Polypropylene (PP)/elastomer/fine filler particle ternary composite was prepared using polystyrene-block-poly(ethylene-butene)-block-polystyrene triblock copolymer (SEBS) or carboxylated SEBS (C-SEBS) as elastomer and calcium carbonate (CaCO3) having mean size about 160 nm as filler. First, SEBS (or C-SEBS) and CaCO3 particles were mixed to form master batch. Second, the prepared master batch and PP matrix were kneaded. In the PP/SEBS/CaCO3 ternary composite, CaCO3 particles and SEBS particles were dispersed in the PP matrix separately. In the PP/C-SEBS/CaCO3 ternary composite, CaCO3 particles were encapsulated in C-SEBS and formed a core-shell structure at lower CaCO3 concentration; however, some CaCO3 particles were dispersed in PP matrix at higher CaCO3 concentration. In the PP/SEBS/CaCO3 composite, the impact strength increased with the amount of incorporated CaCO3 particles. Whereas, in the PP/C-SEBS/CaCO3 composite, the impact strength increased with the amount of CaCO3 particles dispersed in PP matrix. The master-batch method was found to be useful for improving the dispersibility of CaCO3 particles than the commonly used single-batch method. (C) Koninklijke Brill NV, Leiden, 2009