Quantitative Measurement of Surface Oxidation of Polypropylene by O Atoms: Increase and Subsequent Decrease in Hydrophilicity Induced by O-Atom Treatment

Abstract

To examine the surface modification of polypropylene (PP) by O atoms, PP surfaces are treated using a vacuum ultraviolet (VUV) photodissociation reactive species supply method. The O-atom treatment initially reduces the water contact angle (WCA) on the PP surface; however, prolonged treatment leads to an increase in the WCA. This increase is likely due to the evaporation of low-molecular-weight oxidized materials generated by PP chain scission. The relationship between O-atom density and the observed reduction and subsequent increase in WCA is analyzed in detail. The results are compared with findings from previous studies on PP plasma treatment to elucidate the specific role of O atoms in plasma-based surface treatments.