The graft copolymerization of glycidylmethacrylate (GMA) onto modified nylon-6 fibers containing polydiallyldimethylammonium chloride (PDADMAC) groups in the presence of (Cu (2+)-K2S2O8) as a redox initiating system was carried out, with very high extent and almost without homopolymer formation. The mechanism of the graft polymerization induced by this system was suggested. The rate of grafting was determined by varying the monomer, K2S2O8, and cupric ion concentrations as well as the amount of PDADMAC. The kinetic investigation revealed that the rate of graft- ing (Rp) of GMA onto modified nylon-6 fibers is roportional to [GMA](1.83), [CuSO(4)center dot 5H(2)O](0.46), [PDADMAC](0.4), and [K2S2O8](1.43). The overall activation energy was 134.7 kj/mol. The fine structure and thermal properties of the grafted nylon-6 fibers were investigated. (c) 2005 Wiley Periodicals, Inc.