NR/XSBR nanocomposites with carbon black and carbon nanotube prepared by latex compounding

Abstract

Two series of natural rubber/carboxylated styrene butadiene rubber (NR/XSBR) (80/20) nanocomposites containing different loadings of carbon black (CB) (3-9 phr) and carbon nanotube (CNT) (0.1-0.4 phr) have been prepared by a latex stage compounding method. Before mixing with NR/XSBR blended latex, CB and CNT were dispersed and stabilized in water by ball milling with the aid of surfactant. The obtained compounded latex was cast into sheet on a glass mold and thereafter cured in an oven at 80°C for 3 h. The tensile properties (tensile strength, modulus at 300% strain, elongation at break), dynamic mechanical properties (loss tangent, storage modulus) and thermal stabilities (degradation temperatures, % char) of the vulcanizates were evaluated. The results showed that the addition of either CB or CNT enhanced the tensile strength, modulus at 300% strain, storage modulus and thermal stability, but reduced the elongation at break of the NR/XSBR blend in a dose dependent manner, except that the tensile strength peaked at an optimum filler level, declining at higher filler loadings. The CNT-filled nanocomposites provided a comparable tensile strength with that of the CB-filled nanocomposites but at about 25-fold lower loading. This reinforcing effect is attributed to the greater aspect ratio and specific surface area of CNT.