Solid‐state 13 C‐NMR investigations of crosslinked structure modifications in elastomers during heating treatment

The chemical modifications occurring during the thermal degradation of sulfur‐cured natural rubber were investigated with 13 C‐NMR. Samples of vulcanized rubbers were heat‐aged at 70°C under an air (oxidative) environment for 3, 7, and 21 days. Changes were analyzed by the measurement of the variations of the concentrations of different C–S x –C crosslinked structures during the thermooxidative process through the intensity of the related NMR lines in the 10–70‐ppm range. © 2002 Wiley Periodicals, Inc. J Appl Polm Sci 87:3–8, 2003