|Lawton Jr, John|
Submitted to: Annual Meeting of the Bio Environmentally Degradable Polymer Society
Publication Type: Abstract Only
Publication Acceptance Date: 8/17/1999
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Thermoplastic starch was blended with a hydroxy-functional polyester, which is biodegradable and has superior barrier and tensile properties. These thermoplastic polyesters with pendant hydroxyl groups are prepared by the reaction of diacids and diglycidyl ethers using quaternary ammonium halide salts as initiators. The particular polyester used in this work is derived from bisphenol A and adipic acid and is referred to as poly(hydrox ester ether)(PHEE). It is an amorphous material with a glass transition temperature (Tg) of 45 deg C in the dry state. The effect of moisture content of the starch phase, temperature, and shear rates on the melt flow behavior and the resulting morphology of the blends was studied. The critical role played by the ratio of the viscosities of the two polymers was examined. The viscosity ratio was found to vary over two orders of magnitude (0.1-10) with relatively small changes in the moisture content (15-30%) and temperature (120-160 deg C). This had a profound effect on the level of mixing, nature of dispersion, and the onset and nature of co-continuity. Deformation (in the flow direction) of the dispersed phase was possible under high moisture conditions, leading to fibrillar and laminar types of morphologies at 50-80% starch level, whereas processing at a low moisture level produced a more dispersed morphology. When the viscosities of the two phases were significantly different, it was observed that the low viscosity polymer had a tendency to enrich the surface. The presence of hydrophobic PHEE would be valuable in designing products with reduced permeability to water vapor. This research was conducted under CRADA No. 58-3K95-8-0634 between Agricultural Research Service (ARS) and Biotechnology Research and Development Consortium (BRDC).