Solid State Carbon-13 NMR Studies of Vulcanized Elastomers. III, Accelerated Sulfur Vulcanization of Natural Rubber

In summary, the solid state C-13 NMR technique has proven to be a significant method for the detection of crosslinks and other structural modifications in accelerated sulfur-vulcanized NR systems. When the amount of accelerator is high in proportion to the amount of sulfur used, the network structure appears to be simpler with less crosslinking, less main chain structural modification, and fewer cyclic sulfide structures as observed in the C-13 NMR spectra. Polysulfidic crosslinks have been detected in addition to polysulfides terminated by accelerator residues. Cis-to-trans chain isomerization is also evident in these vulcanizates.