Rubbers Obtained from Butadiene Derivatives

Abstract

This chapter deals with rubbers which are produced by the polymerisation of substituted butadienes. There are only two families of such rubbers which are of commercial importance at the present time. These are the rubbers which are obtained by the polymerisation of isoprene and of chloroprene respectively. These two types of rubber are rather disparate as regards nature, technology, and areas of application. Isoprene rubber is a general-purpose hydrocarbon rubber which is intended as a competitor primarily for natural rubber, and to a lesser extent for styrene-butadiene rubber and butadiene rubber. Chloroprene rubber, on the other hand, is a special-purpose rubber which is used in applications which call for such attributes as moderate resistance to swelling in hydrocarbon oils, resistance to heat, and resistance to the action of ozone. Nevertheless, it is convenient and appropriate to consider these two rubbers together, in order to demonstrate how dissimilar two formally-similar rubbers can be. Chloroprene can be regarded as being derived from isoprene by replacing the methyl group of the latter by a chlorine atom, an atom which has almost the same size as the methyl group. Although the one monomer is derived from the other by a very simple substitution, the two rubbers derived from these monomers are very different, as the following pages will show. The origin of these differences is to be found in the electronegativity of the chlorine atom relative to that of the methyl group.