Abstract: Bisphenol A epoxy resin was modified by epoxy-terminated silicone. The impact strength, tensile strength, elongation at break, and glass transition temperature of the composites were investigated. The morphology of fracture surfaces was observed using SEM. The effects of modification methods and silicone content on material performance were discussed. After direct mechanical blending with epoxy-terminated silicone, the thermal resistance of epoxy resin was unchanged and the mechanical property declines clearly. When epoxy-terminated silicone was introduced via co-curing at 5 phr, the glass transition temperature of the system reached 177.35 ℃，which was higher than that of unmodified EP with 2.67 ℃. In addition to improved thermal resistance, the tensile strength almost remains unchanged and elongation at break increased from 7.6 % to 16.7 %, the impact strength increased from 20.23 KJ/m2 to 27.19 kJ/m2. A significant toughening was evidenced by the improvement of toughness and was supported by the SEM micrographs of the stretched section of cured epoxy resin.

Key words: toughening, epoxy-terminated silicone, epoxy resins, modification