| Network structures in carbon black filled, TBBS-sulfur vulcanized natural rubber (NR) and synthetic cis-1,4-polyisoprene (IR) have been studied by high-resolution solid-state C-13 NMR and equilibrium swelling experiments. Incorporation of carbon black affects the composition of the sulfurization products, while the total amount of sulfurization reactions was not altered by the black loading. The total amount of physical crosslinks linearly increases with carbon black content. The grade of the carbon black affects the amount of physical crosslinks but not that of the sulfurization products. It is assumed that physical adsorption, rather than chemical bonding, may play an important role in the polymer-filler interactions. Comparable reinforcement effects of the carbon black are observed between NR and IR systems. The efficiency of the intermolecular crosslinking reactions becomes maximum at 90% cure state (t90) in NR and IR gum formulations.;The average amount and the distribution of the spin-spin relaxation time, T... |
