Modelling of UV optical ageing of optical fibre fabric coated with TiO2

Abstract

Optical fibre fabric developed by Brochier® Technologies Company is studied for water treatment field application. By TiO2 deposition on this type of textile, the interaction between photocatalyst and UV irradiation can be strongly improved. Indeed the internal irradiation promotes the absorption of light. However, the problem is the ageing of optical fibres induced by UV exposure in the presence of TiO2 coating.Two different optical fibre fabrics were compared in term of optical ageing properties. One optical fabric was coated by TiO2 only; the other fabric was protected by a silica layer before being coated by a photocatalyst. Irradiance measurements of local light emission along ageing process were carried out and were fitted with a theoretical expression of the phenomenon. Macroscopic observations were related to microscopic behaviour on the surface of the fabric. Optical Microscopy (OM) before and after UV exposure confirm the theoretical model suggesting that the ageing induce an increase of existing holes besides appearing of new holes.These measurements show an important ageing under UV irradiation of the fabrics not protected by a SiO2 layer, leading to inhomogeneous light distribution at the surface of the textile. In presence of SiO2 layer between fabrics and TiO2 layer, no ageing was observed. Moreover, as SiO2 is transparent to UV, the photocatalyst activity does not change.