Permanent hydrophilic modification of polypropylene and poly(vinylalcohol) films by vacuum ultraviolet radiation

Abstract

Polypropylene (PP) and Poly(vinyl alcohol) (PVA) both synthetics polymers but one of them biodegrad-able, were surface modified by vacuum ultraviolet (VUV) irradiation. After VUV irradiation in an inertnitrogen atmosphere, the films were exposed to oxygen gas. The treated films were characterized bywater contact angle measurements (WCA), optical profilometry, FTIR-ATR, XPS, UPS and NEXAFS tech-niques. PP and PVA VUV-treated films reached superhydrophilic conditions (WCAs <10◦) in about 30 minof irradiation under our experimental conditions. It was observed that when the WCAs reached about35?40◦the hydrophilicity was permanent in both polymers. These results contrasted with typical plasmatreatments were a rapid hydrophobic recovery with aging time is usually observed. UPS and XPS datashowed the presence of new functionalities on the PP and PVA surfaces that were assigned to COO, C O,CO and C C functional groups. Finally, grafting of styrene (ST) as a typical monomer was tested on PPfilms. It was confirmed that only in the VUV irradiated region an efficient grafting of ST or polymerized STwas found. Outside the irradiated regions no ST grafted was observed. Our results showed the potentialuse of VUV treatment for surface modification and processing of polymers which lack chromophores inthe UV region