Evaluate the effect of graphene and milled glass fibre on the thermal, flame and dielectric properties of silicone elastomer filled with aluminium hydroxide

In this work, the thermal stability, thermal conductivity, dielectric frequency response, smoke factor (SF), fire performance index (FPI), and fire growth index (FGI) of silicone elastomer composites were studied and compared. TGA/DTG results indicated that the addition of graphene nanoplatelets (GNP)/milled E-glass fibres (MGF) improved the thermal stability of silicone composites by increasing the Tmax2, T20% and T30%, whereas thermal conductivity was improved by 93%–115% compared to RTV1 and 12%–24% compared to RTV2. Based on the GNP/MGF loadings, a low relative permittivity and low dielectric loss were observed. Furthermore, GNP/MGF filled silicone composites exhibited high FPI and low FGI, and microstructure analysis revealed a compact bottom char layer with no crevices on the surface. The most promising silicone composites were RTV4 and RTV5, which had higher thermal stability, improved thermal conductivity, excellent FPI and FGI values, and excellent dielectric properties, making them more suitable for electrical outdoor insulation exposed to fires.