Polymers for use at High Temperatures

The bulk of plastics materials are required to operate within the range of -30 to + 100°C. There has, however, been a steadily increasing demand for materials to operate outside of these ranges, particularly in certain aerospace, military and telecommunications applications. A considerable amount of research work has been carried out in response to this demand and many thousands of polymers, both organic and inorganic, have been prepared. Many of those which have achieved commercial use have been considered in earlier chapters but in the final part of this chapter it is intended to review the overall situation. 

Polymers for use at high temperatures fall into two groups  

The range of high-temperature rubbers is very small and limited to the silicones, already considered in this chapter, and certain fluororubbers. With both classes it is possible to produce polymers with lower interchain attraction and high backbone flexibility and at the same time produce polymers in which all the bonds have high dissociation energies and good resistance to oxidation. 

In the case of the high-temperature high-Tg plastics the two main requirements are that  

In certain cases resistance to hydrolysis and solvents (particularly oils) may also be required. 

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In Table 15.3 are shown the chemical structures and Tg and of some representative thermoplastic polymers for use at high temperature (3,9). These matrices have high continuous service temperatures (120-200° C) even under wet environmental conditions. Advantages of thermoplastic over thermoset matrices are their shorter fabrication cycle (generally controlled environment storage is not required) and the possibility to be reprocessed and reconsolidated after manufacture. Poly(ether ether ketone) is a strong contender with epoxy resins for use as a matrix in composite prepregs with carbon fibers to be utilized in structural aircraft components. 

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