Thermal properties and fracture toughness of bisphenol-based DGEBA/DGEBS epoxy blend system

In this study, the bisphenol-based DGEBA/DGEBS blend systems were studied in cure kinetics, thermal stabilities, and fracture toughness of the casting specimen. The content of DGEBA/DGEBS was varied in 100:0, 90:10, 80:20, 70:30, and 60:40 wt%. The cure activation energies (E_a) of the blend systems were determined by Ozawa's equation. The thermal stabilities, including initial decomposed temperature (IDT), temperatures of maximum rate of degradation (T_max), and integral procedural decomposition temperature (IPDT) of the cured specimen were investigated by thermogravimetric analysis (TGA). For the mechanical interfacial properties of the specimens, the critical stress intensity factor (K_IC) test was performed and their fractured surfaces were examined by using a scanning electron microscope (SEM). As a result, E_a, IPDT, and K_IC show maximum values in the 20 wt% DGEBS content compared with the neat DGEBA resins. This was probably due to the fact that the elevated networks were formed by the introduction of sulfonyl groups of the DGEBS resin.