NMR imaging of the competitive vulcanization of natural rubber and polybutadiene blends

NMR imaging was used to study the spatial heterogeneity of the molecular mobility of the competitive vulcanization of natural rubber and high-cia polybutadiene blends. The NMR images showed the presence of domains of widely different molecular mobilities. This heterogeneous mobility reflects differences in the crosslink density internal to each component of the blend. The differences in the internal crosslink density probably arise from differences in diffusion and solubility of the curatives. Additionally, overall, the poor dispersion of sulfur and accelerator due to inadequate mixing also contributes to the heterogeneity.