Radiation grafting of acrylic acid (AA)/N-vinyl pyrrolidone (NVP) binary mixture onto poly(ethylene terephthalate) (PET) knittings was investigated by pre-irradiation technique. The influence of the grafting conditions, such as monomer composition, reaction temperature, and the effect of storage time with temperature after irradiation on the degree of grafting was determined. ATR-FTIR spectroscopy analysis of the grafted knittings confirmed the existence of amide group of NVP in the knittings. The concentration of peroxides and effect of storage time on peroxide concentration were also determined by 2,2-Diphenyl-1-picrylhydrazyl at different temperatures. There was an increase in surface roughness of grafted PET in comparison to virgin PET as determined by atomic force microscopy and scanning electron microscopy. The grafted knittings were subsequently immobilized with collagen Type I which was further apt for the study of growth and morphology of human mesenchymal stem cell (hMSC). The immobilization of collagen on PET knittings has provided an excellent surface for the growth of hMSCs. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 116-126, 2010