Aging analysis of high voltage silicone rubber/silica nanocomposites under accelerated weathering conditions

Abstract

Silicone rubber (SiR) is extensively used in outdoor insulation and other applications. However, like other polymers, SiR also degrades and lessens its performance in the exposition of environmental stresses. Nanofillers improve the aging behavior of polymeric insulating materials. To investigate the effect of nanosilica on the aging behavior of SiR, we fabricated nanocomposites of SiR with 2.5 wt.% nanosilica (SNC-2.5) and 5 wt.% nanosilica (SNC-5) by mechanical mixing and ultrasonication method. The prepared samples were subjected to uniform ultraviolet (UV) radiation, heat, humidity, salt fog, and acid rain along with neat SiR in cyclic manner at 2.5 kV for 5000 h in a specially fabricated weathering chamber. Neat SiR and both nanocomposites showed gradual decrease in transparency. Random loss and recovery in hydrophobicity and increase and decrease in leakage current (LC) were recorded for all samples, in which SNC-5 showed the best hydrophobic behavior and least LC. For SNC-5, Fourier transform infrared (FTIR) results showed negligible reduction in absorption peaks at important wave-numbers and increase and intactness were observed at absorption peaks related to the hydrophobic methyl group. Scanning electron microscopy (SEM) results also concurred with FTIR, LC measurements, and hydrophobicity analysis.