Development of soy protein isolate/waterborne polyurethane blend films with improved properties

In the present work, poly(butylene adipate) (PBA) based waterborne polyurethane (WPU) was used for the first time to mix with soy protein isolate (SPI) to fabricate blend films. The effects of WPU content on the structure and properties of the resultant films were investigated by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) analyses. Strong intermolecular interactions were observed to exist between SPI and WPU, which played an important role in forming a homogeneous structure of the blend film. Moreover, the incorporation of WPU improved the water resistance and mechanical properties of SPI films, which suggested that the blend films might be used as food packaging, coating and biomedical materials instead of synthetic polymer materials.