Abstract
The polymerization of vinyl monomers has been carried out in the presence of carbon using initiators such as benzoyl peroxide (BPO) and azobisisobutyronitrile (AIBN) in nitrogen or oxygen atmosphere. The results indicate that free radicals formed by the decomposition of initiators, beside the inherent unpaired electrons of carbon black, react with carbon blacks to give active sites on their surface which then capture either the free radicals or the growing polymer radicals.Using the monomers with negative e values, such as styrene and vinyl acetate, a marked retardation was observed in BPO-initiated polymerizations in the presence of furnace black.On the contrary, using the monomers with positive e values, such as methyl methacrylate and acrylonitrile, carbon black-BPO system acted initially as an inhibitor and then as an accelerator. The phenomena may be responsible for the newly formed unpaired spins having an electron acceptability. On the other hand, it was shown that furnace black-AIBN system is almost independent of the e values of monomers.
Furthermore, it was found that the reaction of BPO with furnace black in the presence of oxygen gives a newly quinonic oxygen on the surface. As the result, the polymerization reactions using BPO in oxygen were found to promote grafting of the growing polymer radicals onto the surface of furnace black, consequently giving polymer-grafted particles while hindering the formation of homopolymers.
