The characterization of PP/NBR blends by positron annihilation lifetime spectroscopy (PALS): The effect of composition and dynamic vulcanization

The influence of dynamic vulcanization and blend composition on the free volume properties of polypropylene (PP)/nitrile butadiene rubber (NBR) blends has been studied by using a novel technique based on positron annihilation lifetime spectroscopy (PALS). The non-vulcanized blends presented an increase of average free volume size holes and relative fractional free volume, which is an indication of incompatibility between the blend components. The dynamic vulcanization decreased the PALS parameters because of the presence of the crosslinking both inside the rubber phase and, probably, at the interface. In spite of the significant difference in PALS parameters observed as a function of the vulcanization, the mechanical properties were similar for non-vulcanized and vulcanized blends of similar composition.