Characteristics of soy protein isolate-montmorillonite composite films

Soy protein isolate/montmorillonite (SPI/MMT) nanocomposite films were prepared in which MMT was used as a nanofiller at 0, 3, 6, 9, 12, and 15 wt % relative to SPI dry weight. Effects of MMT on film properties including tensile strength, elongation at break, total soluble matter, water vapor permeability, and oxygen permeability were assessed. X-ray diffraction patterns were determined, and morphologies of SPI and the SPI-MMT composite films were visualized by scanning electron microscopy. Mechanical and barrier properties were improved by evidenced increases in tensile strength and modulus, and decreases in permeability to water vapor and oxygen. MMT concentrations of 3%-12% were optimal for improving functional properties of the composite films. X-ray diffraction and scanning electron microscopy examinations revealed the formation of an intercalated and exfoliated structure on the addition of MMT into the SPI matrix. We conclude that intercalated and exfoliated MMT silicates enhance mechanical and barrier properties of SPI films.