The β relaxation behavior of bisphenol‐type resins

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.