Ground Tyre Rubber/Waste Polypropylene Blends – Effect of Composition on Mechanical Properties

Abstract

Ground tyre rubber (GTR) was blended with waste polypropylene (WPP) in nine different compositions to prepare GTR/WPP blends. The blends were prepared in a Haake Rheocord PolyLab system at a temperature of 180 °C and a rotor speed of 30 r/min for 8 min. The processing characteristics of the blends showed an increase in steady-state mixing torque with an increase in GTR content, suggesting an increased difficulty in processability at GTR loadings above 30 wt.%. Morphological observations of the blends showed two-phase systems. The GTR was dispersed in a continuous WPP matrix in blends containing up to 60 wt.% GTR, and the size of the dispersed GTR agglomerants increased with GTR content. At 70 wt.%, the GTR dispersed phase changed to a continuous phase. Tensile strength, modulus, and tear resistance decreased with GTR content, while the elongation at break and the impact failure energy increased. All these properties remained relatively unchanged at low GTR contents, suggesting that a critical GTR level is required to obtain rubber-like properties in a simple rubber–thermoplastic blend.