Sorption and Permeation of Water and Water Vapor in Hydrophilic Polyamide, Poly (tetrahydropyran-2, 6-diyliminocarbonyl)

Abstract

Water sorption capacity of Poly (tetrahydropyran-2, 6-diyliminocarbonyl) [I] is about 3 times as high as those of nylon 6 and nylon 66 and almost the same order of that of wool. The sorption isotherm of I is independent of temperature. This suggests a large number of relatively weak polar sites are present in I. Water vapor permeability coefficient P of I is one order higher than that of cellophane membrane at high relative vapor pressure, and the relative vapor pressur dependence of P is smaller than the case of cellophane membrane. The activation energy of water vapor diffusion coefficient is relatively small, and is 7.6 and 4.1 kcal/mol at the relative vapor pressure 0.2 and 0.8, respectively. These values are close to that of water permeability, 6.9 kcal/mol. Above results suggest that the interaction between polar sites in I is relatively weak and the polymer has a relaxed structure.