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United States Department of Agriculture

Agricultural Research Service

Title: Properties of Extruded Foams from Starch/polymer Blends

Authors
item Willett, Julious
item Shogren, Randal

Submitted to: American Chemical Society Abstracts
Publication Type: Proceedings
Publication Acceptance Date: January 29, 2002
Publication Date: N/A

Interpretive Summary: Currently starch is used to produce loose-fill packaging foams ("peanuts") which can replace petroleum-derived plastic (polystyrene) foams. Most starch foams require modified specialty starches which increase cost relative to polystyrene. The potential for producing foams using lower cost, unmodified starches by blending with biodegradable plastics was examined. When blended at a starch/plastic ratio of 90/10, several foams made with unmodified corn starch had properties comparable to starch foams currently available. On the other hand, some of the starch-plastic blends gave foams which were not suitable for packaging applications. The starch-plastic foams were not as sensitive to water as foams of starch alone. These results indicate that starch-biodegradable plastic blends have the potential for use in foams, and highlight the need for a fundamental understanding of starch-based materials. This information will be useful to other scientists studying starch-based materials, and to manufacturers of packaging foams.

Technical Abstract: Starch was blended with various biodegradable polyesters and extruded into foams. Foam density, expansion, and compressive strength were measured. When poly (lactic acid) (PLA), poly (hydroxyester ether) (PHEE) or poly (hydroxybutyrate-valerate) (PHBV) were blended with corn starch, foam densities were significantly lower than the native starch. In general, the radial expansion of the starch/polyester blends was much greater than the native starch, while the specific length (cm/gm) was less affected. Blends with lower radial expansions than the control starch had greater specific lengths. Compressive strength depended only on foam density for the starch/polyester blends. Similar results were obtained when wheat, potato, or 70 percent amylose starches were blended with PLA and PHEE. Several other biodegradable polymers were also evaluated, but did not achieve the low densities and large expansions seen with PLA, PHEE, and PHBV.

Last Modified: 11/21/2014
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