Effect of silica nanoparticles modified with different concentrations of stearic acid on microstructure, mechanical & electrical properties of RTV-2 silicone rubber nanocomposite

One of the main challenges in preparing ceramic-reinforced polymer nanocomposites is the agglomeration of nanoparticles. This problem has been solved by surface modification of nanoparticles. In this study, silica nanoparticles were modified with low-cost and environmentally-friendly stearic acid instead of high-cost silanes or hazardous fluorinated hydrocarbons. RTV 2 silicone rubber/SiO2 nanocomposite films containing 1wt% and 3wt% silica modified with stearic acid:silica ratios of 2:1 and 1:1 were prepared, and the effects of different concentrations of stearic acid and silica on microstructure, hydrophobicity, mechanical and electrical properties were investigated. The microstructure of the samples was studied by field emission scanning electron microscopy. Spray and contact angle tests were also done to study the hydrophobicity. Increased hydrophobicity was observed with the incorporation of modified silica into RTV-2. Results of mechanical properties tests revealed that increased stearic acid concentration caused a deterioration in mechanical properties. Among all the composite and pure samples, the sample containing 3wt% silica modified with a lower amount of stearic acid exhibited the highest hardness, elongation at break, and tensile modulus. Results of electrical tests indicated that all composite samples had lower dielectric constant and dielectric loss factor and higher surface resistance compared to the pure sample.