Chemical Interpretation of the Relaxed Permittivity during Epoxy Resin Cure

摘要

The change in dielectric constant during cure of a diglycidyl ether of bisphenol-A resin (EPON 825) with diamino diphenyl sulfone was studied using microdielectrometry and differential scanning calorimetry. The dipole moments attributable to the epoxide and amine groups were obtained by dielectric measurements on the starting materials, and on related model compounds whose functionality precludes crosslinking. The decrease of the relaxed dielectric constant, Epsilon sub r, during cure can be attributed to the consumption of the polar reactive groups by the crosslinking reaction, and can be correlated with the extent of conversion measured by DSC. The DSC rate data was fit to a kinetic model, and the model used to calculate concentrations of reactive groups versus time. The Frohlich theory, which relates the static dielectric constant to the concentrations and moments of dipoles in the material, was used to interpret the epsilon sub r curing behavior.