NMR of Reinforced Elastomers: Part II. The Influence of Carbon Black Dispersion

Abstract 1. NMR measurements can provide a fast and efficient monitor of the incorporation and dispersion of carbon black in a reinforced rubber compound. Tests can be carried out at all stages of processing, including masterbatch stock. 2. The technique provides a determination of the fraction of polymer which is bonded to the surface of the carbon black particles. Within a specific formulation, there is reasonably good correlation between the percentage of bonded polymer, determined by NMR, and the degree of dispersion of carbon black determined optically. 3. Bonded polymer formation is sensitive to carbon black type and to the nature of the host elastomer. In comparison of different formulations, there is no correlation between the fraction of bonded polymer and the dispersion of the black. However, carbon black-rubber attachments are fundamental to the phenomenon of reinforcement and, in this respect, NMR bonded-polymer measurements can provide a valuable probe for the investigation of reinforcement. ...