Journal of Polymer Science Part B: Polymer Physics, Vol.37, No.7, 691-699, 1999
Water absorption in EVOH films and its influence on glass transition temperature
Moisture sorption kinetics of nonoriented ethylene vinyl alcohol copolymer (EVOH) film (EF-E15) were studied at 25, 35, and 45 degrees C. Anomalous diffusion was observed for the polymeric film at high relative humidities (RH) and higher temperatures. Diffusion and solubility coefficients of water were found to be concentration dependent. The moisture sorption isotherms of three types of EVOH films (EF-E15, EF-F15, and EF-XL15) determined at 25, 35, and 45 degrees C, were well described using the GAB equation. Glass transition temperatures (T-g) of the EVOH films, as influenced by RH, were measured using differential scanning calorimetry. T-g values decreased with increasing RH due to the plasticization effect of water, and were found to be dependent on ethylene content and orientation of the EVOH films.