There isn't any natural rubber in a tyre's construction. But there are about 200 raw materials from man-made rubbers, reinforcing fillers, rayon, nylon, all sorts of additives and aramid fibres.
Aramids are heat-resistant synthetic fibres with tradenames like Kevlar and Nomex.
This mix is susceptible to damage from ozone and ultra-violet light so manufacturers add carbon black to absorb the UV radiation and convert it to heat which is dissipated harmlessly.
Carbon black is also very hard-wearing.