Preparation and evaluation of the barrier properties of cellophane membranes modified with fatty acids

Cellophane (regenerated cellulose) membranes with tailored properties regarding hydrophobic character and barrier effects were prepared by their controlled heterogeneous esterification with two fatty acid derivatives (hexanoyl and dodecanoyl chlorides). The characterization of the modified membranes was performed by FTIR spectroscopy, X-ray diffraction, and thermogravimetry, confirming the success of the heterogeneous modification reaction while keeping cellophane membranes structural properties. Contact angle measurements clearly confirm the enhanced hydrophobic character displayed by the modified cellophane membranes. The evaluation of their barrier properties was carried out by determining the permeability towards water vapor at different relative humidities and the permeability towards nitrogen, oxygen and carbon dioxide, using the time-lag method, in both wet and dry states. A decrease in both the water permeation and the permeability towards these gases in the wet state was observed for the modified membranes. No significant differences in behavior were found between the membranes prepared with hexanoyl and dodecanoyl chloride regarding hydrophobicity but the different lengths of the chain allowed a fine tune of the permeability. The obtained cellophane membranes are a good example of the development of new bio-based materials with improved surface and barrier properties.