The mechanism of the enzymatic grafting of high-density polyethylene (HDPE) films with acrylamide compounds was studied. The potential for using horseradish peroxidase (HRP) to graft acrylamide onto the surface of HDPE films was examined. Several analytical approaches provided evidence that the chemical composition and morphology of HDPE surfaces were changed after grafting. Results show that the surface of treated films becomes rougher than the untreated surface. Compared to unmodified HDPE, modified HDPE surface had significantly increased absorbance in the UV-visible region, and the N-H and carbonyl-stretching regions in the IR spectra. The hydrophilicity of treated and untreated HDPE films was analyzed by staining and contact angle measurements. The decreased contact angle of the HDPE film with water and increased adsorption ability of the surface to a water-soluble dye clearly indicated that enzymatic grafted acrylamide could significantly increase the hydrophilicity of the surfaces of HDPE films. Moreover, the hydrophilicity of treated film depend upon the monomer concentration, the initiator concentration and oxidizing agent concentration as well as the time of the reaction, its optimum value appears when the monomer concentration, the initiator concentration, H2O2 concentration and the reaction time were 0.15 M, 3.0 x 10(-2) M, 6.0 x 10(-3) M, and 300 min, respectively. (C) 2004 Elsevier B.V. All rights reserved.