Ageing impact on the surface condition of silicone rubber micro nanocomposites adopting AFM studies

Silicone rubber micro nanocomposite specimens were aged in acidic (acid rain and HNO3) and saline (NaCl) solutions at 90˚C for 24 h and subsequently placed in the open air at room temperature to monitor its recovery characteristics. The specimens aged in acidic and saline solutions with high conductivity have shown better performance than the samples aged in acidic and saline solutions with normal conductivity. Lesser reduction in hydrophobicity and surface roughness after ageing and marginally faster recovery of hydrophobicity and surface roughness were observed for the silicone rubber specimens aged in NaCl solution followed by HNO3 and acid rain solutions. The micro nanocomposites have reflected the least water intake and lesser surface degradation along with better hydrophobicity compared to pure silicone rubber specimens. Surface morphological changes in aged silicone rubber specimens were analysed in detail at various decomposition levels, by employing wavelet transform to surface profile signal obtained through Atomic Force Microscopy (AFM). The fractal dimension and lacunarity parameters evaluated for the surface profile data of aged silicone rubber composites were found to increase marginally, indicating marginal increment in the complexity and the fractal surface density.