DOW Graduate Seminars: Biodegradable Polymer Nano-composites

Event Date: February 12, 2008
Speaker: Dr. Leonard Uitenham
Speaker Affiliation: Department of Chemical Engineering, North Carolina A&T State University
Time: 3:30 - 4:30 pm
Location: FRNY G140

Increasing the use of biodegradable polymeric materials will help with the current landfill challenges facing the countries waste problem. Improving the mechanical properties of biodegradable polymers will increase their usage over traditional polymer/plastic materials. Biodegradable polymers, especially those relying on renewable resources, have attracted significant attention recently. Aliphatic polyesters such as polylactides encounter various applications due to their biodegradable and/or biocompatible character. Poly (lactic acid) (PLA) is produced from L-lactic acid that is derived from the fermentation of corn or sugar beet. Polymer nanocomposites based on biodegradable PLA and organically modified layered silicates were prepared by melt processing using a Brabender twin screw mixer. Several organically modified montmorillonite (Nanoclay) were incorporated at 1% loading level into the PLA.

An exfoliated morphology has been evidenced by X-ray diffraction analysis and Transmission Electron Microscopy (TEM) studies, for the combination of PLA and the natural montmorillonite modified with a quaternary ammonium salt namely Cloisite® 30B.

Further studies were done on the same combination with loading levels of 1%, 2%, 3%, 4% and 5%. Thermal stability of the nanocomposites was studied using the Thermogravimetric Analysis (TGA). An increase in thermal stability with the clay content was observed by TGA, with a maximum obtained for a loading of 3 wt% of 30B nanoclay. Glass transition and melting point data were collected and analyzed using the Differential Scanning Calorimeter (DSC). The onset of Tg has been increased by the addition of the 30B nanoclay. However it was observed that at higher loading levels there is a decrease in the thermal stability (above 2 wt% 30B) and the glass transition temperature (above 3 wt% 30B). Mechanical properties of the PLA nanocomposite have been found to increase against neat PLA.