Mechanical properties and microstructure of hybrid vulcanized natural rubber filled with carbon black and nano-CaCO 3 from Achatina achatina Shells

Nano-CaCO 3 (NCC) obtained from Achatina achatina shells were used as single filler and as partial replacement of carbon black (CB) to produce vulcanized natural rubber (NR) filled at 5, 10, 15, 20, 25 and 30 pphr. The SEM micrographs showed that the dispersion of the fillers in the hybrid composites up to 15wt% replacement of CB was very good. Higher strengths were obtained up to 25 pphr for composites that contained 95wt%CB/5wt%NCC and 90wt%CB/10wt%NCC, while the composites that contained 85wt%CB/15wt%NCC showed higher strength up to 20 pphr compared to the CB filled samples. The NR filled with hybrid CB/NCC up to 15wt% replacement of CB offered comparative hardness and abrasion resistance; while 95wt%CB/5wt% NCC filled sample showed lower compression set over CB reinforced samples up to 30 pphr and comparative tensile strength, hardness, elastic modulus and abrasion resistance. As single filler, the synthesized nanoparticles imparted significant improvement in the mechanical properties of vulcanized NR; however, the properties were inferior to the CB reinforced sample due to poor dispersion of the NCC in vulcanized NR. The thermal and oxidative stability of the hybrid composites up to 15wt% replacement of CB were better than those of the CB filled samples.