A comparative study of the effects of starch, glycerol, and clay contents on the morphological and mechanical properties of corn starch nanocomposite films

In the present study, biodegradable starch films were prepared using the casting method with varying concentrations of corn starch (4.5 to 7.5% w/w), glycerol (20 to 40%), and sodium montmorillonite (NaMMT) (0 to 25% w/w), based on the amount of dry starch. The morphology of the corn starch-based films was investigated using optical microscopy and confocal scanning electron microscopy. ANOVA results indicated that the tensile strength of the corn starch-based films was significantly affected by the starch, glycerol, and clay content, as well as by their interactions. Statistical analysis showed that the highest tensile strength values were obtained for the films with high starch content. The interaction between starch and glycerol revealed that films with low glycerol content and high starch content exhibited better tensile strength properties. The mechanical properties of the films were further enhanced by the incorporation of NaMMT, even at lower montmorillonite clay content. The interaction between starch and NaMMT indicated an increase in tensile strength with higher clay content. Microscopic examination revealed a uniform distribution of clay particles within the starch film matrix. The best mechanical properties were observed in the nanocomposite films containing starch concentrations of 6.5 to 7.5% w/w, glycerol concentrations of about 20-40% w/w and a NaMMT clay content ranging from 10 to 15% w/w.