PERFORMANCE OPTIMIZATION AND MOLECULAR DYNAMICS MECHANISM OF COMPOSITE INSULATING SILICONE RUBBER AFTER ELECTRIC HEATING POST-TREATMENT

Abstract

This study investigates the optimization of composite silicone rubber (SR) through a physical electrothermal post-treatment process that functions as an efficient structural annealing method. The aim is to enhance the material’s intrinsic properties without relying on formulation modifications. Experimental results show that post-treatment at 300 °C for 1 h significantly improved the material’s mechanical properties, achieving a simultaneous increase in stiffness and toughness: tensile strength and Young’s modulus (YM) rose by 45 % (to 14.9 MPa) and 56 % (to 0.75 GPa), respectively, while elongation at break improved to 391 %. Molecular dynamics (MD) simulations were employed to understand the microscopic mechanisms behind these improvements. The post-treatment process increased the crosslink density (CD) from 78 % to 92 %, leading to a densified molecular chain network, with a reduction in the free volume fraction (FVF). The simulated YM growth (+49 %) closely matched the experimental increase (+56 %), confirming that crosslink network optimization was the main contributor to performance enhancement. Thermal performance analysis revealed that the glass transition temperature (Tg) increased from –48.5 °C to –42.1 °C, alongside an improvement in thermal stability. Electrical properties also improved, with a reduction in the dielectric constant and an increase in insulation resistance by 24 % (to 310.7 MW). This study demonstrates that electrothermal post-treatment, guided by MD simulations, effectively enhances the performance of SR, offering a reliable endogenous optimization alternative to traditional additive-based modification techniques.