Effect of equilibrium moisture content on barrier, mechanical and thermal properties of chitosan films

Water molecules modify the properties of biodegradable films obtained from hydrophilic materials. Moststudies dealing with thermal, mechanical and barrier properties of hydrophilic films are carried out underone relative humidity (RH) condition. The objective of this work was to evaluate the effect of the moisturecontent on the thermal, mechanical and barrier properties of chitosan films under several RH conditions.Microclimates, obtained with saturated salt solutions were used for conditioning samples and theproperties of the films were evaluated under each RH condition. Chitosan films absorbed up to 40% ofmoisture at the higher RH studied. The percentage of elongation and the water vapour permeabilityincreased while tensile strength, Young?s modulus and glass transition temperature decreased, whenthe moisture content increased. The results suggest that the water molecules plasticized the polymermatrix, changing the properties when the films were in contact with high RH environments.