VISCOSITY PREDICTION FROM A MODIFIED SQUARE-WELL INTERMOLECULAR POTENTIAL MODEL - POLAR AND ASSOCIATING COMPOUNDS

A theoretically based model for calculating both liquid and gas phase viscosities has been developed by modifying a statistical mechanics vi scosity model based on the square well intermolecular potential. The o riginal theory was corrected to account for the assumptions of only tw o-body interactions and molecular chaos for velocities and the inadequ acy of the square well potential. In addition, the model was modified so that it approaches a consistent low density limit and to improve th e dilute gas temperature dependence. The three model parameters are ob tained from gas and liquid viscosity data and generalized with group c ontributions. With the resulting modified square well viscosity model, gas and liquid viscosities for a wide variety of over 100 polar and h ydrogen bonding compounds are correlated with average deviations of 0. 4% (gas) and 2.1% (liquid), and predicted with average deviations of 2 .1% (gas) and 6.8% (liquid). (C) 1997 Elsevier Science B.V.