The Role of Carbon Black in the Action of Light on Rubber

Abstract

Abstract The action of light on rubber was studied with reference to the rate of elongation at constant stress of films, 100–150µ thick, obtained from solutions of rubber to which channel carbon black had been added by milling. The measurements were made in an apparatus, described earlier, which was equipped with a rolling carriage. When structure formation takes place as a result of irradiation of a film, the film stretches more slowly than one that has not been irradiated. If the structure is destroyed, the film elongates at a faster rate. The films were irradiated by a mercury quartz lamp P RK-2 in air at a distance of 5 cm., both when relaxed (preliminary irradiation) and while stretched (continuous irradiation). The light filters listed in Table 1 were used. The average temperature in the experiments was 25° ± 0.1° C. A film was stretched in the quartz apparatus, which was equipped with a jacket, about 1 cm. thick, in which distilled water or a solution of the light-filtering substance was circulated. The water and also the solutions were provided with an ultra-thermostat. The temperature of the water leaving the jacket was measured by a thermometer, and was kept constant within ± 0.1° C.