Dielectric Study of Epoxy Vitrification: Does a Percolation Model Apply?

Dielectric measurements were performed during the cross-linking reaction of an epoxy/amine system. Two transitions are successively crossed: the gelation which is a transition of connectivity and the vitrification which is a transition of mobility. It is found that dielectric measurements are insensitive to gelation but nevertheless are a powerful method of investigation for the vitrification process. This latter transition is interpreted as a percolation of growing vitreous domains.