Crosslinking of new elastomers functionalized with carboxyl groups

Abstract

The new carboxylated acrylonitrile-butadiene (XNBR) and styrene-butadiene (XSBR) rubbers produced were crosslinked with zinc oxide. The cure products are characterized by acceptable stress-strain properties. The increase in ZnO amount used, after exceeding of stoichiometric quantity with respect to -COOH groups content, does not improve the stress-strain properties. The curing of new XNBR and XSBR with ZnO leads to the formation of ionic crosslinks. An increase in swelling degree in toluene after action of NH3 vapors, capable to destroy the ionic bonds, confirms this conclusion. The best stress-strain properties of cured products were achieved when carboxylated rubbers were hybrid cured, e.g. using simultaneously zinc oxide and sulfur, in the presence of N-cyclohexyl-2-benzothiazolesulfenamide as vulcanization accelerator. The products of such crosslinking contain both ionic and sulfide bonds and are characterized by the tensile strength of 8 MPa in cured state.