Influence of the processing on the completion of curing in epoxy-based composites

Differential scanning calorimetry analysis was used to investigate interrelationships between several thermal parameters and the processing conditions of particle-fitled thermosetting resins. On the same piece, obtained by injection molding, epoxy-based composites exhibited sensible differences within a set of measurements of the glass-transition temperature, the width of the transition, the difference in the heat capacity, and the conversion degree. Statistical analysis showed a strong intercorrelation between these thermal parameters, but it could not provide any explanation for the disparities. The dispersion of the measured properties could, in a second step, be directly related to a sample's position with respect to the injection point in the mold. Moreover, even the postcuring stage could not erase this topological effect. As a result, a phenomenological model is proposed that fairly describes the experimental trends. This simple polynomial approach can subsequently be used either to determine the thermal parameters of any point of a molded piece or to shed some light on phenomena responsible for the large variations of the measured quantities. (c) 2005 Wiley Periodicals, Inc.