Comparison of dielectric properties between epoxy composites with nanosized clay fillers modified by primary amine and tertiary amine

Epoxy-based nanocomposites (NCs) were prepared using clay modified by either primary amine or tertiary amine, and the effect of the difference in modifier on the thermal and dielectric properties of the NCs were discussed. The NC with clay fillers modified by the primary amine, 1C, shows a glass transition end temperature (T
_eg
) at a temperature 20°C lower than the neat epoxy (N). This indicates that the resin of 1C is less crosslinked than that of N. On the other hand, the sample 3C, in which the clay was modified by the tertiary amine, shows a DSC spectrum close to that of N. Namely, 3C has a high crosslinking density similar to N. While the three samples show a relaxation peak in their dielectric loss spectra, the peak appears at high frequencies in 1C compared to N and 3C. Moreover, ionic conduction current flows more at high temperatures in 1C than in N or 3C. These facts are ascribable to the difference in their crosslinking densities.