Gelation kinetics in elastomer/thermoset polymer blends

The chemical gelation of polymer blends involving a thermoset component has been investigated utilizing multiple waveform dynamic rheology, complement ed by differential scanning calorimetry and small angle x-ray scattering me asurements. Three epoxy/rubber mixtures, with different degrees of pre-reac ted material and catalyst, were used. The curing temperatures were determin ed with simple temperature ramps, whereas the characteristic gel times were quantified using the well-known self-similarity of the gel structure, whic h yielded a very low gel exponent (0.05), indicative of the high molecular weights and additives used in the samples; this exponent was unchanged with temperature, suggesting the same gelation mechanism. These times decreased with increasing temperature. Gelation was not affecting the phase-separate d morphology. The presence of pre-reacted material and catalyst were found to reduce the gel times (for different temperature steps). Finally, the she ar history of the samples did not affet the curing temperatures and kinetic s. These results can serve as a useful guide for appropriately blending the rmosetting and thermoplastic compounds in order to obtain structural materi als for different applications.