The present article focuses on the effect of two types of inorganic fillers (SiO2 and CaCO3) on the mechanical properties of PP/SEBS blend. The nominal particle diameters of SiO2 and CaCO3 are 7 nm and 1 mu m, respectively. The studied blend ratios were PP/SEBS/SiO2 (CaCO3) = 75/22/3 and 73/21/6 vol %. The morphology of polymer blends was observed and the distribution of the SEBS, SiO2, and CaCO3 particles were analyzed by transmission electron microscopy (TEM). Tensile tests were conducted at nominal strain rates from 3 x 10 (1) to 10(2) s(-1). The apparent elastic modulus has the local strain-rate dependency caused by SiO2 nanoparticles around SEBS particles in the blend of PP/SEBS/SiO2. The yield stress has weak dependency of morphology. The absorbed strain energy has strong dependency of the location of SiO2 nanoparticle or CaCO3 fillers and SEBS particle in the morphology. It is considered that such morphology, in which inorganic nanoparticle are located around SEBS particles, can prevent the brittle fracture while the increased local strain rate can enhance the apparent elastic modulus of the blend at the high strain rate. On the basis of the results of this study, the location and size of inorganic nanoparticles are the most important parameters to increase the elastic modulus without decreasing the material ductility of the blend at both low and high strain rates. (c) Wiley Periodocals, Inc.