THE KINETICS OF VOLUME RELAXATION AND RELATED PROPERTY CHANGES DURINGPHYSICAL AGING OF POLY(ETHER ETHER KETONE) (PEEK)

Structural relaxation is accompanied by a simultaneous change in all s tructure-sensitive physical mechanical properties. Naturally, a fundam ental correlation between structural relaxation and the variation of t he properties of the glass would be of great interest to scientists an d engineers. Changes in mechanical and dielectric properties during th e course of structural relaxation are of particular interest, but one must remember that their measurements involve the use of external stre ss (or strain), which, regardless of its magnitude, will affect the on going structural relaxation. The application of even the smallest stre ss or strain could shorten the relaxation time by one or more orders o f magnitude and hence caution must be exerted in seeking correlations between volume and enthalpy relaxation on the one hand, and viscoelast ic (mechanical or dielectric) measurements on the other. The two appro aches can be viewed as manifestations of the same structural relaxatio n although one must bear in mind that they differ fundamentally in ter ms of the cause and the effect, and while the theoretical background o f correlation between structural and viscoelastic relaxation has not b een explored, in this paper an empirical correlation between the two w ill be reported.