Structure and properties of soy protein plastics plasticized with acetamide

Acetamide-plasticized SPI sheets, denoted SAm, were prepared by compress molding at 140 degrees C and 20 MPa. The compatibility between acetamide and SPI has been investigated by DSC, WXRD, optical transmittance and SEM. Strong hydrogen bonding interaction between SPI and acetamide was,evidenced by FT-IR spectroscopy. When acetamide contents reached 30 phr the SAm exhibited best plasticity, leading to the highest elongation at break ('178%) of the material. Moreover, the single glass transition temperatures of the SAm sheets decreased with an increase of acetamide content. Furthermore, the results from torque rheology revealed that the flexibility and processability were improved when the acetamide contents increased from 10 to 50 phr. Interestingly the acetamide-plasticized SPI materials had better optical transmittance at 800 nm (75%) than that of glycerol-plasticized SPI sheet, indicating a good compatibility of the SAm materials. At the same time, the results from TGA measurement and the water uptake indicated that SAm sheets possessed higher thermal stability and water-resistance than those of glycerol-plasticized SPI. This work provided a good plasticizer for SPI, and it is anticipated to use in biodegradable protein materials widely. [GRAPHICS] Water uptake of the SAm sheets at 35% RH.