Enhanced UV-Aging Resistance of Silicone Rubber Through Surface Modification of Montmorillonite with Polydopamine and Vinyltrimethoxysilane

Prolonged ultraviolet (UV) exposure degrades the mechanical, hydrophobic, and dielectric performance of silicone rubber (SIR) used in outdoor high-voltage insulation. Here, montmorillonite (MMT) was sequentially treated with polydopamine (PDA) and vinyltrimethoxysilane (VTMS) and incorporated into SIR at 0.5–5 phr (parts per hundred rubber). Spectroscopic and thermal analyses indicated changes in the MMT surface chemistry after treatment, and the composites were evaluated before and after 500 and 1000 h of accelerated UV aging. Among the 2 phr formulations selected for detailed comparison, SIR/2 VTMS-PDA@MMT exhibited favorable aging-property retention: after 1000 h, its tensile-strength retention was 103.2% and its elongation at break was 158%, compared with 57.7% tensile-strength retention for reference SIR. Its breakdown-strength retention was 94.6%, compared with 83.5% for SIR, and its static water contact-angle retention was 95.1%, compared with 77.8% for SIR, with comparatively small aging-induced changes in hardness and fracture morphology. The comparative results show that the MMT surface treatment and filler formulation influence the retention of mechanical, dielectric, and surface properties during accelerated UV exposure, providing guidance for the design of UV-resistant SIR composites.