Radical graft polymerization of polypropylene (PP) with acrylic amide derivatives was studied in a melt extrusion process. Fourier transform spectroscopy (FTIR) results and nitrogen analysis confirmed that acrylamide (AAM), methacrylamide (MAM), N-tert-butyl-acrylamide (NTAAM) and N-tert-butylmethacrylamide (NTMAM) were successfully grafted onto PP, and the grafted products were employed as precursors of biocidal N-halamine polymers. Monomer structures affected grafting efficiency and polymer chain scission reactions on the polymer. Addition of styrene (St) as a co-monomer in the grafting process was studied. Addition of St significantly prevented polymer chain scission, though, could increase or decrease grafting content of vinyl-amide monomers. The reactivity ratios of the multi-monomer systems during melt-grafting process were evaluated through Fineman-Ross method. The halogenated products exhibited powerful antimicrobial properties against Escherichia coli and Staphylococcus aureus. In addition, the possible hydrolysis mechanism of acyclic N-halamine polymers during several recharging cycles were proposed based on experimental data. (C) 2008 Elsevier Ltd. All rights reserved.