THE EFFECT OF MONTMORILLONITE NANOCLAY ON MECHANICAL AND BARRIER PROPERTIES OF MUNG BEAN STARCH FILMS

Starch is an interesting biodegradable polymer due to its excellent film forming properties, availability, and low cost. On the other hand, starch films are often limited by their poor mechanical properties, and water resistance. The addition of montmorillonite clays have improved these properties in both petroleum and biodegradable films. The objective of the research was to determine the effect of montmorillonite clay on the mechanical and barrier properties on mung bean starch films. The addition of 5% clay yielded the optimum balance between mechanical and barrier properties of these composite films with improved tensile strength (TS) of 20.8763± 0.789 MPa, decreased water vapor permeability (WVP) to 0.49150 ± 0.0502 ng m/m2 sPa and decreased oxypen permeability (OP) to 5.84 ± 1.10 cc-mil/(m2-day). Clay levels above 5% improved water vapor barrier properties, with greatest results for 25 and 30% clay of 0.4519 ± 0.0603 and 0.4405 ± 0.0826, respectively. However, the films became brittle with the further addition of clay and had lower TS values and % elongation at break (EB) values. X-Ray Diffraction showed exfoliated clay microstructures for films with lower clay amount. Above 10% clay, intercalated montmorillonite clay layers and clay were obtained. TEM images confirmed the X-Ray results. The highest ultrasonification times of 30 and 60 minutes (5%wt clay) yielded the highest TS values, 20.6083 ± 1.330 and 20.4281 ± 1.355 MPa, respectively. Ultrasonification time had no effect on EB. Oxygen permeability decreased as ultrasonification time increased to minimum permeability of 2.36 ± 0.27 cc-mil/(m2-day). WVP decreased as ultrasonification time increased with the lowest value at 5 minutes ultrasonification of 0.5269 ± 0.0712 ng m/m2 sPa. The X-Ray results as well as the TEM images determined exfoliated structures for higher ultrasonification times of 30 and 60 minutes and intercalated structures for lower ultrasonification times