Controlling the Morphology in Epoxy/Thermoplastic Systems

Thermosets are frequently toughened by a high-T-g thermoplastic (TP). Blend morphologies obtained by curing induced phase separation with scales of a few hundreds of nanometers are relevant for high-performance applications, but no quantitative description for obtaining these morphologies exists yet. We propose such a quantitative approach for predicting and controlling the final morphology. The key is the degree of curing and the corresponding T-g of the blend and both phases when phase separation takes place. It is controlled by the Flory interaction parameter chi of the constituents and their respective T-g's. We show that if phase separation takes place too early during curing, the T-g is too low and the morphologies grow to reach sizes of a few micrometers or more. Our study of different systems allows us to propose the relevant range of Flory interaction parameter chi and temperature window T-T-g for which the sizes of interest may be obtained. Our work opens the way for devising thermoplastics-thermosets couples with the appropriate affinity and T-g's in order to make blends with tailored morphologies.

Automated summary

The present study proposes a quantitative approach for predicting and controlling the final morphology of thermosets toughened by high-T-g thermoplastics. By controlling the degree of curing and the T-g of the blend and both phases during phase separation, the desired sizes can be obtained. This research is of great importance for designing blends with tailored morphologies.