RELAXATION PROPERTIES OF A LINEAR EPOXY P OLYMER

A linear epoxy polymer based on the ED-22 oligomer and azelaic acid wa s synthesized (M = 6400, T(g) = 26-degrees-C). Relaxation transitions in the linear polymer (examined by mechanical and structural relaxatio n techniques) were compared with the relaxation transitions in a stron gly cross-linked epoxy polymer based on ED-22 and methyltetrahydrophth alic anhydride (M = 400, T(g) = 100-degrees-C). Small-scale transition s associated with various modes of intramolecular rotational motion we re described by the same transition temperatures and corresponding rel axation constants both for the cross-linked and the linear polymers. A n essential difference between the relaxation transitions was observed for the lambda-transition (glass transition) and, to a certain extent , for the lambda-transitions, which are related to the dissociation of the microvolume physical junctions of the molecular network. These di fferences are associated with two factors i.e., topological (chemical network) and intermolecular (density of the cross-linked polymer is hi gher than that of the linear polymer) factors. Chemical relaxation pro cesses, which are related to the dissociation of weak chemical bonds ( C-C and C-O) in the cross-linked polymer, were described by somewhat h igher activation energies.