Effects of surface modification by Ar+ irradiation on wettability of surfaces of poly(ethylene terephthalate) films

Abstract

AbstractSurfaces of poly(ethylene terephthalate); PET, films were irradiated with Ar+ at 1 keV using various ion doses (ID) from 1014 to 1017 ions/cm2 (isc) with and without an O2 environment. The wettability of the modified surfaces of PET was determined by measuring the contact angle between water droplets and the modified surfaces. The modified surfaces were also characterized by AFM (atomic force microscopy) and XPS (X‐ray photoelectron spectroscopy) for changes in the surface morphology, and the chemical composition and molecular structure, respectively. The contact angle decreased from 70° for unmodified surfaces to 45° for modified surface with ID = 1014 isc without O2 and remained relatively constant with higher ID. The contact angle, however, reached a minimum value of 8° for modified surfaces with ID = 1016 isc with O2. The improved wettability may be due to a combination of the formation of hydrophilic groups, chemical and molecular structural changes, physical structural or morphological changes, and increased roughness of the surface. The wettability of the modified surfaces also depended on the time of exposure to air. The wettability worsened with exposure time to air, but was revived by immersing the films into water. Possible mechanisms for the change of the wettability of the modified surfaces are given.