The Effect of Citric Acid on Physicochemical Properties of Hydrophilic Carboxymethyl Starch-Based Films

Abstract

The carboxymethyl starch-based films in a presence of citric acid were prepared by casting technique. The influence of citric acid content on physicochemical properties of obtained hydrophilic films were evaluated (solubility in water, moisture absorption, mechanical and thermal properties). The crosslinking of starch derivative chains has been confirmed by FTIR spectroscopy, however, an excess of citric acid could cause hydrolysis of carboxymethyl starch chains. The best mechanical performance has been noted for the system containing 30 wt% (the highest tensile strength as well Young modulus 160 kPa and 650 kPa, respectively) as well as the highest Tg (ca. 58 °C). Additionally for the mentioned system the lowest solubility in water has been determined.