Structure and Properties of Composites Compression-Molded from Polyurethane Prepolymer and Various Soy Products

Abstract

A series of protein composites was successfully prepared from 30 to 50 wt % polyurethane prepolymer (PUP) with soy dreg (SD), soy whole flour (SWF), and soy protein isolate (SPI), by a compression-molding process at 120 °C without addition of any plasticizer. The structure and properties of the sheets were characterized by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermogravimetry analysis, dynamic mechanical analysis, tensile test, and biodegradability test. The results indicated that the −NCO groups in PUP reacted with −NH2, −NH−, and −OH groups in soy products to form a certain degree of grafting and cross-linking, showing a new glass transition temperature (Tg) at −32 to −25 °C, compared with raw materials. Moreover, the toughness, thermal stability, and water resistivity of the composite sheets significantly increased. By increasing PUP content, the elastomer materials blended PUP and soy protein could be ob...