Investigation of the Aging Processes in Rubber. I. The Effect of Irradiation with Ultra-violet Light or the Surface Tension of Rubber Solutions

1. Irradiation of rubber solutions in the presence of air with ultra-violet light brings about a pronounced lowering of their surface tensions at the boundary of solution and water. This lowering is connected with the formation of oxidation products of rubber, which are surface-active. 2. The kinetics of the changes in the surface tension are similar to those of the changes in viscosity brought about by irradiation of the solutions. 3. Irradiation of solutions of purified rubber in an atmosphere of nitrogen does not bring about any change in their surface tensions, as judged by the values of the minima of their isotherms. 4. These facts show that, in the absence of oxygen, light may exert an independent effect on rubber by causing depolarization of the rubber molecules and disaggregation of the micelles, which is closely related to this depolarization. In a general way, the nature of the action of light on rubber and the conditions necessary for the light to be effective are explained by the present work. In conclusion, the authors wish to express their appreciation to Professor A. A. Seide for his kindness in furnishing the samples necessary for the work.