Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 25, 1998
Publication Date: N/A
Technical Abstract: Starch is a storage polysaccharide produced by plants. Major sources of starch are rice, corn, potatoes, and wheat. In its native form, starch is semicrystalline and isolated as granules whose size is dependent on plant source. Granule diameters range from approximately 1 micron (amaranth) to 30 microns or larger (potato); granules may be ellipsoidal, spherical, or polygonal, with varying degrees of surface roughness. Most starches are two component systems, comprised of two alpha-D glucose polymers: amylopectin and amylose. Amylose is lightly branched with molecular weights on the order of several hundred thousand, while amylopectin contains approximately 5% alpha 1-6 bonds and has molecular weights up to several hundred million. Since it is annually renewable, low cost, and inherently biodegradable, starch is an attractive raw material. The USDA has conducted research since the 1940s on the modification characterization nand use of starch in nonfood applications. In recent years, it has maintained a strong program in utilizing starch, both granular and thermoplastic, in biodegradable materials. This presentation focuses on recent developments in the use of granular starch in biodegradable thermoplastic composite materials. In particular, the effect of starch on transient state water sorption and diffusion and the role of granule- matrix adhesion on mechanical properties will be discussed. Maximum packing fractions of various starches and their blends, and implications for melt rheology and mechanical properties, will also be discussed.