Revealing defects hampering the formation of epoxy networks with extremely high thermal properties: Theory and experiments

Abstract

We present a combined experimental and theoretical investigation of thermal properties of cycloaliphatic epoxy networks. The networks are prepared from 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate ERL-4221 as a monomer and 4-methylhexahydrophthalic anhydride as a curing agent and their glass transition temperature Tg is evaluated by dynamic mechanical and thermal mechanical analyses as well as by differential scanning calorimetry. It is found that the cured epoxy networks have high Tg values reaching 233–238 °C. The method of anharmonic oscillators is first proposed to simulate the effect of network structure on the thermal properties. It suggests that further increase of Tg values is not attained because of the formation of intramolecular cyclic structures. Studies of model reaction by mass-spectrometry confirm the formation of such structures at curing.