Aging effects on vulcanized natural rubber studied by high resolution solid state C-13-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 sulf ur system are studied by solid state C-13-NMR spectroscopy. Cis-trans isome rization and different sulfide structures are detected and identified throu gh the chemical shift values of the extra NMR lines, which are observed in the various vulcanizates. It is shown that the kinetics of crosslink format ion map be followed by this technique. A destruction of the polysulfidic cr osslinks is clearly related to the aging process in the conventional system of cured unfilled or filled vulcanizates, whereas no significant modificat ion is observed in the peroxide and the EV cured ones. (C) 2000 Elsevier Sc ience Ltd. All lights reserved.