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Preparations and properties of biodegradable polymers from starch acetate and starch acetate -maleate mixed esters
Starch is a well-known candidate material for replacement of petroleum-derived synthetic polymers to decrease environmental pollution due to its low cost, availability, and total degradability after usage. However, weak water-resistance and poor mechanical properties and dimensional stability limit its wide application. High degree of substitution (DS) starch acetate and starch acetate-maleate are alternatives. ^ During acetylation, DS increased with longer reaction times and higher ratios of acetic anhydride to starch. Reaction efficiency increased with longer reaction times, and decreased with increases in the ratio of acetic anhydride to starch. After acetylation, and as DS increased, the crystalline structures and granule structures of native starch disappeared, while thermal stability increased. ^ Foams were prepared by extruding starch acetate with different DS values using water or ethanol as the blowing agent. Physical and mechanical properties, morphology, and water absorption of the foams depended on the type of blowing agent and DS. When extruded with water, the extrudates had dense cells with thick cell walls. Radial expansion ratio and spring index decreased, while unit density and compressibility increased with increasing DS. Contrary results were obtained with ethanol as the blowing agent. Tg and the thermal stability of foams increased with extrusion. The rate of biodegradation of the foams decreased with increasing DS. ^ Mixing with other biopolymers or preparation of starch acetate nanocomposites are two methods to improve functional properties of starch acetate foam. Good compatibility and functional properties of starch acetate/poly (tetramethylene adipate-co-terephthalate) (EBC) composite foams were observed with addition of a small amount of EBC. Higher amounts of EBC in the blends decreased the miscibility of these two polymers. ^ Starch acetate nanocomposite foams were successfully prepared by melt-intercalation with four nano sized organoclays with different polarities. Thermal behavior and mechanical properties increased with the addition of organoclay. ^ For starch acetate-maleate mixed esters, the characteristic peaks in 1H-NMR, 13C-NMR, and FTIR spectra indicated the presence of acetyl and maleate groups on starch molecules. ^
Agriculture, Food Science and Technology
Xu, Yixiang, "Preparations and properties of biodegradable polymers from starch acetate and starch acetate -maleate mixed esters" (2005). ETD collection for University of Nebraska - Lincoln. AAI3176810.