PHYSICO-CHEMICAL STUDIES ON SOME POLYMERIC MATERIALS FOR POSSIBLE USE AS RADIATION DOSIMETERS

Abstract

The aim of the present thesis is the development of new dyed plastic films and the investigation of their possible usc as dosimeters for electron beam. gamma and/or ultraviolet radiation. First films were prepared by casting polymeric solution poly(vinyl butyral) ( PVB) incorporating pH-indicating dye, namely, thymol blue (TB) in the presence of Cl-containing substance (chloral hydrate) . These films have the advantage of clear visual change in colour at low doses (2-4 kGy) indicating their suitability for eventual application in food irradiation processing and wastewater treatment. These films were developed using the phenomenon of HCl generation from the Cl-containing substance under irradiation. The produced HCl in turn changes the colour of the indicator contained in the polymer (cf Chapters III. I). Another film made of poly(vinyl alcohol) incorporating rose bengal with and without chloral hydrate was evaluated and found as useful radiation dosimeter in the dose ranges .5-20 kGy for film containing chloral hydrate and 5-150 kGy for film without chloral hydrate. These flexible plastic film dosimeters are bleached when exposed toy-ray photons (cf Chapter lll.2) . The commercially available Riso B3 film dosimetrs was evaluated as a dosimeter for high-dose gamma radiation dosimetry using fluorometry technique. The useful dose range is 5- 150 kGy (cf Chapter JIL3). Based on a new approach of reacting ionic dyes with grafted polymeric films. new dosimeter films have been developed for high-dose gamma radiation applications in the range of absorbed dose from 50 to 400 kGy (cj: Chapter III.4). The dosimetric parameters, e.g. dose response, effect of relative humidity and temperature during irradiation on response as well as pre- and post-irradiation stability of all above mentioned films are discussed. Finally, TB/PVB film, which has been evaluated as a gamma radiation dosimeter in Chapter III. I, has been successfully used for measuring integrated UV- irradiance. This film was found to respond faithfully to UV-A, UV-B and UV-C

radiation showing maximum sensitivity at 200 um wavelength (cf Chapter 111.5).