Microwave radiation curing of polymers: Using a temperature equivalent method for cure reaction analysis

Abstract

Microwave curing has been shown to be a viable alternative to conventional thermal curing of polymers on the basis of significant reaction rate enhancements. Proper understanding of the microwave cure reaction kinetics has been hindered by the lack of an adequate basis relating the process to conventional thermal analysis methods. The rate enhancement obtained in microwave curing is shown to have been obtained from the decrease in the lag time prior to initiation of cross-linking, as well as, a decrease in the effective cure time. Phenomenologically, the shortening of the cure time is no different from a shortening achieved by a higher curing temperature, thereby providing a basis for relating the microwave cure process to thermal curing. This article attempts to relate the test results for both thermal and microwave curing by obtaining a temperature equivalent value using a phenomenological logarithmic approach. Results show that the equivalent temperature can be elucidated using a logarithmic plot of the cure times and the glass transition temperature. The values of the equivalent temperature so obtained were also consistently and significantly higher than the actual sample temperature during cure, confirming microwave curing to differ in mechanism from thermal curing. © 2000 John Wiley & Sons, Inc. Adv Polym Techn 19: 194–202, 2000