ARS | Publication request: Thermal and Kinetic Properties of Poly (Lactic Acid) and Transglutaminase-Crosslinked Wheat Gluten Blends

Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 26, 2007
Publication Date: June 18, 2007
Citation: Mohamed, A., Xu, J. 2007. Thermal and kinetic properties of poly (lactic acid) and transglutaminase-crosslinked wheat gluten blends. Journal of Applied Polymer Science. 106(1):214-219.

Interpretive Summary: The main objective of this work is to develop new uses for excess agricultural products. The nature of interactions between natural and synthetic polymers (components) in different systems is not addressed adequately in the literature. The key to understanding these interactions is to understand the effect of these polymers on each other. The interaction between proteins and plastics is the determining factor that governs the use of proteins and other components in different biodegradable plastic formulas. This project is designed to produce a blend of agricultural products (i.e., soy proteins) and by-products (corn, and wheat proteins) with plastic material to produce biodegradable blends. The major benefits of this project are economical and environmental.

Technical Abstract: 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 180ºC for 10 min. Neat PLA and blends were analyzed using Modulated DSC (MDSC). Neat PLA displayed a glass transition (Tg) and exothermic (Cry) followed by endothermic (Mel) transitions. The profile showed a Tg of 0.46 J/g/ºC, Cry with 29.9 J/g, while Mel exhibited 28.7 J/g. XL wheat gluten displayed one Tg with 0.45 J/g/ºC. Samples were subjected to repeated heating and cooling cycles in order to show the level of compatibility between the two polymers. The activation energy (Ea) and pre-exponential factor (Z) were determined according to Borchardt and Daniels (B/D) kinetics approach. The blends showed increased Ea values with an increase in the amount of XL gluten. In the presence of 5% and 20% XL gluten, the Ea of PLA increased from 150 to 200 (kJ/mol) respectively. A higher number of cycles caused increase in Ea.