Silicone rubbers filled with TiO2: Characterization and photocatalytic activity

Compounding of silicone rubbers with TiO2 was carried out in a two-roll mill from a mixture of TiO2 and poly(dimethylsiloxane) (PDMS) with several other additives. The silicone matrix was crosslinked by a platinum-catalyzed hydrosilylation reaction. Characterization of the rubbers was performed by thermogravimetric and dynamic mechanical analyses, swelling measurements in toluene and in a salicylic acid/water solution, UV–vis spectroscopy and field emission scanning electron microscopy. The photocatalytic activity of the rubbers was evaluated with respect to the photodegradation of salicylic acid in aqueous solution under UV radiation, by measuring total organic carbon. The thermal stability of the PDMS matrix was enhanced by the addition of 10 phr (parts per hundred parts of rubber, by weight) of TiO2, but a further increase in the quantity of TiO2 favored thermal degradation of the matrix. The stiffening effect promoted by the incorporation of TiO2 into the matrix was more pronounced at higher TiO2 amount. The increase in the quantity of TiO2 also promoted a decrease in the crosslinking density of the matrix, favoring the swelling of the rubbers. The rubber with 78 phr of TiO2 degraded 56% of the salicylic acid from an aqueous solution.