Determination Of The Origin Of The Narrow Esr Signal In Carbon-Black Filled Polymers

A comparison of the ESR and ENDOR signals generated during the melt blending of carbon blacks and polymers with the signals generated upon electrochemical reduction of the carbon blacks has been made. Both an oxidized and an unoxidized carbon black were used. For the oxidized black, the magnetic resonance spectra revealed a localized site on the surface which interacted with the hydrogen nuclei of the polymer. However, for the unoxidized black, a conduction ESR signal was observed which also interacted with the polymer matrix. In both cases it was concluded that the narrow ESR signal of the composite was equivalent to the electrochemically reduced signal of the carbon black. This in turn demonstrates that the narrow ESR signals observed in composites arise from electron acceptance by the carbon blacks. Finally, the possible mechanisms for this reaction are discussed.