HYDROPHILIC SURFACE MODIFICATION OF POLYPROPYLENE FILMS BY CCL4 PLASMA

The CCl4 plasma treatment of polypropylene films was investigated from the viewpoint of hydrophilic surface modification using a contact-angle meter, ATR FTIR spectroscopy, and angular XPS. Hydrophilicity and chemical composition of the CCl4-plasma-treated polypropylene films were discussed. The CCl4 plasma treatment was effective in hydrophilic modification. The advancing contact angle of water for polypropylene films was decreased from 99-degrees to 81-7-degrees by the CCl4 plasma treatment, and the surface energy increased from 27.2 to 38.9-67.7 mJ/m2 when the discharge current varied from 50 to 150 mA. The CCl4 plasma initiated chlorination, oxidation, and aluminum sputtering reactions. The chlorination of polypropylene films was favorable in a mild CCl4 plasma operated at a discharge current of 50 mA. The oxidation and aluminum sputtering reactions were predominant over the chlorination in strong CCl4 plasmas operated at discharge currents of more than 75 mA. The chlorination initiated by the mild CCl4 plasma was restricted near the film surface within 36 angstrom deep. The regions modified with the strong CCl4 Plasma reached inner layers of 36-49 angstrom deep. Hydrophilicity caused by the CCl4 plasma treatment may be due not only to chlorine functionalities but also to oxygen and aluminum functionalities.