In this research, the rheological properties of electron beam irradiated polypropylene homo polymer (PP) containing Polybutene (PB) resin and Trimethylol Propane Trimethacrylate multifunctional monomer is studied. The effect of PB resin in inducing long chain branches on the PP backbone are evaluated by various viscoelastic parameters. The zero shear viscosity (eta(0)) of samples containing 5% PB resin considerably decreased to 5500 Pa s, from eta(0) = 11,500 Pa s, which indicates the plasticizing effect of PB resin on the ease of movement of PP macromolecules. It is found that the presence of PB resin enhanced the branching by facilitating the movement of PP macromolecules in solid state and increasing the recombination efficiency of PP macro radicals. The mobilizing effect of PB resin also reduced chain scission and degradation of PP resin which is traced by shifting the cross over frequency. The PB free radicals formed during the irradiation process can bound to PP free radicals and suppress the degradation process. The evaluation of zero shear viscosity ratios and crossover point ratios of irradiated samples to un-irradiated ones confirmed that using small amount of PB resin increase branching efficiency, which is the evidence of mobilizing effect of PB resin. (C) Wiley Periodicals, Inc. J Appl Polym Sci 123: 2036-2041, 2012