Effects of Filler Loading on Properties of Polypropylene–Natural Rubber–Recycle Rubber Powder (PP–NR–RRP) Composites

Carbon black, silica and calcium carbonate were used as fillers in polypropylene–natural rubber–recycle rubber powder (PP–NR–RRP) composites. The effects of filler loading on processability, tensile properties, swelling behavior and morphology of PP–NR–RRP composites at a fixed weight ratio of 70/15/15 were studied. The blends were melt mixed using a Brabender Plasticorder torque rheometer at 190°C and 50 rpm. Filler contents were steadily increased from 0 to 30 (wt.%). The results indicated that the tensile strength and Young’s modulus increase with increasing carbon black and silica content in PP–NR–RRP composites whereas calcium carbonate exhibit opposite trend except Young’s modulus. Carbon black filled PP–NR–RRP composites exhibit lowest resistance toward swelling in ASTM oil No.3 than calcium carbonate and silica filled PP–NR–RRP composites. In terms of processability, incorporation of silica in PP–NR–RRP composites give more processing difficulties than carbon black and calcium carbonate filled PP–NR–RRP composites.