Effects of prestrain applied to poly(ethylene terephthalate) substrate on microstructures and morphologies of porous TiO(2) film and optical scattering behaviors of light.

Abstract

A mold was designed to simulate a thin ceramic film coating on a soft, flexible substrate using a rotating deposition system. With this mold, three prestrains (2%, 4%, and 6%) were applied to a polyethylene terephthalate (PET) substrate before the deposition of a thin TiO(2) film. The contact angle of the substrate and, thus, the mean TiO(2) particle size were affected by the prestrain. The effects of the mean particle size of TiO(2) on the surface roughness and cavity area ratio of the porous film and on the scattering behavior of light were investigated. A goniophotometer and Advanced System Analysis Program were employed for the light analyses of bidirectional scatter distribution functions and their calibration. A spectrometer with an integrating sphere was applied to determine the total scatters (TSs) of transmittance and reflection. An increase in the prestrain increased the mean particle size of TiO(2) deposited on the substrate and, thus, the mean surface roughness, cavity/void depth, and cavity area ratio. PET/TiO(2) specimens with various prestrains were prepared that satisfy the Harvey-like model but without the isotropic, diffusive property in scatter. The bidirectional transmittance distribution function area and (TS)(transmittance) results are governed by the mean particle size and, thus, the cavity/void geometries and surface roughness. These values decrease with increasing PET prestrain. The bidirectional reflection distribution function area and (TS)(reflection), however, are governed by the adsorbed carbon and its absorption thickness. These values increase with increasing C(1s) peak value in x-ray photoelectron spectroscopy spectra.