The aim of this work is to study the influence of electron beam irradiation on the structure of polypropylene (PP)/polybutene-1 (PB-1) blend in the branching process. The blend with 10 wt% of PB-1 and 0.5 wt% trimethylolpropane trimethacrylate monomer is prepared and irradiated at different doses. The rheological properties of the melts in shear and extensional mode were evaluated, and their thermal behavior, crystalline structure, and morphology are studied by differential scanning calorimetry, wide-angle X-ray diffraction, and scanning electron microscopy. The presence of long chain branched structure is approved by higher zero-shear viscosity (eta(0)), longer relaxation time and pronounced strain-hardening behavior in the within the range of dose tested. By increasing the irradiation dose and enhancing chain scission in the backbone and long chain branches, the decline in melting temperature, duplication of melting peak, and the decrease in zero-shear viscosity were observed. The morphological study of the blends before and after irradiation revealed no considerable change in PB-1 droplet size and their distribution in the PP matrix. The emulsion theoretical models could predict well the rheological behavior of all samples and no significant change was observed on the interfacial interaction of PP and PB-1. (C) 2013 Society of Plastics Engineers