Study of the influences of film processing conditions and glycerol amount on the water sorption and gas barrier properties of novel sodium caseinate films

Water sorption and thermal properties of blown films prepared for glycerol contents varying from 15 to 25 wt% are then studied for a wide range of relative humidity. The determination of the water sorption isotherms and their modeling by Park׳s equation as well as the study of the water sorption kinetics parameters allow discussing the sorption mechanisms as a function of the respective plasticizing effect of glycerol and water, on one hand and of the ability of water molecules to form clusters within the material, on the other hand. The decrease of the glass transition temperature values of the films as a function of increasing water content is analyzed thanks to Gordon-Taylor equation and it is related to the respective plasticizing role of glycerol and water, as evidenced from water sorption analysis.