Swelling Effect of Liquids on NBR (Nitrile Rubber)

Abstract

Abstract Immersion tests in various polar and nonpolar solvents have been undertaken with a range of butadiene-acrylonitrile copolymers. For a particular liquid, it would appear that the volume change can be related to the acrylonitrile content of the rubber' by a Gaussian type curve which is described by three constants α, β and γ. The constant a corresponds to the nitrile content of the rubber which has maximum swelling in the liquid and would appear to be related in some way to the dielectric constant of that liquid. The constants β and γ control the value of maximum swelling. Investigation into the nature of the three constants tends to suggest that α and β are governed by molecular attraction due to the “dispersion forces”. On the other hand, γ seems to be connected with the electrostatic forces of attraction and is probably not a constant over the full range of nitrile content, but should be replaced by an expression governed by two other constants. Therefore, to describe the solvent power of a nonpolar solvent, two parameters are needed while four are required for a polar solvent.