The β relaxation behavior of bisphenol‐type resins

Abstract

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.

Effect of resin modifiers on the structural properties of epoxy resins

“…who mention an increase of the β‐transition amplitude and a shift to higher temperatures with admixed diluent, in their case DGEBD . In other studies, a correlation of the intensity of the β‐transition and the crosslink density of a system was described . Higher crosslinked systems revealed higher peak amplitudes and temperatures.…”

“…11 In other studies, a correlation of the intensity of the b-transition and the crosslink density of a system was described. 10,11,18,39,40 Higher crosslinked systems revealed higher peak amplitudes and temperatures. The investigated resins in this work exhibited higher crosslink density with increasing amount of modifier.…”

A discussion of the molecular mechanisms of moisture transport in epoxy resins

“…However, anhydride-cured resins, such as the non-amine resins, also exhibit a ␤-relaxation onset similar to the amine-containing resins. 12,13 Such an observation appears at odds with ascribing the transport kinetics to the local-scale motions of the ␤ process. To resolve this apparent contradiction, one must consider the role of polarity.…”

Mechanical properties of epoxy networks based on DGEBA and aliphatic amines

“…These results are indicating that some relaxation mechanisms due to hydroxy ether, 30,32,34 diphenyl propane 32 and crosslinking 35 are operating in some extent but in a complex way. In Figure 6 the smooth curves seem to indicate that the three possible groups contributions are coupled.…”