| Three kinds of water-borne polyurethane were selected to prepare blend films with silk fibroin, namely SF/PU blend films. The conditions and methods of preparing films were investigated. The structure of blend films at different blend ratios was studied by means of X-ray diffraction, FTIR spectra, differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The morphology of the blend films and the distribution of the two components were observed with scanning electronic microphotograph (SEM), and the strength and elongation at break, initial tensile modulus, compressibility, water-vapor permeability and the weight loss rate of silk fibroin in blend films were determined. The results of both X-ray diffraction and FTIR spectra showed that there somehow existed some mutual influence between the two components in SF/PU blend films, which induced the formation of Silk II in blend films, and the result of thermal analysis indicated that the thermal stability of silk fibroin in the blend films was improved, which was attributed to the addition of polyurethane. It was showed in the SEM that the morphology of blend films at different blend ratios was different apparently, and the film at blend ratio of 50 to 50 displayed a relatively even and delicate morphology. With the increase of polyurethane percentage in blend films, the broken strength, the initial tensile modulus and the compression linear rate decreased and the elongation at break increased. The water-vapor permeability and the weight loss rate of silk fibroin varied in a downward order of 75/25, 25/75 and 50/50 (SF/PU in blend film).
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