Submitted to: North American Thermal Analysis Society Meeting
Publication Type: Abstract only
Publication Acceptance Date: 9/21/2005
Publication Date: 9/21/2005
Citation: Mohamed, A. 2005. Kinetics of poly(lactic acid) and transglutaminase-crosslinked wheat gluten blends [abstract]. North American Thermal Analysis Society Meeting. Paper No. 1. Interpretive Summary:
Technical Abstract: Wheat gluten (10g) was crosslinked (XL) using 10 units of transglutaminase in 2L of a 0.1M Tris-HCl buffer pH(7.5). The reaction lasted 24 hours at 40ºC. The suspension was then freeze-dried. Different blends of XL gluten and Poly(Lactic acid) (PLA) were prepared and mixed in a Brabender mixer at 180ºC for 10 min. Neat components and blended samples were tested using Modulated Differential Scanning Calorimetry (MDSC), where 40-50 mg of the sample were scanned from 20 to 250ºC with a 10ºC/min heating rate. The onset and peak temperatures and delta-H were recorded. Neat PLA displayed a glass transition (Tg) and exothermic (Cry) followed by endothermic (Mel) transitions. The plot showed a Tg of 0.46 Jg/ºC, a Cry of 29.9 J/g, while Mel exhibited 28.7 J/g. XL wheat gluten demonstrated one Tg with 0.45 J/g/ºC. Samples were subjected to repeated heating and cooling cycles in order to show the level of interaction between the two polymers. An isothermal DSC experiment was used to determine activation energy (Ea) and the pre-exponential factor (Z) (assuming reaction rate n=1) according to the Borchardt and Daniels (B/D) kinetics approach. The blends showed reduced 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 an increase in Ea. The Z value showed a significant increase in the presence of XL gluten, indicating a higher PLA molecular mobility.