Water vapor barrier and mechanical properties of paper-sodium caseinate and paper-sodium caseinate-paraffin wax films

A water vapor barrier and biodegradable packaging material was processed with paper, sodium caseinate (NaCAS) and paraffin wax. The water vapor barrier and the mechanical properties of coated paper were determined. In the first part of this work, the properties of the NaCAS-paper bilayers were investigated. The influence of the coating weight and the paraffin wax concentration was studied. The water vapor permeability (WVP) was decreased by increasing coating weight. Increasing the amount of wax in the coating led to a decrease in WVP. The tensile strength of the papers coated with NaCAS-paraffin wax emulsion was not affected by the coating weight. However, the elongation at break was increased by increasing coating weight. Tearing resistance was increased by increasing paraffin wax concentration. The second part of this work consisted of the study of the paper-NaCAS-paraffin wax three-layer films. The WVP was lowest for the three-layer material due to the hydrophobic character of the wax layer. Paper, which consists of a porous cellulose network, is often coated to improve its barrier properties to water vapor, oxygen and aromas. Natural polymers can be used as barrier coatings on paper packaging materials. Such coatings have the potential to replace current synthetic paper coatings. This study has shown that sodium caseinate coating improves paper strength and ductility. We also found that the greatest reduction in paper water vapor permeability is achieved by addition of a paraffin wax layer to the paper already coated with sodium caseinate. Both bilayer and emulsified coatings processed in this study have potential advantages for some food applications. They may be used as barriers to moisture transfer in food products. They have potential environmental advantages over conventional synthetic films. The use of these biodegradable coatings for packaging reduces waste disposal problems and reduces use of nonrenewable resources.