THE SORPTION OF WATER-VAPOR BY AN AMORPHOUS POLYAMIDE

A modified dual-mode sorption model represents the sorption of water vapor by an amorphous polyamide at 23-degrees-C. The Langmuir equation is used to calculate the volume fraction of chemisorbed solute and the Flory-Huggins equation is used instead of Henry's law to calculate the volume fraction of water which is not chemisorbed. This model describes the data over a range of water activities from zero to one and predicts clustering of the sorbant. Fourier Transform Infrared (FTIR) spectroscopy data and dielectric measurements of the gamma relaxation temperature suggest that the water associates with amide groups at low water activities.