New aspects of transversal H-1-NMR relaxation in natural rubber vulcanizates

Structure and dynamics of unfilled and carbon black filled natural rubber vulcanizates were investigated by means of transversal H-1-NMR-relaxation. A simple theoretical model including different motions in polymer network was extended by the discussion of an anisotropy parameter of segmental motion not only for the intercrosslink chains but also for the dangling ends. It makes characterization of the filling state of the network possible to approximate. The effect of increasing correlation times tau(f) of the fast anisotropic local motion with reduction of the molecular mass of intercrosslink chains which was observed, but not cleared up in previous investigations is evidently smaller by using this modified model in accordance with the expectation of a local motion. The determined values of M(c) are in good agreement with the results of fits by using the unmodified relaxation function. C-13-NMR-spectra and stress-strain-experiments are leading in most cases to similar results, especially for M(c).