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United States Department of Agriculture

Agricultural Research Service

Title: Processing Effects in Starch Extrusion

Author
item Willett, Julious

Submitted to: Woodfiber Plastics Composites Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 27, 1996
Publication Date: N/A

Interpretive Summary: Starch is an attractive material for use in biodegradable plastics, because of its low cost and inherent biodegradability. The primary method of converting starch into useful plastic materials is extrusion. Extrusion subjects the starch to high temperatures and high pressures, which can cause degradation of the starch. In this work, extrusion effects on starch were studied. It was found that conditions of high pressure at lower temperatures could completely melt the starch. Higher temperatures also melted the starch, but at high extruder speeds some of the starch granules remained intact. In another aspect of this work, it was found that when starch was extruded at high speed during a second extrusion step, there was less degradation than at low speed. These results show that extruder design and operating conditions are critical in starch conversion. Knowledge of starch degradation during extrusion is important to researchers in the area of starch utilization in biodegradable plastics, since the degree of degradation during extrusion significantly impacts the properties of the starch-based material.

Technical Abstract: There has been considerable interest in the use of starch in biodegradable plastic applications in recent years, with particular emphasis on thermoplastic starch. Thermoplastic starch results from the disruption of the native granule structure induced by the temperature, shear, and pressure generated during extrusion. Process parameters including moisture content, screw speed, screw configuration, temperature, and additives significantly influence the rheological and structural properties of thermoplastic starch. This paper discussed the impact of several of these variables on thermoplastic starch.

Last Modified: 11/23/2014
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