Modification of polypropylene monofilament was carried out by the graft polymerization of 1-vinylimidazole (VIm) using simultaneous radiation grafting method. The effect of radiation dose, monomer concentration, and the grafting medium on the degree of grafting was evaluated. It was observed that the presence of organics as additives in the reaction medium had significant influence on the graft levels. These grafted sutures were characterized using several techniques, such as infrared spectroscopy (IR), X-ray diffraction, and differential scanning calorimetry (DSC). It was found that the grafts are confined to the amorphous region of the monofilament and the crystalline regions remain intact. The surface morphology of structures was evaluated by scanning electron microscopy. (c) 2006 Wiley Periodicals, Inc.