Silicone rubber composites incorporating graphitic carbon nitride and modified by vinyl tri-methoxysilane

Increasing attention has been paid to the design of high-performance polymer composites applied in high voltage insulation field, and typical composites are comprised of either micro-scaled or nano-scaled inorganic fillers. In this work, we prepared bulk graphitic carbon nitride (g-C3N4) from melamine via thermal condensation, and silicone rubber (SR)/C3N4 composites were prepared via direct mechanical blending followed by in-situ modification by vinyl tri-methoxysilane (VTMS). The formation of the bulk g-C3N4 from melamine was confirmed by XRD, FTIR and XPS. Increasing the g-C3N4 content improved the mechanical properties of the composites. The role of VTMS in the modification of bulk g-C3N4 was revealed to serve as the molecular bridge between the SR matrix and g-C3N4 filler, which strengthened their interfacial interaction. Therefore, the incorporation of VTMS reduced the defects in the as-prepared composites, which resulted in the enhancement of both breakdown strength and mechanical properties. Moreover, the SR/C3N4-VTMS composites exhibited a higher dielectric constant and a lower dielectric loss at high frequency range compared to the SR/C3N4 composites.