Surface modification of polypropylene by radiation grafting of hydrophilic monomers: physicochemical properties

The surface of polypropylene was modified by the post-irradiation grafting of acrylic acid (AAc), N,N-dimethylacrylamide (DMA) and mixtures of AAc (DMA) and a quaternary ammonium salt (QAS). The polypropylene sheets were activated by electron beam radiation before the grafting reaction. The degree of grafting was determined by weighing and the surface hydrophilicity was measured by measuring the water contact angles. The presence of oxygen and nitrogen was demonstrated by XPS. The surface charge and the isoelectric point were determined by the streaming potential method. The grafting of DMA, like that of AAc, depended on monomer availability, but the monomer did not permeate into the polypropylene bulk. For the same surface hydrophilicity, depending on the nature of the monomer or comonomer grafted, it is possible to modulate the physicochemical characteristics which determine the phenomena governing adhesion, and probably to adapt them to a given application.