Digital image correlation measurement of resin chemical and thermal shrinkage after gelation

Abstract

A method for measuring chemical shrinkage and coefficient of thermal expansion during cure and post-gelation is presented based on digital image correlation to record the in situ stress-free strain field in a thermosetting polymer. An independent determination of the resin cure kinetics was required to relate the chemical shrinkage strain and coefficient of thermal expansion to the degree of cure. The changes in the coefficient of thermal expansion were observed from the initial heating to final cooling of the sample. The results obtained are shown to compare favorably with results previously found by other techniques. The proposed method provides a simple and reliable procedure to measure the evolution of thermo-chemical shrinkage properties of the resin during the cure cycle.