Rheology of epoxy-thermoplastic blends
Epoxy–thermosets hold value in many industrial applications, owing to their favorable characteristics including excellent adhesion, ease of processing, and thermal and chemical stability. Despite these benefits, the high cross-linking density of epoxy–thermosets also results in a brittleness that limits utility in many high-performance structures that are subject to high impact, such as aerospace and automotive applications. The inclusion of thermoplastics within the epoxy can improve toughness and impact resistance. Rheological analysis of epoxy–thermoplastic blends serves as a critical analytical technique for evaluating the viscoelastic properties during the pre-cure formulating stage and during the cure. Chemorheology is useful to characterize the distinct viscoelastic changes that occur during the cure of epoxy–thermoplastics, which involve phase separation, epoxy gelation, and vitrification. Through rheological modeling, the behavior during can be further evaluated to predict flow behavior and mechanisms of phase separation. Importantly, rheology meets the analytical demands in industrial applications, where details concerning preprocessing conditions, quality control, and cure cycle design are crucial.