Study on the Preparation, Properties, and Mechanism of Polysilazane‐Modified Silica and Its Flame‐Retardant Silicone Rubber Composites

In this study, three kinds of surface‐modified silica were synthesized to improve their compatibility with silicone rubber and the flame‐retardant effect. The introduction of modified silica not only enhanced the mechanical properties of silicone rubber, especially the tensile strength and elongation at break, but also improved its electrical insulation properties significantly, including increased volume resistivity and breakdown strength. The tensile strength and elongation at break of SR/SBM‐1 (10.8 MPa, 431%) are 8.0% and 4.4% higher than those of SR/SB (10.0 MPa, 413%), respectively. In addition, the modified silicone rubber showed excellent flame retardancy, with an increased limiting oxygen index (LOI) of 34.7% and V‐1 rating in the UL‐94 vertical flame test of SR/SBM‐2, while the LOI of SR/SB was only 31.3%. The phosphorus‐containing polysilazane‐modified silica also provided the silicone rubber with excellent resistance to thermal and radiation aging, which ensures the stability of the physical and chemical properties during long‐term use. The phosphorus‐containing polysilazane‐modified silica significantly improved the overall performance of silicone rubber, making it more reliable and high‐performance material for high‐end applications such as aerospace, power systems and electronic devices.