Influence of Viscosity Ratio on the Mechanical, Morphological, and Rheological Properties of Thermoplastic Dynamic Vulcanizates from Devulcanized Tire Rubber and Polypropylene

In this study, we examined the effect of matrix viscosity on the properties of thermoplastic dynamic vulcanizates (TDV) produced using devulcanized ground tire rubber (dGTR) and polypropylene (PP). Polypropylenes with substantially different MFI were used to demonstrate the effect of viscosity on the properties of the resulting TDV. We examined the temperature dependence of the viscosity ratio of the components during dynamic vulcanization and found that if the viscosity of PP is closer to that of the dGTR blend, more time is allowed for the crosslinked rubber particles to disperse. We examined the TDVs thoroughly, performing tensile, acoustic emission, falling weight tests, morphological, and rheological analysis. We found a clear trend between scorch viscosity ratio and the main mechanical properties: all properties improved with increasing scorch viscosity ratio. We also found a significant decrease in rubber grain size distribution in connection with the increasing matrix viscosity, leading to improved toughness.