(ether ketone ketone)s (PEKK, X = 1, y = 2), and poly(ether ether ketone ketone)s (PEEKK, x = y = 2). 

Monomers for poly(ether ether ketone)s (PEEK)s and poly(ether ketone)s (PEK)s are shown in Table 6.1. Varieties of PEEK are shown in Figure 6.2. PEEK-WC is poly(oxa-p-phenylene-3,3-phthalido-p-phenylene-oxa-p-phenylene-oxy-phenylene). In addition to PEEK, the carbonyl group is partly modified with phthalide units. It is an amorphous PEEK. 

Similarly to poly(ether ketone)s (PEK)s, PENs have been prepared according to a nucleophilic route and an electrophilic route. 

FIGURE 5.3 Synthesis of postsulfonation poly(ether ketone)s (PEKs) using (a) chlorosul-fonic acid and (b) fuming sulfuric acid. 

PEKEKK. See Poly(arylene ether ketone ether ketone ketone) (PEKEKK) PEKK copolymer, alternating, 334 PEKs. See Poly(arylene ether ketone)s (PEKs)... 

Acyl cations are involved as propagating species in the synthesis of poly-(ether ketone)s. Poly (ether ketone)s are a class of thermoplastic crystalline polymers that have many desirable properties that make them useful as high-performance engineering materials [153,154]. The poly(ether ke-tone)s with the most useful properties are actually para-linked poly(aryl-ether ketone)s (PAEKs). They have excellent chemical resistance to oxidation and hydrolysis, high thermal stability, and many useful mechanical properties. Unlike some other materials with similar properties they are readily melt processable using conventional equipment. In addition, their mechanical properties are not affected deleteriously by most solvents. These polymers are usually crystalline. PAEKs contain arene groups joined by ether and carbonyl linkages. For example, two commercial poly-(ether ketone)s are PEK and PEEK (Fig. 36). 

The electrophilic route for the production of aromatic poly(ether ketone)s involves the use of Friedel-Crafts catalysts. AICI3 is used as a catalyst for the polymerization of /p-phenoxybenzoyl chloride as such, or p-phenoxybenzoyl chloride or terephthaloyl chloride and 1,4-diphenoxybenzene to give a PEK. A PEEK is obtained by the use of / -phenoxyphenoxybenzoyl chloride, respectively [8]. The process is carried out at low temperatures, such as 0-30 °C. Due to the heterogeneous nature of this reaction, generally undesirable lower molecular weight polymers are produced. 

Figure 17. Room-temperature proton conductivity of two Dow membranes of different EW values, Nation, two varieties of sulfonated poly (ary lene ether ketone) s (S— PEK and S—PEEKK, unpublished data from the laboratory of one of the authors), and sulfonated poly(phenoxyphos-phazene)s (S—POPs °9 of different equivalent weights (685 and 833 g/equiv), as a function of the degree of hydration n = [H20]/I—SO3H] (number below the compound acronym/ name indicates the EW value).

Poly(aryl ether ketone)s are thermostable polymers in which ether (E) and ketone (K) units connect phenylene rings, giving a range of polymers of the types PEK, PEEK, PEKEKK, etc, (Fig, 4,3), The proton conductivity, thermal, and mechanical properties of sulfonated PEEK [16,17], and its fuel cell performance in hydrogen-air and hydrogen-oxygen up to 110°C [17], as well as in DMEC, have been reported in recent years, and long-term tests have claimed lifetimes of up to 4,300 h at 50°C [18],... 

Figure 18 shows the temperature dependence of the proton conductivity of Nafion and one variety of a sulfonated poly(arylene ether ketone) (unpublished data from the laboratory of one of the authors). The transport properties of the two materials are typical for these classes of membrane materials, based on perfluorinated and hydrocarbon polymers. This is clear from a compilation of Do, Ch 20, and q data for a variety of membrane materials, including Dow membranes of different equivalent weights, Nafion/Si02 composites ° ° (including unpublished data from the laboratory of one of the authors), cross-linked poly ary lenes, and sulfonated poly-(phenoxyphosphazenes) (Figure 19). The data points all center around the curves for Nafion and S—PEK, indicating essentially universal transport behavior for the two classes of membrane materials (only for S—POP are the transport coefficients somewhat lower, suggesting a more reduced percolation in this particular material). This correlation is also true for the electro-osmotic drag coefficients 7 20 and Amcoh...

---