Effect of TiO2 on the mechanical and adhesion properties of RTV silicone elastomer coatings

Abstract

Silicone elastomer coatings (SEC) have been of interest for marine application due to their good surface properties. However, they suffer from low mechanical properties and poor adhesion to substrate. In this work, the effect of the TiO 2 content on the mechanical properties of a SEC, including tensile strength and modulus, hardness and abrasion resistance were studied. The effect of TiO 2 on the adhesion strength of SEC top layer to a tie layer was also investigated and the results were correlated to the mechanical properties of SEC. The results revealed that the inclusion of TiO 2 in the SEC affects various properties of the coatings. The extent of the effect, however, depends on the TiO 2 loading. Tensile tests, initially, showed a relatively rapid increase of the modulus with TiO 2 content. This was then followed by a decrease in modulus as TiO 2 was further increased. The pull-off test results showed an increase in the adhesion strength with increasing TiO 2 up to 10 wt.%, beyond which, the trend was reversed. The former is assumed to be due to an increase in the cohesive strength of the coating while the later is attributed to a pigment accumulation and difficulty in its dispersion.