PHYSICAL AGING STUDIES OF POLYSILOXANE-MODIFIED EPOXY-RESIN

Epoxy network systems were prepared based on diglycidyl ether of bisph enol A with two kinds of low molecular weight polysiloxane, aminopropy ldimethyl-terminated polysiloxane and phenyl-terminated polysiloxane. Their physical ageing phenomena were studied by differential scanning calorimetry. The calorimetric data obtained after annealing the neat a nd the modified cured epoxy resins at 175 degrees C show that two kind s of relaxation-internal stress relaxation and enthalpy relaxation-tak e place simultaneously during annealing. Furthermore, the extent and t he rate of relaxation are closely related to the kind of modifiers and their ratio.