SORPTION AND TRANSPORT OF WATER-VAPOR IN NYLON 6,6 FILM

The sorption and transport of water in nylon 6,6 films as functions of the relative humidity (RH) and temperature were studied. Moisture-sor ption isotherms determined gravimetrically at 25, 35, and 45 degrees C were described accurately by the GAB equation. Water-vapor transmissi on rates were enhanced above approximate to 60-70% RH, primarily due t o the transition of the polymer from glassy to rubbery states. The gla ss transition temperatures (T-g's) of nylon 6,6 were measured at vario us moisture contents using differential scanning calorimetry. The resu lts showed that the sorbed water acted as an effective plasticizer in depressing the T-g of the polyamide. Fourier transform infrared spectr oscopy (FTIR) was utilized to characterize the interaction of water an d the nylon. Evidence from FTIR suggested that the interaction of wate r with nylon 6,6 took place at the amide groups. Based on the frequenc y shift of the peak maxima, moisture sorption appeared to reduce the a verage hydrogen-bond strength of the N-H groups. However, an increase was seen for the C=O groups. (C) 1999 John Wiley & Sons, Inc.