Electrical and mechanical properties of anhydride‐cured epoxy resins

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Abstract
A diglycidyl ether of bisphenol A was crosslinked with several acid anhydrides of different structures, such as the homologs of succinic anhydride and the acid anhydrides with a double bond or a ring structure. Dilatometric, dielectric, and dynamic mechanical measurements were carried out on the cured resins. The glass transition temperature is shown to be influenced by the presence of double bonds or ring structures in the chain backbones. The specific volume at the glass transition temperature can be predicted as a sum of atomic volumes. Two dielectric relaxation processes were observed in all the resins. The temperature dependence of the relaxation time for the α‐process can be represented by the WLF equation. The mechanical retardation time for the α‐process generally agrees with the dielectric relaxation time. The observed dynamic Young's modulus in the glassy state is nearly one‐third of the value calculated from the cohesive heat density. A good correspondence is obtained between the observed dynamic Young's modulus in the rubbery state and the Young's modulus calculated from the crosslinking density, but the deviation increases with decreasing crosslinking density.
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