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

Abstract

Differential scanning calorimetry analysis was used to investigate interrelationships between several thermal parameters and the processing conditions of particle-filled 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.

Physical properties of epoxy resin/titanium dioxide nanocomposites

“…The completion of this process overlapped with the endothermic peak that followed at higher temperatures. This peak was present only in the first heating scan and depicts physical aging in the epoxy network [35–38]. This process involves the relaxation of residual stresses (enthalpy relaxation) because of the immobilized polymer chains in a thermodynamic nonequilibrium state [37, 39, 40].…”

Influences of degree of curing and presence of inorganic fillers on the ultimate electrical properties of epoxy-based composites: experiment and simulation

“…For the C2 composite, a sampling of materials was carried out with various conversion degrees close to the optimal cure state [17]. The resulting set of samples however presented slightly different curing times and temperatures, which led, with the help of the Di Bendetto equation [18] to six conversion degrees ranging from 0.95 to 0.995 (figure 1).…”