Rheology of Poly(acrylic acid) in Water/Glycol/Salt Mixtures

Abstract

Aqueous mixtures of 1,2-propylene glycol with added poly(acrylic acid), neutralized and with added salt, are used for aircraft deicing. This study reports data on the effects of varying the salt concentration, architecture, and temperature of a series of different mixtures. For a deicing fluid to be effective, it is desirable that it be able to create a liquid layer that is stable under low-shear conditions yet can be completely removed during the initial stages of takeoff. A number of the mixtures examined show a viscosity profile that is either almost independent of temperature or exhibits a peak. To gain a greater understanding of the factors responsible for the observed rheological behavior, a theoretical model was fitted to oscillatory data. Using two fitting parameters, it was possible to describe the changes in the observed behavior, suggesting that, as the temperature is varied, the extent of shielding of carboxylic acid groups and the conformation of the chain balance one another to give an apparent temperature independence of the viscosity. The rheological data were used to interpret the boundary-layer displacement thickness data obtained from wind-tunnel measurements.