Test of the Applicability of Dielectric Loss Measurements to the Study of the Aging of Pure-Gum Rubber Mixtures
Abstract The measurement of the dielectric properties at radioelectric frequencies requires a technique and apparatus which are too delicate to serve at the present time as a practical test of the aging of vulcanized rubber. On the other hand, from the viewpoint of research, the dielectric method should furnish valuable data on the way in which oxygen tends to combine with rubber according to the particular conditions of aging. Thus, it has been found in aging tests of three different types of vulcanizates containing no protective agent that there is an increase of polarity, which is in some cases great, an increase of the dielectric viscosity, and a broad distribution of polar groups, formed by oxidation, between the different types of structures. The dielectric absorption leads in particular to the same classification of vulcanizates as do the classic methods of measuring oxidizability and decrease of tensile strength. Finally, in addition, measurement of the dielectric absorption makes possible the estimation at a high level of sensitivity of the degree of polarity of oxidation products.