Reaction of Bromine with Rubber in Aqueous Suspension and Its Analytical Use

Abstract

Abstract The rubber hydrocarbon is considered to consist of the combination of an indeterminate number of C5H8 or isoprene units. In this unit there is a double bond capable of adding two atoms of bromine. This addition takes place with pairs of C5H8 groups, with formation of the tetrabromide C10Hl6Br4. Under certain conditions the compound C10H15Br5 is formed, in which case bromine replaces one atom of hydrogen and, at the same time, hydrogen bromide is liberated. The direct determination of the hydrocarbon of rubber by its transformation into the tetrabromide has been utilized by various investigators. Rubber dissolved in benzene, chloroform, or carbon tetrachloride is treated with a solution of free bromine and carbon tetrachloride. The tetrabromide which is formed is separated and weighed. The volumetric determination of the rubber hydrocarbon by bromine is generally impaired by the action of the bromine on the solvent and on the impurities which are present in the rubber. We have tried to study in this work the combination of bromine with rubber in aqueous dispersion, particularly in latex, by an indirect method, based on accepted definitions of the dry rubber content and the total dry residue. The bromine is used in the form of a mixture of bromate and bromide in the presence of acid, and the excess is determined volumetrically. In this way, a bromination factor is obtained, which represents the quantity of bromine consumed per unit of rubber.