Characterization of polymer adsorption on disordered filler surfaces by transversal 1H NMR relaxation

The transversal H-1 NMR relaxation of the bound rubber shell of carbon black loaded elastomers can be decomposed into three relaxation regimes corresponding to the loosely bound rubber, the rubber that is immobilized on the carbon black surface and a.third component of intermediate mobility. The relaxation time T-2 of the intermediate component is related to the end-to-end distance of polymer segments between adsorption sites on the carbon black surface, by converting the relaxation times to length scales on the basis of recent work on NMR relaxation of elastomeric networks. From measurements on SBR loaded with carbon black N 220, a distance of 2.3 nm was obtained in agreement with characteristic dimensions of crystallite sizes and surface roughness as determined by atomic force and scanning tunneling microscopy. The analysis was applied to novel inversion blacks which give lower tan delta/60 degrees C, and rolling resistance without affecting tan delta/0 degrees C and wet skid behavior. These blacks were found to possess a higher density of adsorption sites and a greater surface roughness as compared to standard carbon blacks. In addition to the surface characterization, the analysis of the mobile component of the compound allowed the estimation of the density of entanglement couplings between the rubber matrix and the bound rubber shelf.