Mechanical and rheological properties of partial replacement of carbon black by treated ultrafine calcium carbonate in natural rubber compounds

The present research aimed to develop natural rubber hybrid composites reinforced with treated ultrafine calcium carbonate/carbon black (CC/CB). The influence of CC/CB with various filler ratios (50/0, 40/10, 30/20, 20/30, 10/40 and 0/50) on mechanical properties and cure characteristics of the composites was investigated. Also filler reinforcing efficiency was compared aiming to achieve the best ratio for CB partial substitution as compared to composites with CC and CB incorporated separately. The CC30/CB20 composites reached around 17.56 +/- 0.3 MPa similar strength at break response compared to CC0/CB50 (16.83 +/- 0.6 MPa). Elongation at break increased 48% in relation to CC0/CB50. Hardness maintained similar values compared to high concentration of CB composites. The increase of crosslink density is attributed to a strong interaction between CC and CB and showed a synergism between filler and polymeric matrix in hybrid composites. Scanning electron microscopy studies also reveal a good filler dispersion between filler particles and matrix. The results shown that the new material can be an alternative filler for partial substitution of CB conserving mechanical properties.