Influence of filler size on impact properties for polypropylene (PP)/elastomer/filler ternary composites was investigated. Calcium carbonate (CaCO(3)) particles with a diameter in the range from 120 to 1200 nm were used as a filler and polystyrene-block-poly(ethylene-butene)-block-polystyrene triblock copolymer (SEBS) was used as an elastomer. In the PP/SEBS/CaCO(3) ternary composite, CaCO(3) particles and SEBS particles were dispersed in the PP matrix separately. In the case that SEBS elastomer volume fraction was below 0.12, the impact strength improved gradually with a decrease of CaCO(3) mean diameter from 1200 to 160 nm. In the case that SEBS volume fraction was above 0.17, the impact strength improved significantly by the incorporation of CaCO(3) particles with a mean diameter in the range from 120 to 900 nm. However, the impact strength hardly improved by the incorporation of CaCO(3) particles with a mean diameter of 1200 nm. (C) Koninklijke Brill NV, Leiden, 2011