SOME IMPLICATIONS OF THE RADIATION-TREATMENT OF GRAPHITE AND CARBON BLACK

Abstract

Graphite and carbon black N234 radiation damaged with γ radiation or with neutron bombardment have been studied with Raman spectroscopy. The radiation damaging results completely evident in the case of graphite with the development of the ID band, but it is less evident in the case of an already disordered material like carbon black. The radiation damage caused by γ radiation appears comparable to that caused by neutrons, at least for the radiation dose used. Moreover, in both cases there are evidences that the radiation-induced defects appear in carbon material under the form of fullerene-like sites (onion-like carbon and carbon nanotubes) as well as under the form of hexagonal diamond and hence sp3 hybridized carbon. Neutron damaged carbon black once treated with laser light at 782 nm shows a featureless Raman spectrum with a maximum at 2287 cm−1 suggesting that neutron bombardment followed by laser light annealing causes the formation of carbyne (polyyne) domains. The radiation treatment of graphite, carbon black and even amorphous precipitated silica enhances in a spectacular way their natural rubber adsorption power. This has been measured through the “bound rubber phenomenon” which is the irreversible rubber grafting reaction on filler surface. This enhancement has been attributed to the increased concentration of “defective” sites on filler surface induced by radiation treatment which improves the rubberfiller interaction. Another macroscopic consequence of this increased interaction can be manifested in SBR-based or in natural rubber based vulcanizates filled with radiation pre-treated carbon blacks. In both cases a dramatic improvement in the reinforcing effect as measured by stress-strain curve can be observed.