Synergistic enhancement of flame retardancy, insulation, and mechanical properties of epoxy resin composite via a triazine-rich phosphonitrile microcapsule core-shell filler design

The widespread application of epoxy resin (EP) in potting materials for power equipment is limited by its inherent brittleness and potential fire hazard. With the rapid advancement of power equipment toward higher voltage levels and greater capacities, this issue has become increasingly critical. Consequently, the development of EP insulating materials with enhanced flame retardancy and improved toughness is urgently needed. However, improving flame retardancy often leads to a compromise in mechanical performance. In this work, a novel microencapsulated compound, Si(HT), a phosphonitrile compound based on a triazine-rich framework, was introduced to enhance the flame retardant, smoke suppression, mechanical, and insulation properties of EP. The experimental results demonstrated that the incorporation of only 2% of the microcapsule core-shell structured Si(HT) significantly enhanced the limiting oxygen index (LOI) to 32% and enabled the material to achieve a UL-94 V-0 rating. Additionally, the AC breakdown strength increased by 58%–137.3 kV/mm, and the tensile strength improved by 14%–47 MPa, while maintaining excellent thermal stability, a low dielectric constant, and minimal dielectric loss. The synergistic effects of phosphorus, nitrogen, and silicon elements contributed to the significant improvement in the overall performance of EP. This study presents a viable strategy for broadening the application of epoxy resin in encapsulation materials for electrical equipment.