The synthesis of a secondary branched epoxy‐modified silicone resin and its application at low temperature

Abstract To enhance the fracture toughness of epoxy resin at low temperature, a secondary branched epoxy‐terminated silicone resin (ESR‐6) was synthesized and incorporated into bisphenol A epoxy resin at different contents. The structure of ESR‐6 was characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance ( 1 H NMR), and the fracture surface of the composites was observed by scanning electron microscope (SEM) and atomic force microscopy. At room temperature and − 70°C, the maximum values of elongation at break were 15.78% and 12.55% with 10 wt% ESR. Compared with those of neat epoxy resin, the values of elongation at break of the composite were increased by 50.86% and 36.12%. The results of dynamic mechanical analysis also showed that the toughness of the modified resin had been improved. The SEM images of the fracture surfaces suggested that the fracture mode of the modified resin changed from brittle one to plastic one because of the addition of ESR‐6, which further confirmed the toughening effect of ESR‐6. These research results may provide a new strategy for enhancing the low‐temperature toughness of epoxy resins.