On the coarsening of co-continuous morphologies in polymer blends: effect of interfacial tension, viscosity and physical cross-links

The coarsening of co-continuous morphologies in polymer blends with anneali ng is studied, demonstrating the effect of interfacial tension, viscosity a nd also physical cross-links in blends with thermoplastic elastomers. Go-co ntinuous morphologies of 50/50 wt% stay co-continuous with annealing but sh ow a linear increase in phase size with time. The 30/70 wt% blends break up into droplet/matrix morphologies and shows an increase in phase size in th e first stage of the coarsening process. A relation has been proposed, usin g only the interfacial tension and viscosities of both components, to predi ct the growth rate of coarsening. The relation shows good agreement with th e rates found experimentally. The coarsening process in blends with thermop lastic elastomers is severely slowed down or even stopped when physical cro ss-links are present in the thermoplastic elastomers. The driving force for coarsening is too small to overcome the stabilizing force due to physical crosslinks. (C) 2000 Elsevier Science Ltd. All rights reserved.