Plasma induced graft polymerization of acrylic acid onto polypropylene (PP) monofilament was carried to introduce carboxyl functionality on its surface. The monofilament was treated with oxygen plasma to create hydroperoxide groups and subsequent graft polymerization was initiated on this exposed monofilament. It was observed that in the absence of an added inhibitor, the grafting did not proceed because of the extensive homopolymerization which left behind hardly any monomer for the grafting reaction. The addition of ferrous sulfate to the grafting medium led to the homopolymer free grafting reaction. The addition of organics, such as methanol, butanone, and acetone led to complete inhibition of the homopolymerization at 60% content. However, the addition of butanone led to much lower degree of grafting than methanol and acetone. The contact angle of the monofilament showed drastic reduction by plasma treatment and by the subsequent grafting of acrylic acid. The grafting in ferrous sulfate medium showed higher contact angles as compared to the grafting in organic medium. The surface morphology was significantly influenced by the nature of the additive in the grafting medium. (C) 2007 Wiley Periodicals, Inc.