Abstract: Carbon nanotubes(CNTs)/styrene-butadiene rubber(SBR) composite powders prepared by spray drying method was mechanically mixed with a two-roller open mixer. Influences of the mechanical mixing on the mechanical properties of the composites were investigated and the theoretical mechanism of such influences was analyzed. The results show that mechanical mixing effectively enhance the mechanical properties of CNTs/SBR composites particularly for those with high content of CNTs which are much better than those filled with the same content of carbon black. CNTs could be further dispersed homogeneously in the matrix through mechanical mixing. On the other hand, because of large shear force during the mixing process and the formed free functional groups, the interactions between CNTs and the rubber matrix such as physical absorption, hydrogen bonding and chemical bonding were improved that increased the combined rubber contents of the composites. Correspondingly CNTs could be more efficient in strengthening the SBR. Therefore the tensile and tear strengths of the composites were improved after the mechanical mixing. The strengthening effect of CNTs in SBR probably accorded with the “strong and weak bonding” mechanism.

Key words: Carbon nanotube, Styrene-butadiene rubber, Mechanical property, Spray drying method, Mechanical mixing