Soluble and Insoluble Rubber

Abstract

Abstract A particularly striking property of unvulcanized rubber is that benzene-soluble rubber, which is a colloid capable of unlimited swelling, is transformed on standing into insoluble rubber—a colloid of limited swelling capacity. Scarcely any difference in composition can be found analytically between the two kinds of rubber, which differ so widely in solubility. Insoluble rubber can be reconverted into a soluble form by long standing or by mastication. These apparently reversible transformations between soluble and insoluble rubber were formerly ascribed to a micellar structure of rubber; it was assumed that the swelling phenomena, as also the high viscosity of rubber solutions, were connected with the solvation of the micelles. In contrast to such micellar theories it was shown, by the conversion of polymer-homologous rubbers into the polymer-analogous hydrorubbers, that the colloidal particles in dilute solutions are the macromolecules themselves. The high viscosity of rubber solutions is caused by the thread-like form of the macromolecules and not by a micellar structure; rubber thus belongs to the linear molecular colloids.