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.