Chemical characterization and two-step cure kinetics of a high performance epoxy adhesive system

Abstract

The cure kinetics of a high performance epoxy adhesive system based on TGDDM/DGEBA/DDS/DICY and toughened with carboxy terminated poly(acrylonitrile-co-butadiene) rubber with aluminum filler was investigated using differential scanning calorimetry. Three different sets of experiments were performed to follow the cure kinetics of the adhesive in a multi-step cure cycle. Three-dimensional plots of data entered into a surface-fitting software allowed for the interpolation of the degree and rate of cure as functions of heating rate and temperature, time and temperature, or time and initial degree of cure. Isothermal cure was modeled successfully using the kinetic model of Kamal. The gel point of the adhesive was measured using dynamic shear rheometry under isothermal conditions. Methods were developed to combine ramp and soak segments so that both the conversion (α) and rate of cure (dα/dt) can be followed through a two-step cure cycle of the type used to cure composite prepreg and adhesive in an industrial setting.