Abstract:

Soy protein and formamide were mixed at different ratios and were hot press-molded to produce soy protein plastic. The properties ， structure and morphology of the plastic were then investigated by means of tensile test ,thermogravimetric analysis , dynamic mechanical thermal analysis , Fourier-transform infrared spectroscopy , and scanning electron microscopy. The results show that (1) the soy protein plastic with a formamide content (mass
fraction) of 20% has a maximum elongation of 269. 66% , which is 77 times that of pure soy protein plastic; (2) the temperature for the maximum mass loss of the plastic with 20% of formamide is much higher than the boiling point of pure formamide; and (3) the water absorption and glass transition temperature of the formamide-plasticized plastic decrease with the increase in formamide content , while the height of loss peak increases. It is also indicated by FTIR that there exist hydrogen bonds between the plasticizer and the soy proteins , which breaks the hydrogen bonds among the protein molecules. Furthermore , the SEM results prove that the introduction of formamide can greatly improve the microstructure and flexibility of soy protein plastic.

Key words: soy protein, forτnamide, plastic, plasticizer, property, structure