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.