Structure and Properties of Poly (Vinyl Alcohol)/Soy Protein Isolate Blend Film Fabricated Through Melt Processing

Abstract

Poly (vinyl alcohol) (PVA)/soy protein isolate (SPI) blend film plasticized with glycerol is fabricated by melting processing in presence of water. The structure and properties are investigated by Fourier-transform infrared spectroscopy, X-ray diffraction, differential scanning calorimeter, scanning electron microscope (SEM), mechanical testing, and thermo-gravimetric analysis (TGA). It is found that strong hydrogen bonds between soy protein and PVA macromolecules are formed. The incorporation of soy protein into PVA decreases the crystallinity of the latter. The crystallization and melting temperatures decrease with increasing SPI content. SEM shows that certain degree of phase separation occurs in the blend film, with soy protein phase finely dispersed in the PVA matrix. The PVA/SPI blend film possesses high flexibility even at high protein content, which ensures its potential applications as packaging film. TGA experiments shows that the incorporation of soy protein rendered the thermostability of the blend film.