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

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°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/°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/°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. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007