Grafting Reaction of Reactive Groups Introduced onto Carbon Black Surface with Functional Polymers Having Termin al Hydroxyl or Amino Groups

Abstract

The grafting of polymers onto carbon black by the reaction of reactive groups introduced onto the surface with functional polymers having terminal hydroxyl or amino groups was investigated. Surface carboxyl and phenolic hydroxyl groups present on carbon black were found to be able to covert into chloroformyl, azidocarbonyl, isocyanato, blocked isocyanato, 2, 4-dichlorotriazinyl ether, epoxide, phthalic anhydride, 1-imidazolylcarbonyl, pentachlorophenyl ester, and p-nitrophenyl ester moieties. Although isocyanato groups introduced onto carbon black were readily deactivated even if it was stored in vacuo, the content of other reactive functional groups scarcely decreased when these carbon blacks were stored in vacuo. It was found that by the heating of carbon black having these functional groups with functional polymers, such as polypropylene glycol (PPG), polyethylene glycol, and poly( iminoethylene), the corresponding polymers were grafted onto the surface: the percentage of grafting was determined to be 15-60%. On the contrary, when untreated carbon black was heated with these polymers, the grafting of polymers onto the surface was hardly observed. Furthermore, these polymers grafted onto carbon black surface were readily removed from the surface by the hydrolysis with alkali. Based on the above results, it was concluded that these founctional polymers are grafted onto carbon black surface with chemical bonds, such as ester, amide, and urethane bonds. The percentage of polymer grafting onto carbon bl ack increased with increasing molecular weight of functional polymers, but the number of grafted polymer chain decreased. It was found that the relationship between the number of grafted chain (G) and molecular weight (M ) of founctional polymers is given by the following equation (K and a are constan ts): 0, 1=K x/17/Polymer-grafted carbon black gave a stable co lloidal dispersion in a good solvent for grafted polymer, but immediately precipitated in a non-solvent.1023