Improving the physical properties of starch and starch - carboxymethyl cellulose composite biodegradable films

Starch is the most abundant carbohydrate biopolymer that has excellent film-forming properties. But poor resistance to water vapour transport and poor mechanical properties are of its main problems. In this study a series of corn starch films with varying concentrations (0–20 %W/W) of citric acid and carboxymethyl cellulose (CMC) were prepared by casting method at 60˚C. The effects of citric acid on water vapor permeability (WVP)، moisture absorption، solubility and mechanical properties were investigated. The WVP decreased from 4. 63 to 2. 61×10-7 g/m. h. Pa as the citric acid percentage increased from 0 to 10%W/W. When the citric acid content of the films reached to 20%W/W، WVP increased about 15%. Moisture absorption and mechanical properties exhibited similar trends. In the presence of 10% citric acid، the introduction of CMC improved the moisture resistance of the composites. Using of 20%W/W CMC in the formulation increased ultimate tensile strength (UTS) by more than 59% compared to neat starch film. However، by increasing of the CMC concentration، the strain to break (SB) did not reduce significantly.