’Green’ car tyre produced from two scarcely mixable materials

Dutch technologists have carried out research into a more environmentally friendly car tyre. The scarcely mixable substances silica and rubber were mixed in a ratio that produced a tyre with a low rolling resistance and therefore a lower fuel use for the vehicle to which it will be fitted.

Louis Reuvekamp from the University of Twente mixed silica and rubber under the influence of organosilane. Tyre manufacturers normally use carbon black instead of silica to strengthen the rubber of car tyres. The organosilane used by the researchers acted as a coupling agent. It binds to the surface of silica and rubber, thus linking together two substances which can scarcely be coupled otherwise.

The ideal coupling temperature was determined experimentally. A temperature of at least 130 degrees Celsius is needed for the coupling agent to react with silica. The reaction temperature must not rise above 150 degrees Celsius, as at this temperature the rubber vulcanises and becomes too hard for further processing.

The researchers discovered that zinc oxide disrupts the coupling. However, zinc oxide is an essential part of the final tyre. Therefore, zinc oxide is now added after the coupling reaction and this has been found to work well.

Silica grain size was found to influence the rolling resistance and silica split into minute particles reduced this the most.

The researchers have requested a patent for an engine mount made from silica reinforced rubber. Up until now such mounts have nearly always been made from natural rubber. A synthetic rubber with silica gives a temperature-resistant mount. Synthetic rubber mixed with natural rubber provides a temperature-resistant mount that also does not tear easily.

For further information please contact Dr Louis Reuvekamp (University of Twente, Faculty of Science and Technology) tel. +31 (0)53 4894621, e-mail: l.a.e.m.reuvekamp@ct.utwente.nl.
The doctoral thesis was defended on 14 February 2003. Dr Reuvekamp’s supervisor was Prof. J.W.M. Noordermeer.