Extruded foams prepared from high amylose starch with sodium stearate to form amylose inclusion complexes

Authors: Finkenstadt, Victoria; Felker, Frederick; Kenar, James - Jim; Fanta, George; Selling, Gordon; Hornback, Kathy; FISK, DONALD - Rolla National Bio-Polymers, Llc

Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2015
Publication Date: 4/5/2016
Citation: Finkenstadt, V.L., Felker, F.C., Fanta, G.F., Kenar, J.A., Selling, G.W., Hornback, K.J., Fisk, D.L. 2016. Extruded foams prepared from high amylose starch with sodium stearate to form amylose inclusion complexes. Journal of Applied Polymer Science. 133(13). doi: 10.1002/app.43251.

Interpretive Summary: Use of non-biodegradable plastics to produce foam packing materials has resulted in the build-up of large amounts of these materials in our landfills. Because of this problem, there has been an increased interest in the preparation of these foams from environmentally friendly materials that are inexpensive, readily available, and biodegrade rapidly, such as corn starch. Although a number of investigators have prepared foams from starch, starch-based foams will absorb water rapidly, and will soften, shrink, and loose their cushioning properties under high moisture conditions. In our current study, we have discovered that these undesirable properties of starch-based foams can be greatly reduced by adding small amounts of an inexpensive, environmentally friendly fatty acid salt to the starch when the foams are being produced. This results of this research will provide the manufacturer with an inexpensive method for tailoring the properties of these biodegradable forms for specific end-use applications.

Technical Abstract: Starch foams were prepared from high amylose corn starch in the presence and absence of sodium stearate and PVOH to determine how the formation of amylose-sodium stearate inclusion complexes and the addition of PVOH would affect foam properties. Low extrusion temperatures were used, and X-ray diffraction and DSC showed that amylose-sodium stearate inclusion complexes were formed and did not dissociate during foam formation. In the absence of PVOH, water absorption and foam shrinkage at 95 % RH were decreased due to the hydrophobicity of the complex. When PVOH was added to the formulation, increases in both the expansion ratio and the shrinkage of the foam were observed due to an increase in foam flexibility. However, shrinkage at 95% RH was still less than that observed with un-complexed amylose.