WATER SORPTION FOR POLY(ACRYLONITRILE)/ POLY (ACRYLAMIDE) BLENDS AT LOW VAPOR PRESSURES

Abstract

The present work attempts to elucidate in detail the sorption properties of poly (acrylonitrile)/ poly (acrylamide) blends at low vapor pressures. The adsorption was measured with a volumetric water sorption apparatus similar to those widely used for surface area measurements. The results were compared with our previous results obtained by the weighing bottle method. It was found that the vacuum apparatus provided higher precision than the classical weighing bottle method, even under a relative vapor pressure, 0.1. The results obtained on the blends were compared with those on an acrylonitrile/acrylamide copolymer sample.
The sorption capacity of the blends was less than that of the copolymer at a relative vapor pressure, 0.2. This was attributed to the existence of strong hydrogen bond interactions between the amide groups in the blends. However, above a pressure, 0.3, the hydrogen bonds seemed to be no longer operative, probably due to the formation of the monolayer of adsorbed water. The total uptake of water by the blends could be taken as the sum of the individual uptakes of the blend components. This exact same behaviour was found at all pressures for the copolymer, the total uptake was the result of the linear additivity of the uptakes of the components.