High Performance Polymers 5 Thermosets

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. 

Thermosets or highly crosslinked polymers give high char yields. Similarly, many high performance polymers, e.g., PEEK, PES, polyethe-rimide (PEI), not only have high LOI values but also tend to decompose to a char. 

In the late 1970s, Kirchhoff at Dow Chemical Company developed the use of benzocyclobutenes in polymer synthesis and modification. These efforts culminated in 1985 with the issuance of the first patent describing the use of benzocyclobutene in the synthesis of high-molecular-weight polymer.27 Similar work that involved a thermosetting system based on Diels-Alder cycloaddition between terminal benzocyclobutene and alkyne groups,28,29 was reported separately and independently by Tan and Arnold.28 Since these initial discoveries, the field of benzocyclobutene polymers has expanded rapidly and benzocyclobutene chemistry constitutes the basis of a new and versatile approach to the synthesis of high-performance polymers for applications in the electronics and aerospace industries.30... 

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. 

In spite of their utility and versatility, the new high performance polymers will not displace general purpose thermoplastics, classic thermosets, ceramics or metals unless there is a demonstratable superiority. Fortunately, there are many applications for high performance thermoplastics for which no other material is adequate. Hence, the annual production of high performance thermoplastics in the late 1980 s will exceed the production of all plastics in the 1940 s. This unprecedented growth of these engineering polymers will be based entirely on their performance. 

Riccardi et al. (1996) focussed on the modelling of phase separation in reactive thermoset-solvent-high-performance-polymer mixtures by characterizing the interaction parameter as a function of conversion in a thermodynamic model. The reaction-induced... 

Quasi-Static Loading of Thermosets and High Performance Composites - Data I Polymer Solids and Polymer Melts R. Lack, W. Grellmann 5.2.1 Quasi-Static Loading Table 5.15 Fracture toughness Ki of thermosets and high performance polymers at quasi-static loading (RT - room temperature 20 - 25 °C). ... 

Abu Abu-Shanab, O. L., Chang, C. P., Soucek, M. D. Polyphosphazene toughened PMR-type thermosets. High Perform. Polym. 8 (19%) 455 73. 

Table 5.16 Energy-determined parameters Gi or /ic ( ) of thermosets and high performance polymers at ...

Nunoshige J, Akahoshi H, Ueda M. Molecular weight control of thermosetting poly(phenylene ether) copolymer produced by heterogeneous oxidative coupling polymerization. High Perform Polym 2010 22(4) 458-67. 

Chiefari J, Dao B, Groth AM, Hodgkin JH. Water as solvent in polyimide synthesis thermoset and thermoplastic examples. High Perform Polym 2003 15(3) 269-79. 

Polyesters are a very important class of high performance polymers, which find extensive use in a number of diverse appHcations [19], Unsaturated polyester resins was chosen in the present study for making fiber-reinforced composites because of their good strength and low cost in comparison to other thermosetting resins. 

Synthetic thermosetting polymers used in the construction industry are polyester, vinylester and epoxies these materials are generally used to manufacture parts of the machines that produce sustainable energy generators. In addition, thermoplastic resins, such as polyetheretherketone (PEEK), polyethersulphone (PES) and various liquid crystal polymers (LCP) are also used. The latter high performance polymers also meet stringent out-gassing (relevant to space environments) and flammability requirements. 

Thermosets may be omitted In some lists of high performance polymers but they meet specifications and would not be used today If they were not high performance material. This criterion applies to carbon fibers, barrier resins, thermotropic polyesters, interpenetrating network polymers and many specialty elastomers. Likewise, the introduction of UV/EB curing techniques has brought about a new era in the polymer industry. 

LCP are fully aromatic copolyesters or copolyesteramides which have become the standard high performance polymers used in certain new electrical/electronic applications notably fuel cells. Thermosetting LCP are also available. 

Balamumgan R, Kannan P (2009) Synthesis and properties of a liquid crystalline thermoset epoxy resin containing 1,3,4-oxadiazole groups. High Perform Polym 21 251-264... 

A list of materials regarded as high-performance polymers (Table 17.10) overlaps the list of Table 17.9 to some extent, but also includes thermosets such as epoxy, phenolic, and silicone molding resins. As with most molded plastics, high-tanperature performance is enhanced by reinforcement with glass, boron, or carbon or aramid fibers. The thermosets are seldom used without reinforcement. Several are inclnded in Figures 17.6 and 17.7. 

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