One polypropylene (PP) was mixed with two ethylene butene copolymers (EBM). EBM1 had 12.5 mol % of butene and was immiscible with the PP. EBM2 had 51.6 mol % of butene and was miscible with the PP. The dispersed PP in EBM1 showed fractionalized crystallization behavior with a crystallization temperature at around 45 degrees C and a much slower isothermal crystallization rate comparing to the neat PP. The PP did not exhibit fractionalized crystallization behavior in EBM2. EBM1 did not decrease both the crystallization and melting temperatures of the continuous PP. However, EBM2 could decrease both the two temperatures. It was found that EBM2 could largely suppress the epitaxial lamellar branching of the PP. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012