Aging effects on vulcanized natural rubber studied by high resolution solid state 13C-NMR

The vulcanization chemistry, network formation and thermal oxidative aging effects of unfilled and carbon-black filled natural rubber vulcanized with organic peroxide, efficient vulcanization (EV) system and conventional sulfur system are studied by solid state 13C-NMR spectroscopy. Cis–trans isomerization and different sulfide structures are detected and identified through the chemical shift values of the extra NMR lines, which are observed in the various vulcanizates. It is shown that the kinetics of crosslink formation may be followed by this technique. A destruction of the polysulfidic crosslinks is clearly related to the aging process in the conventional system of cured unfilled or filled vulcanizates, whereas no significant modification is observed in the peroxide and the EV cured ones.