Postgrafting of N-vinyl-2-pyrrolidone onto a plasma modified polypropylene surface

Surface grafting of polymeric materials such as films and fibers improves their reactive surface properties. Poly(propylene) (PP) reactive sites, which should initiate surface postgrafting, can be formed by a nitrogen plasma treatment. It has been shown that grafting of N-vinyl-2-pyrrolidone (NVP) onto different PP plasma-modified surfaces bearing alkyl radicals or hydroperoxides is efficient but the physicochemical properties of the grafted layer are dependent on plasma and grafting conditions. Alkyl radicals are mon reactive and initiate the growth of 20 monomer units per radical onto the surface against 12 for hydroperoxide groups. When grafting is initiated with alkoxy radicals, kinetics depend on hydroperoxide decomposition rate and the obtained hydroxyl radicals react with NVP to produce a homopolymer in non negligeable proportion for a duration longer than 25 h.