After one atmospheric pressure plasma treatment of poly(ethylene terephthalate) (PET) film, acrylic acid (AAc) in aqueous solution was successfully graft-copolymerized onto PET films. The effects of reaction time, AAc monomer concentration and reaction temperature on grafting behavior of AAc were systematically studied. Possible reaction kinetics of plasma-induced graft copolymerization, starting from initial hydroperoxide decomposition, were proposed. Through the Arrhenius analysis about graft copolymerization kinetics of AAc monomers on PET surface, it was revealed that the activation energies of decomposition, propagation and termination were 98.4, 63.5, and 17.5 kJ/mol, respectively. The temperature around 80 degrees C was favorable not only for the formation of oxide radicals through the thermal decomposition of hydroperoxide on PET surface but also for the extension of graft copolymer chain through direct polymer grafting. Poly(acrylic acid) (PAAc) grains grafted onto PET surfaces possessed relatively uniform size and both PAAc grain size and surface roughness increased with increasing the grafting degree of AAc. The increase of grain size with increasing grafting degree results from the possibility of forming long chain graft copolymers and their shielding of reactive sites. (C) 2008 Wiley Periodicals, Inc.