Both 80/20 and 60/40 polypropylene/poly(ethylene-co-octene) (PP/POE) blend samples were collected from four positions along a single-screw extruder, which can induce chaotic and shear mixing, respectively. Results indicated that a wide range of impact strengths was obtained as the formation of series of phase morphologies. For the 80/20 blends, the impact strength increased gradually along the extruder with shear mixing due to gradual decrease of both diameter and size distribution coefficient of droplets. Whereas the impact strengths reached the highest value at about 2/3 length of the whole screw with chaotic mixing as the formation of lamellas, then decreased as their breakup. For the 60/40 blends, the impact strength reached the highest value as the formation of the thick fibrils with shear mixing; whereas the impact strength became higher at about 2/3 length of the whole screw as the formation of thin fibrils and the highest (69 times of that of pure PP) at the end of the screw due to the formation of cocontinuous structure with chaotic mixing. Observing the fractured surface of the tested sample with cocontinuous structure revealed that a distinct deformation of the PP matrix was induced by the shear yielding during impact testing. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers