Effect of functionality and content of epoxidized soybean oil on the physical properties of a modified diglycidyl ether of bisphenol A resin system

Partially epoxidized soybean oil (pESO) and fully epoxidized soybean oil (fESO) were used respectively to modify a diglycidyl ether of bisphenol A (DGEBA) resin system in this study. The pESO was prepared by epoxidizing soybean oil and the fESO was purchased as it was commercially available. DGEBA/ESO ratio of the epoxy resin system was changed from 100/0 to 70/30 and triethylenetetramine was used as a curing agent. Impact strength of the bio-epoxy resin system with fESO increased with ESO content, but the system with pESO decreased with ESO content. The bio-epoxy resin system with pESO showed higher tensile strength and elongation at break than the system with fESO at ESO 30 wt%. Tensile modulus and thermal degradation temperature decreased with ESO content and glass transition temperature was highest at 20 wt% ESO regardless of epoxide functionality of ESO. The performance of the DGEBA/ESO bio-epoxy resin system could be tailored by changing ESO content and functionality.