Effect of phase structure on the adhesion properties of the dimethoxysilyl-terminated polypropylene oxide/epoxy resin system

Abstract

In order to investigate the effect of phase structure on the adhesion properties of the dimethoxysilyl-terminated polypropylene oxide (DMSi-PPO)/diglycidyl ether of bisphenol A (DGEBA) system, various cured resins with different phase structures obtained by varying the formulations and curing temperatures were prepared. DGEBA that formed micro-order spherical domains reinforced the DMSi-PPO matrix in the cured system. Under ambient cure conditions, the adhesion properties of the cured system decreased with the addition of more than 50 phr DGEBA, because of the large domain size distribution and coagulation in the phase structure. However, it showed good adhesion properties when cured at 80°C. SEM observations showed that the phase structure became a unimodal micro-order domain size with increasing curing temperature. The reason for the dependence of the phase structure on the curing temperature is considered to be the different degree of solubility of DGEBA in DMSi-PPO. The fine phase structure in the 80°C-cured system resulted in a higher bulk cohesive energy and higher deformability, not only because of the increase in the surface area of the DGEBA domain but also due to the fine particle size distribution. The different bulk behaviors of the cured systems were reflected in the lap shear strength and T-peel strength.