Determination of crosslink densities of carbon black filled natural rubber sulfur vulcanizates by 13C NMR MAS spectroscopy and 1H NMR transversal relaxation

Two NMR spectroscopic methods were applied to carbon black filled NR vulcanizates to determine the chemical crosslink density. Both methods give corresponding results. Addition of carbon black leads to a decrease of crosslink density with increasing filler content. The influence is more pronounced at higher sulfur content.