The melt-free radical grafting of glycidyl methacrylate (GMA) onto powered isotactic poly(1-butene) (iPB-1) using styrene (St) as a comonomer in a Haake mixer was studied. The effects of temperature, initial GMA, and peroxide concentration, as well as the addition of St comonomer, on the final grafting degree, grafting efficiency, and the melt flow rate of grafted polymer were studied. It was shown that the addition of St as a comonomer could significantly enhance the grafting degree of GMA on iPB-1 and reduce the extent of degradation of iPB-1 to some degree. It has been found that the grafting degree of dual-monomer melt-grafted iPB-1 was about twice that of single-monomer-grafted iPB-1 for the same monomer and peroxide concentrations. The grafting of GMA onto iPB-1 remarkably accelerated the crystal form II -> I transformation of iPB-1. POLYM. ENG. SCI., 51: 1669-1674, 2011. (C) 2011 Society of Plastics Engineers