REACTION OF POLYMER RADICALS FORMED BY THE DECOMPOSITION OF AZOPOLYMER WITH CARBON-BLACK SURFACE .4. STUDIES ON GRAFTING ONTO CARBON-BLACK HAVING FEW FUNCTIONAL-GROUPS

The grafting of polymers based on the radical reactivity of polycondensed aromatic rings of the carbon black surface was investigated. When carbon black was heated with azopolymers in toluene above 70-degrees-C, the corresponding polymers were grafted onto carbon black. For instance, by the reaction of furnace black with an azopolyamide (M(n)BAR = 9.6 X 10(3)) at 100-degrees-C, the percentage of grafting was 39.0%. When the azopolymer was reacted with carbon black at 40-degrees-C, where the azopolymer scarcely decomposed, no grafting onto carbon black was observed. These results indicate that polymer radicals formed by the decomposition of the azopolymer was trapped by the surface of carbon black. It was found that the reactivity of azopolymers to carbon black decreased with an increase in the molecular weight of azopolymer. The percentage of grafting onto channel black,which have many quinonic carbonyl groups, was larger than that onto furnace black or acetylene black. This indicates that not only polycondensed aromatic rings but also quinonic carbonyl groups act as trapping sites of polymer radicals. In any event, the grafting onto carbon black by use of azopolymers was concluded to be effective for grafting onto carbon black having few functional groups, such as furnace blacks and acetylene blacks. The polymer-grafted carbon black produced a stable colloidal dispersion in good solvents for grafted chains.