EVOH-based nanocomposites prepared by simple saponification method

The nanocomposite powders of poly(ethylene-co-vinyl alcohol)/Na+-montmorillonite (EVOH/MMT) and EVOH/Loess were prepared by a solution-precipitation and saponification method. EVA/toluene/nanoclay suspensions were precipitated and saponified in ethanol/KOH solution in a heterogeneous manner. Tensile properties, morphology, and thermal behavior of the prepared nanocomposites have been evaluated using UTM, SEM, and DSC, respectively. The tensile strength and elongation at break of EVA/MMT-50% and EVA/Loess-50% nanocomposites were significantly increased up to 1 h saponification time and thereafter gradually decreased. At 1 h saponification time, the tensile strength of EVA/ Loess-50% nanocomposite was increased by 5.4-fold to 14.7 MPa, whereas EVA/MMT-50% increased the tensile strength by 2.2-fold to 10.4 MPa compared to the un-saponified one. With the increase in saponification time, melting and crystallization peak temperature of both nanocomposites was shifted at a higher temperature. The antibacterial activity of saponified EVA/MMT-50% and EVA/Loess-50% powders was also determined by shake flask test against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Among the nanocomposites used in this study, EVA/MMT-50%-6 h exhibited strong antibacterial activity against the two kinds of bacteria.