The β relaxation of a phenoxy resin and a number of related uncured and cured bisphenol‐type epoxide resins was studied using a torsion pendulum. Two molecular mechanisms are proposed to contribute to the β relaxation in the range from −55 to −80°C. One is the motion of the hydroxyether group and the other is related to motions of the crosslink itself. The β‐relaxation peak temperature was found to increase with the concentration of hydroxyether groups in the matrix. Motion of the crosslinks in the matrix gives rise to a contribution to the β peak at −80°C. In addition, motion of the diphenyl propane group is proposed to result in a relaxation process at ca. −110°C.
Static and dynamic mechanical properties of cured epoxide resins based on ester bonds, ether bonds, or a mixture of ester and ether bonds were investigated. Their network structures were estimated from the results of gel content before and after saponification, and conversion of functional groups. It was found that cured epoxide resins based on a mixture of ester and ether bonds indicate intermediate properties between the resins based on ester bonds and the resins based on ether bonds. Both dynamic and static mechanical properties were strongly affected by their network density and their segmental structures suggested in this paper.
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