Long term water adsorption ratio improvement of polypropylene fabric by plasma pre-treatment and graft polymerization

Although the hydrophilicity of polypropylene (PP) fabric surface can be improved by plasma treatment, it would obviously decay with the storage time. In this study, the graft polymerization of acrylamide (AAm) onto the surface of PP fabric was carried out by plasma pre-treatment and subsequently induced by UV-induce surface graft polymerization to improve the long term water adsorption ratio of the substrate. During the process, peroxides formed by the plasma treatment are the major factor responsible for initiating the graft polymerization. The amount of peroxide can be determined with good accuracy by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method. Results indicated that the amounts of peroxides obviously increased with the plasma treated time and treat power, and the maximum concentration of peroxide can reach about 6.0 x 10(-7) mol/cm(2). However, the degree of grafting was not monotonous with increasing plasma treated power. The optimum processing condition was to apply 30 W power with 10 min of treatment to achieve the maximum surface grafting efficiency. Although the surface of PP fabric can be changed from hydrophobic to hydrophilic after plasma treatment, it would obviously age after 4 d of storage. By contrast, the UV-induce surface graft polymerization of PP can keep their hydrophilic property during the storage time after 7 d, due to the covalently grafted with hydrophilic monomer.