Changes in Molecular Dynamics during Bulk Polymerization of an Epoxide−Amine System As Studied by Dielectric Relaxation Spectroscopy

Dielectric relaxation spectroscopy (DRS) and differential scanning calorimetry (DSC) have been used simultaneously as a means of following the isothermal cure of the diglycidyl ether of Bisphenol A with 4,4‘-diaminodicyclohexylmethane in the temperature range 290−353 K. The dielectric permittivity and dielectric loss of the thermosetting mixture have been measured as a function of reaction time over the frequency range 101.2−105 Hz. The evolution of the dielectric properties was studied as the curing temperature was lowered to values close to the solidification of a sample. The kinetics of the cure have also been determined, using calorimetry, for four reaction temperatures over the whole range of conversion up to the point where the system vitrifies and the reaction becomes diffusion-controlled. Correlations between the changes in molecular dynamics and the chemical kinetics occurring during the thermosetting process have been made in some detail, and a theoretical working model has been developed that allows DRS to predict the course of the reaction in the vitrification range. Previous interpretations of dielectric events in this vitrification region, based on experimental kinetic and dielectric results, are reexamined.