Phase morphology modulation of silicone-modified epoxy resins and effects on thermal, mechanical and ablative properties

In this work, the modified epoxy resins with phase sizes of silicone varying from a homogeneous structure to 9.35 μm were obtained by regulating curing. The effect of silicone phase size on the mechanical, thermal and ablative properties of epoxy resins was also investigated. The increase in the degree of pre-curing slowed down the exothermic effect of the curing process and reduced the number of precipitated silicone phases leading to a large-sized phase structure. Nevertheless, the increased grafting rate induces the formation of a homogeneous structure of the silicone in the epoxy resin. Nano-scale and homogeneous phases of silicone contribute to the formation of a dense antioxidant layer, which imparts excellent thermal stability and ablative resistance to the epoxy resin. The ablation rate of epoxy resins with homogeneous phase reached 0.0671 g/s and 0.014 mm/s, which is even lower than that of conventional ablative resins. Meanwhile, the excellent mechanical properties are expected to replace expensive thermal protection materials as the main component of the new generation of thermal protection systems.