Abstract
The structural change of natural rubber with mastication was examined by 'H pulsed NMR. Although the conventional pulsed NMR method gives the spin-spin relaxation time (T2), the fraction (F) and the Weibull index (W), the method has subjectivity and ambiguity in the separation of components. By applying the Gaussian expansion to the spin-spin relaxation decay, the relaxation spectrum was obtained as a relationship of relaxation time and component. The decay curve was reconstructed from relaxation spectrum in good agreement with the measured decay. The main peak of the relaxation spectrum, which corresponds to entangled network chains, became broad with the decrease of molecular weight caused by mastication. Since the broadening was observed only in the longer side of relaxation time, the broadening is considered to correspond with the increase of the non-network chains and the loose entanglements. Expansion by Gaussian or other series is one of the effective measures to avoid subjectivity in pulsed NMR analysis, and also gives more information in combination with conventional parameters (T2, F, and W).
