Thermal effects on the bulk luminous transmittance and track recording characteristics of dyed cellulose nitrate detectors

Simple heat treatment of polymers produces various typical morphological and chemical changes which consequently alter their physical and track registration properties. Bulk colour fading and alpha-track annealing effects have been studied in Kodak Pathe red-dyed cellulose nitrate film LR-115, type II and another Kodak product CA80-15, lightly rose-tinted cellulose nitrate, as a result of thermal annealing (room temperature to 1550C for times of 30 min to 16 h). The degree of colour fading has been measured in terms of percentage transmission of ordinary white light as sensed by a cadmium sulphide photoconductive cell, imitating the response of the human eye. It is found that at a given temperature, the transmittance rises first and acquires near-saturation after a certain annealing time. In the measurements reported here, it is seen that near-saturation transmittance is approximately proportional to the square root of the product of annealing time and temperature. The possibility of using these colour fading and transmittance measurements as an index of latent track fading is described. (orig.)