Development of silicone rubber-based nanocomposites: nanoparticle selection and performance analysis

Silicone rubber (SR) is high-voltage insulator, but suffers from poor mechanical properties. Nanoparticle addition is a promising way to combat this problem. Herein, SiO2, Al2O3, MgO, SiC and thermally modified SiC nanoparticles were used to improve electrical resistivity, thermal stability and mechanical properties of SR. Surprisingly, electrical resistivity of SR was enhanced by one-order-of-magnitude by incorporation of small amount of nanoparticles, which induced nano-scale traps to capture charge carriers and restrict SR molecules conformation. Tensile strength and modulus of SR increased by SiO2, Al2O3, MgO and SiC incorporation, while decreased elongation at break, as a consequence of agglomeration as detected by microscopic observations. Nano fillers restricted the motion of polymer chains, so storage modules and hardness were increased. Addition of 2 phr SiC resulted in less polarization current comparably. Correspondingly, dielectric breakdown strength of the assigned sample was increased. SiC thermally modified interface is more conductive than the other parts of the matrix reduced charge accumulation and provide more conductive ways for increased charge carriers mobility, dissipate more charges and then increased dielectric breakdown strength. Dynamic-mechanical-thermal analyses demonstrated that storage modulus of SR nanocomposites was comparatively higher than neat SR, owing to rigidity contributed from SiO2 and SiC nanoparticles. Evidently, glass transition temperature shifted to a higher temperature (-109 degrees C) compared to the neat SR (-127 degrees C). Thermogravimetric analysis witnessed superiority of thermal stability of nanocomposites compared to SR, featured by 35 degrees C rise in degradation temperature. The presence of nanoparticles in the polymer matrix acts as a barrier and prevents the release of gaseous products from burning and the entry of oxygen into the system lead to increase thermal stability.