Hydrophilic surface modification of polypropylene films by CCl 4 plasma

The CCl 4 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 CCl 4 plasma treatment was effective in hydrophilic modification. The advancing contact angle of water for polypropylene films was decreased from 99° to 81‐7° by the CCl 4 plasma treatment, and the surface energy increased from 27.2 to 38.9‐67.7 mJ/m 2 when the discharge current varied from 50 to 150 mA. The CCl 4 plasma initiated chlorination, oxidation, and aluminum sputtering reactions. The chlorination of polypropylene films was favorable in a mild CCl 4 plasma operated at discharge current of 50 mA. The oxidation and aluminum sputtering reactions were predominant over the chlorination in strong CCl 4 plasmas operated at discharge currents of more than 75 mA. The chlorination initiated by the mild CCl 4 plasma was restricted near the film surface within 36 Å deep. The regions modified with the strong CCl 4 plasma reached inner layers of 36‐49 Å deep. Hydrophilicity caused by the CCl 4 plasma treatment may be due not only to chlorine functionalities but also to oxygen and aluminum functionalities. © 1993 John Wiley & Sons, Inc.