Immiscible and incompatible binary blends of commercial polypropylene (PP) /polyethylene (PE) display poor mechanical properties. The addition of compatibilizer to reinforce and enhance an adhesion at the interfaces between PE-PP mixtures has been conducted. The compatibilizer chosen was in the group of Ziegler-Natta's PE-PP block copolymer with diisocyanate linkage. The effects of adding the compatibilizers, were assessed by morphology studies, thermal analysis, and mechanical testing. DSC curves of crystallization and FTIR provided evidences to support the formation of PP/PE block copolymer. Significant improvements in the mechanical properties of 50/50 PE/PP blends containing compatibilizer have been noted. (c) 2007 Wiley Periodicals, Inc.