Thymol-blue dyed poly(vinyl butyral) films for monitoring ultraviolet radiation

Dyed poly(vinyl butyral) (PVB) films prepared by a simple technique of casting alcoholic solution of PVB incorporating thymol blue (TB) indicator and chloral hydrate [CCl3CH(OH)(2), 2,2,2-trichloroethane-1,1-diol] on a horizontal glass plate are useful for ultraviolet radiation monitoring. These plastic films undergo colour change from yellow to red upon exposure to UV irradiation. The radiation-induced change in colour was analysed spectrophotometrically at the maximum of the visible absorption band peaking at 551 nm. These films have a pronounced response to the main UV radiation spectral regions [UVA (400-320 nm), UVB (320-280 nm) and WC (280-180 nm)] showing a maximum sensitivity at 200 nm. The measurement uncertainty of estimating ultraviolet radiation energy incident per unit area on the films is found to be 6.6% at a confidence limit of 95% (2 sigma). The study of the effect of radiance exposure, irradiation wavelength, chloral hydrate concentration and the post-irradiation stability in different storage conditions has been carried out to characterise the use of these films for actinometric monitoring ultraviolet radiation. (C) 2000 Elsevier Science B.V. All rights reserved.