Effects of Ph12SQ on the thermal stability and mechanical properties of high temperature vulcanized (HTV) silicone rubber

Ph₁₂SQ (C₆H₅SiO_1.5)₁₂ was blended into a polydimethylsiloxane (PDMS) based HTV silicone rubber as a reinforcing filler at loadings of (0, 2.5, 5, 10, 15, 20% by weight). The thermal stabilities and mechanical properties of these HTV silicone rubber composites were studied by thermal gravimetric analysis (TGA) and tensile testing, respectively. Dispersions of Ph₁₂SQ were characterized by scanning electron microscopy (SEM). The obtained results show the presence of SQ-rich regions that affect the thermal stabilities and mechanical properties of HTV silicone rubber. TGA shows that T_d1% is delayed from approximately 215 °C for DD₀ to 350 °C (DD₂₀) (about 130°C) and the T_d5% mass loss exhibits a similar trend. The thermo-oxidative stability also increases with Ph₁₂SQ weight fraction. Also, the tensile strength and elongation at break of these HTV silicone rubbers increase from 8.8 to 11 MPa and 655 to 950 % with incremental loading of Ph₁₂SQ to 5 wt% (DD₅). Moreover, the addition of Ph₁₂SQ increases its relative permittivity from 3.2 to 14.2 and the dissipation factor at 1 MHz increases from 0.01 to 0.05. Finally, the values of T_d5% at different heating rates were applied for comparison of the lifetime of DD₀ and DD₅ samples according to the D&R model. The results show that DD₅ offers a longer lifetime than DD₀ at different temperatures.