Effect of Ca 2+ induced crosslinking on the mechanical and barrier properties of cast alginate films

The use of alginate as a coating material for packaging applications is currently limited due to its difficult processability and high moisture sensitivity. Therefore, this study addresses the crosslinking and scale‐up to a continuous application. Three different crosslinking agents were applied: CaCl 2 with ethylene diamine tetraacetic acid and two low soluble salts (CaHPO 4 and CaCO 3 ). Those were incorporated by internal setting in an alginate matrix with varying Ca 2+ concentration ( c C a ) and ratio. With the addition of Ca 2+ , the tensile strength and elongation at break of the cast alginate films increased. This was optimal for ac C aof 0.010–0.015 g (g alginate) −1 dependent on the crosslinking agent. The decrease in water vapor and oxygen permeability due to crosslinking was independent of the crosslinking agent. However, the optimalc C aaiming to decrease permeability was different for the crosslinking agents: CaHPO 4 showed best results at ac C aof 0.010 g (g alginate) −1 , CaCl 2 at 0.012 g (g alginate) −1 , and CaCO 3 at 0.027 g (g alginate) −1 . Upon all analyzed properties CaHPO 4 was the most promising crosslinking agent for alginate. Moreover, selected alginate formulations were successfully processed in a continuous lacquering plant. The produced two‐layer systems have very low oxygen permeabilities which can be further reduced by crosslinking. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135 , 45754.