Systematic investigation on the swelling behaviors of acrylonitrile-butadiene rubber via solubility parameter and Flory-Huggins interaction parameter

Three-dimensional solubility parameters (HSP) of the acrylonitrile-butadiene rubber (NBR) were determined by combining a software program with equilibrium swelling test. Then, a modified Flory-Huggins interaction parameter (chi(HSP)) was calculated and compared with the traditional one (chi) in characterizing the swelling behavior of NBR. NBR exhibits quite different swelling responses in the selected seven kinds of organic solvents, which can be differentiated by the energy difference (Ra) and be further correlated with chi(HSP) value between rubber and solvent. The results turn out that the swelling ratio (q) decreases with increasing chi(HSP) value. By mathematical fitting, an exponential relationship between q and chi(HSP) is achieved to predict the swelling behaviors of NBR in the increasing used bio-fuels, bio-diesel, and IRM903 being selected for examples. From the prediction model, we can get that there is a high swelling area for bio-diesel/ethanol system and both a high and low swelling areas for IRM903/ethanol system. Hereby, it is expected that the swelling behavior or oil resistance of NBR based rubber parts can be predicted quantitatively in a concise way now.