| Abstract: | Similar thermal expansion instabilities, consisting of isothermal, time-dependent changes in thermal expansion after a rapid change in temperature, were observed in epoxy resins with different degrees of cross-linking. Creep experiments performed at different stages of expansion show decreases in tensile creep rate with decreased expansion. The role of changes in moisture content as a possible cause of the dimensional instability is examined for epoxy resins and a highly cross-linked polyurethane. Results indicate that the state of expansion is the primary cause of changes in creep rate rather than temperature or moisture content. |
