Photooxidation of Poly(vinyl butyral) Films by UV/Ozone Irradiation

Poly(vinyl butyral), PVB was photooxidized by UV/ozone irradiation and the effect of UV energy on the surface properties of the UV-irradiated PVB film were investigated by the measurement of reflectance, surface roughness, contact angles, elemental composition, and zeta potential. With increasing UV energy, reflectance decreased in the visible and ultraviolet regions particularly at the wavelength of 400nm. The irradiation produced nano-scale surface roughness including the maximum peak-to-valley roughness increased from 274nm for the unirradiated PVB to 370nm at the UV energy of 5.3J/cm². The improved hydrophilicity was due to the higher O1s/C1s resulting from the introduction of polar groups such as C=O bonds. The surface energy of the PVB film increased from 35.3mJ/m² to 39.3mJ/m² at the irradiation of 15.9J/cm². While the zeta potentials decreased proportionally with increasing UV energy, the cationic dyeability of the PVB increased accordingly resulting from the improved affinity of the irradiated PVB surfaces containing the photochemically introduced anionic and dipolar dyeing sites.