THERMAL PROPERTIES OF EXTRUDED-INJECTION MOLDED POLY (LACTIC ACID) AND FIBER BLENDS

Authors: Mohamed, Abdellatif; Finkenstadt, Victoria

Submitted to: North American Thermal Analysis Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2006
Publication Date: 8/9/2006
Citation: Mohamed, A., Finkenstadt, V.L. 2006. THERMAL PROPERTIES OF EXTRUDED-INJECTION MOLDED POLY (LACTIC ACID) AND FIBER BLENDS. North American Thermal Analysis Society Meeting. xx.

Interpretive Summary:

Technical Abstract: Wheat gluten (10 g) was crosslinked (XL) using 10 units of Transglutaminase in 2L Tris-HCl buffer (pH 7.5). The reaction lasted 24 hrs. at 40ºC and 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 PLA components and blends were tested using Modulated Differential Calorimetry (MDSC), where 40-50 mg of sample were scanned from 20 to 250ºC with 10ºC/min. heating rate. The onset or peak temperatures and '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 J/g/ºC, Cry with 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. Isothermal DSC experiment was used to determine activation energy (Ea) and pre-exponential factor (Z) (assuming reaction rate n=1) according to 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. Higher number of cycles caused increase in Ea. The Z value showed a significant increase in the presence of XL gluten indicating higher PLA molecular mobility.