Effect of Interfacial Strengthening in Blends of Reclaimed Rubber and Polypropylene

Thermoplastic vulcanizates (TPVs) were prepared from polypropylene (PP) and reclaimed ground tire rubber crumbs. Three types of interfacial strengthening agents degraded PP, hydrosilylated PP, and hydrosilylated PP grafted onto styrene-butadiene rubber were prepared in melt via a stepwise series of reactions and employed to generate various degrees of interfacial adhesion in the aforementioned blends. The incorporation of the interfacial agents resulted in improvements in the mechanical properties of these TPVs, and the rubber particle size remained constant. The PP chain length and the functional groups present in the interfacial agents affected the magnitude of the improvement in the mechanical properties. The interfacial agents were primarily present on the surface of the rubber particles in the blends, as shown by energy-dispersive X-ray spectra. These interfacial agents in the PP/rubber crumb blends led to a unique preyield kink in their stress-strain curves, a plateau, or a sharp turning point in the region of approximately 3% elongation and approximately 4-MPa stress. These kinks were interpreted similarly to the cold flow of semicrystalline polymers in tension. The addition of the interfacial modifiers decreased the shear viscosity and increased the entrance pressure drop in flow through capillary dies, and this was attributed to changes in the elongational viscosity of the blends. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 1051-1059, 2010