Purified Rubber for Electrical Insulation
Abstract THE water absorption and the dielectric stability of soft rubber insulating compounds under wet conditions is influenced by the kind of crude rubber employed. For most rubber-covered aerial and building wire where moisture conditions are not severe, the better grades of plantation rubber are satisfactory. However, for service involving immersion for long periods in fresh water, a need exists for rubber containing less nonhydrocarbon water-absorbing substances than the plantation product. This is particularly true when the insulating wall is thin and a high degree of electrical stability is required. Only recently has the preparation of such a type of purified rubber been given serious consideration on the plantations in the Far East. In the past, coöperation on such a problem with the plantation has been difficult, and for that and other reasons methods have been developed here for preparing this rubber in the factory. The purpose of this paper is to discuss the nature and role of protein and other substances found in Hevea rubber and to outline various methods for purifying rubber. Data are presented on the composition and properties of the resulting products.