Evidences of rubber grafting on activated carbon surfaces containing fullerene-like structures

It is shown that graphite is converted into an high disordered carbon black by prolonged ball milling. The kinetics of this transformation has been followed by powder x-ray diffraction, measurements of the crystallinity and of the surface area. Ball milling is able to introduce an high concentration of defective sites in the pristine graphite including the fullerene-like structures. By mixing with natural rubber both the pristine and the ball-milled graphite, it is shown by bound rubber measurements that the amount of rubber grafted (chemically linked) on the pristine graphite surface is negligible but reaches a very high level in the ball-milled graphite. Similarly, ball-milling of N660 carbon black causes a deep activation of its surface activity which can be measured by significant increase in the bound rubber level and in the amount of grafted rubber in comparison to the pristine N660 sample. The bound rubber measurement has been performed also on a natural rubber masterbatch with extracted fullerene carbon black (EFCB). Also in this case extremely high levels of rubber grafting have been achieved in comparison to graphite. It is discussed and demonstrated that the fullerene-like nanostructures in carbon blacks play a key role in the formation of bound rubber phenomenon and in grafting natural rubber on carbon black surface.