Effect of additives on properties of cross‐linked carboxymethyl starch/polyvinyl alcohol composite films

Abstract In order to improve the comprehensive performance of cross‐linked carboxymethyl starch (CCMS)/polyvinyl alcohol (PVA) composite films, expand its application in the field of daily packaging. The CCMS/PVA blend films were prepared by solution casting method. The effect of environmentally friendly non‐toxic additives citric acid, urea, CaCl 2 , and nano‐SiO 2 on the microscopic surface morphology, crystallization properties, thermal properties, mechanical properties, water resistance and optical properties of the CCMS/PVA composite films were investigated. The biocomposite films were characterized by SEM, FT‐IR, XRD, TGA, tensile testing, water absorption test, water vapor transmission test, and UV–visible spectrophotometer. The result indicates that the compound addition of citric acid and urea greatly increase the elongation at break of the composite films from 9.2% to 225.7%. With the composite addition of citric acid and nano‐SiO 2 , the composite film has the best water resistance and water vapor barrier properties. The composite films added with citric acid, urea and nano‐SiO 2 can obtain the best thermal stability. Among these four additives, CaCl 2 has the largest negative effect on the elongation at break and urea has the largest negative effect on water resistance properties of the CCMS/PVA composites. The CCMS/PVA composite films prepared by adding 30% citric acid and 6% nano‐SiO 2 has the best comprehensive performance. The tensile strength, elongation at break, solubility, thermal decomposition temperature, water vapor permeability and light transmittance of the CCMS/PVA/CA/S composite films are 3.3 MPa, 168%, 34.6%, 293.2°C, 1.54 × 10 −11 g s −1 m −1 Pa −1 and 22.47%, respectively. The biocomposite film has the potential to be applied in the field of packaging, and provides a reference for further research.