Influence of organic modified silica coatings on the tribological properties of elastomeric compounds

The frictional behaviour of elastomers has attracted a lot of attention and interest in order to better comprehend its effect on the skidding features of tires and the performance of different rubber components, such as gloves, contact rubber seals and diaphragms, and elements of weapons. In the present work, for the first time, silica coatings were deposited on the surface of different elastomeric compounds (i.e. butadiene rubber (BR), styrene-butadiene rubber (SBR) and silica loaded butadiene rubber (BRs)) by dip-coating technique, with the aim to modify their surface properties, leading to a decrement of the friction coefficient. A green sol-gel methodology was exploited, avoiding the use of toxic chemical substances. The influence of the silica coating on the surface properties of the elastomeric compounds was deeply investigated by means of scanning electron microscopy (SEM), static contact angle measurements and tribological tests. The obtained coatings were characterised by an average thickness of around 1-2 mu m, flexibility, due to the presence of cracks, developed during the drying process, a very good adhesion to the elastomeric substrates in the case of thinner coatings (1 dip-samples). Moreover, they provided an enhanced hydrophobic behaviour, lower surface free energies and lower friction coefficient values (friction coefficient decrease up to 30%).