The role of defective structures of butadiene-nitrile elastomers in interphase interactions in mixtures with ethylene-propylene-diene rubbers

Abstract

The deviation of the equilibrium degree of swelling of nitrile-butadiene and ethylene-propylenediene rubbers (NBR and EPDM, respectively) in the selective n-heptane solvent (the Zapp method) from the additive values, which characterizes the density and volume of the interphase layer, was determined. This quantity was correlated with the free volume fraction in the defects of the NBR structure formed by acrylonitrile units and stereoirregularities of the butadiene copolymer. The increase in the free volume fraction in the defects calculated from the individual contribution of each structural unit favors the formation of a more developed interphase layer, whose density and volume also depend on the content of flexible ethylene units in EPDM and the degree of isotacticity of the propylene sequences.