Relation Between the Glass Transition and Dielectric Properties in Bisphenol A and F Epoxy Resins

Bisphenol A and F epoxy resins, EA and EF for short respectively, are used widely for insulation in power apparatus. In this paper, we compare the superiority in dielectric property between EA and EF. For EA and EF cured at two different conditions, the glass transition temperature (T
_g
), complex relative permittivity (ε
_r
' - jε
_r
"), conductivity (σ), thermally stimulated depolarization current (TSDC), and bending elastic modulus were measured. As a result, EF has a lower T
_g
than EA. Regarding this, in EF, ε
_r
', ε
_r
", and σ rapidly increase when the temperature exceeds 140 °C and the difference in dielectric property between EA and EF becomes significant in this temperature range.