Submitted to: North American Thermal Analysis Society Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/15/2006
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.
Technical Abstract: In order to determine the degree of compatibility between PLA and different bio-materials (fibers), PLA was blended with sugar beet pulp, apple, cuphea, lasquerella, and milkweed fibers. Fibers were added at 85:15 and 70:30 PLA:Fiber. The composites were dry blended, extruded and injection molded. DSC ad TGA analysis of the extruded (EX) and the extruded-injection molded (EXIM) blends were performed. After melting in the DSC, composites were left for aging at room temperature for 0, 7, 15, and 30 days. Immediately after melting, samples were cooled by emersion in liquid nitrogen. Samples were heated from 15 to 180 degrees C at a 10 degrees C/min. The neat PLA showed a Tg at 59 degrees C and a 0.464 delta Cp. The glass transition was followed by a crystallization and melting transitions. The aged neat PLA exhibited 20% higher Tg and 10% higher enthalpic relaxation (ER) while crystallinity decreased by 9%. The Tg of the EX and the EXIM aged neat PLA samples showed similar values as the unprocessed PLA. The range of the difference in ER between the neat PLA and the EX and EXIM PLA was 0.353 J/g versus 1.202 J/g respectively indicating the effect of EX and EXIM on the physical properties of PLA. The percent crystallinity dropped by 95% on EX and by 80% for the EXIM. The drop was caused by the EX and EXIM process while EXIM showed lesser drop on the percent crystallinity. In the presence of fiber, 42% of the crystallinity was recovered where the percent crystallinity has increased from 4.4 to 13.2%. The percent crystallinity has increased as a function of fiber content, injection molding, and the aging time.