The effects of aluminium and zinc fillers on curing characteristics, mechanical, thermal, and electrical properties and swelling behavior of natural rubber (NR) were studied. Rheometer results indicated that the incorporation of aluminium and zinc fillers enhance the curing process. Higher difference torque (M H -M L ) values were observed for aluminium-filled NR composites compared to zinc. For mechanical properties, increasing zinc filler loading in NR composites resulted in increment of tensile strength, elongation at break, and tensile modulus. However, the addition of aluminium fillers in NR reduced the tensile strength and elongation at break but showed increment in tensile modulus. Aluminium-filled NR composites shows better retention in tensile strength after thermal ageing compared to that of zinc-filled NR composites. The better electrical conductivity was observed for the composites filled with aluminium filler. The investigations showed that the particle size of both fillers influences the electrical properties of NR composites. Swelling behavior indicates that swelling percentages of both fillers-filled NR composites decreased with increasing filler loading whereas zinc filler showed better filler-matrix interaction compared to aluminium filler at all filler loading. Scanning electron microscopy (SEM) on tensile fracture surface of aluminium-filled NR composites showed poorer filler dispersions and wettability than zinc-filled NR composites. Thermogravimetric analysis (TGA) results indicate that the aluminium-filled NR composites have higher thermal stability than do zinc-filled NR composites.

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