Surface modification of polypropylene films deposited by dielectric barrier discharge in air

A novel technique has been developed to modify the surfaces of the polypropylene (PP) films by dielectric barrier discharge (DBD) in air at a substrate temperature of 20°C, The microstructures and properties of the PP films were characterized with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. The results show that the DBD surface modification significantly affects the surface morphology, chemical stoichiometries and properties of the PP films. For instance, The DBD surface modification roughens its surfaces and introduces some polar functional groups. As the discharge time increases, its water contact angle decreases, saturating at 53° after a discharge time longer than 8 seconds. Moreover, aging effect of the modified PP films, 12 days storage in air, has little impact on its water contact angle, which is found to be still much lower than that of the control sample.