Why is synthetic rubber used for car tyres rather natural rubber?
1 Answer
Natural rubber is used for car tyres, but except for tyre base it is supplemented by other rubbers.
Explanation:
Typically tyre tread is 50% natural rubber and 50% styrene-butadiene rubber (SBR). The tyre base is 100% natural rubber. The sidewall is about 75% natural rubber and 25% SBR, and the inner liner is 100% isobutylene/isoprene rubber (no natural rubber).
Natural rubber on its own is not durable enough to withstand the forces exerted from the pressure of the road under the load of the car, so it can only really be used on its own for the tyre base. The tread needs a much tougher material, so SBR is used 50:50 with natural rubber to give increased toughness and strength, plus durability under heavy friction. It also raises up the softening point of the rubber so that when the tread is hot (due to friction and/or hot weather) it doesn't soften too much.
Of course there are many other materials used in tyres other than rubbers, steel belting and beadwire for example, which gives ultimate strength to the tyre. Like many every day items, tyre construction is a lot more complicated than you may imagine.
