Solubility of Oxygen in Rubber and Its Effect on Rate of Oxidation

Abstract

Abstract It is apparent that an artificial aging test must consider the concentration of oxygen existing in the rubber. The concentration of oxygen in rubber suspended in air at 70° C. will be less than that required for normal oxidation at the maximum rate. This should limit the use of an air atmosphere to the highest quality of rubber in which the rate of oxidation is extremely small in comparison with the rate of diffusion of oxygen, and in this case tests should be confined to thin slabs. The solubility of oxygen in rubber suspended in oxygen at 70° C. and atmospheric pressure appears to be slightly greater than that required for uniform oxidation. Under these conditions thin slabs of good or medium-quality rubber should oxidize in a satisfactory manner. The fact that strips 4 mm. square of a rubber extremely sensitive to oxidation, when tested in an oxygen atmosphere at 26° C., produce deviation from a straight line would make doubtful the accuracy of tests conducted on easily oxidized rubber under these conditions. This type of rubber would require 2 or 3 atmospheres pressure in order to maintain the required oxygen concentration. The type of deterioration appearing at higher temperatures should have little influence unless high oxygen pressure is used. The use of both high temperature and high pressure may emphasize types of oxidation which are suppressed at ordinary temperature. Since little is known about this type of oxidation, it is believed that the simultaneous use of high temperature and high pressure should be avoided.