Block Copolymer Toughening of Epoxy—Effect of Vitrification Temperature on Morphology and Fracture Toughness

ABSTRACT The influence of the vitrification temperature on the phase separation of block copolymer modified epoxy systems and the resulting fracture mechanical properties is investigated. It is found that the temperature‐driven demixing process causes dominantly phase separations in the nanoscale when polymerized at 23°C, whereas microscale phase separations occur during polymerization at 80°C. The nanoscale phase separations result in higher values of fracture toughness K 1c and fracture energy G 1c . With increasing block copolymer concentration, fracture toughness and fracture energy further increase.