Modeling of Viscoelastic Behavior of an Epoxy Molding Compound During and After Curing

The generalized Maxwell model and Williams-Ladel-Ferry (WLF) equation of epoxy molding compound (EMC) under different temperatures were first identified. Via measuring the loss and storage moduli of the specimens under different curing conditions, an equation relating the degree of cure to the relaxation modulus, called the cure shift factor (a
_C
), was obtained. Considered with the WLF equation, which defines the temperature shift factor (a
_T
), the total shift factor was proposed as the product of a
_T
and a
_C
. With this dualistic shift factor, the relaxation modulus of EMC under any degree of cure coupling with different temperatures could be defined.