In situ real-time study of crosslinking kinetics in thermal and microwave fields

Abstract

A comparative investigation has been conducted of the mechanisms and rate of chemical reactions in thermal and microwave fields. A number of nonpolymer-forming and polymer-forming mixtures of different functionality and molecular architecture were prepared and investigated. The advancement of reactions in thermal and microwave fields was monitored in real time by in situ remote near-infrared spectroscopy. The principal finding was that the use of microwaves in lieu of thermal heating had no effect on the mechanism or kinetics during the isothermal cure of various epoxies, polyimides and bismaleimides. No "microwave effect" was observed and it was concluded that the claims of "accelerated kinetics" in the microwave field are unfounded. However, a comparison between thermal and microwave cure assumes a whole new dimension when the temperature distribution inside the sample is considered, and that constitutes a scientifically challenging area that warrants further research. © 1998 John Wiley & Sons, Ltd.