Thermal and kinetic properties of poly(lactic acid) and transglutaminase-crosslinked wheat gluten blends

摘要

Wheat gluten (10 g) was crosslinked (XL) using 10 units of transglutaminase. Different blends of XL gluten and poly(lactic acid) (PLA) were mixed in a Brabender mixer at 180 degrees C for 10 min. Neat PLA and blends were analyzed using modulated DSC (MDSC). Neat PLA displayed a glass transition (T-g) and exothermic (Cry) followed by endothermic (Mel) transitions. The profile showed a T-g of 0.46 J/g/degrees C, Cry with 29.9 J/g, whereas Mel exhibited 28.7 J/g. XL wheat gluten displayed one T-g with 0.45 J/g/degrees C. Samples were subjected to repeated heating and cooling cycles to show the level of compatibility between the two polymers. The activation energy (E-a) and pre-exponential factor (Z) were determined according to Borchardt and Daniels (B/D) kinetics approach. The blends showed increased E-a values with an increase in the amount of XL gluten. In the presence of 5 and 20%, XL gluten, the E-a of PLA increased from 150 to 200 kJ/mol, respectively. A higher number of cycles caused an increase in E-a. The T-g temperature of different PLA/XL gluten blends can be predicted by Gordon-Taylor equation and its modified forms. (c) 2007 Wiley Periodicals, Inc.