A microdeformation of a simple polymer blend of polypropylene (PP) and ethylene butene rubber (EBR) was investigated in this study. Injection molding-induced morphology close to the surface was analyzed by transmission electron microscope, polarizing optical microscope, and Fourier transform IR spectroscopy. Breakup and coalescence of EBR particles scarcely occurred during the injection process. The EBR particles near the surface were observed as continuous fibers and were gradually changing to the ellipsoidal shape in the depth direction. The morphology in an injection molded specimen was related to depth profiles of mechanical factors, which were microhardness and shear stress measured by a Vickers and a Knoop microindenter and "Surface and Interface Cutting Analysis System," respectively. Crystal structure of PP matrix affected to the rnicrodeformation more strongly than that of EBR phase. The large oriented EBR domains disconnected continuity of the PP matrix and acted as a weak layer in the specimens. Finally, cohesive fracture occurred in the peel test of painted PP/EBR was discussed from a microdeformation point of view. (c) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2590-2600, 2010