Kinetics of radiation grafting of N-vinyl pyrrolidone (NVP) onto poly(ethylene terephthalate) (PET) fabric revealed the existence of four different processes. These are as follows: the grafting, the homopolymerization, the degradation, and the diffusion. The grafting process was followed by the increase in weight with the increase in irradiation time (t), while the homopolymerization and the degradation processes were evaluated from changes in the square root of the specific viscosity of the irradiated monomer solution (root eta(sp)) with the increase in t. All processes were carried out at different NVP concentrations, different irradiation temperatures (T), and a dose rate 1.31 Gy s(-1). All processes followed first-order kinetics except the degradation process that followed a 0.6-order. The rate (R) and rate constant (k) of grafting and diffusion processes were found to increase with the increase in T, while the homopolymerization and degradation processes showed negative temperature dependence. The sum of R of the four processes was proportional to the initial NVP concentration, while k of the four processes was independent of T and has a value of 0.674 min(-1). The respective apparent activation energies of 24.0, 6.24, 6.84, and 2.5 kJ mol(-1) were calculated for the four processes. The NVP molecules participated in each process and their energies were evaluated. (c) 2006 Wiley Periodicals, Inc.