Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2009
Publication Date: August 5, 2009
Citation: Selling, G.W., Woods, K.K., Biswas, A., Willett, J.L. 2009. Reactive Extrusion of Zein with Glyoxal. Journal of Applied Polymer Science. 113(3):1828-1835. Interpretive Summary: Developing new processes to produce articles that are resistant to changes on exposure to various liquids will help the penetration of zein, a potentially significant co-product of the bio-ethanol industry, in traditional petroleum based markets. The research presented here describes the use of a crosslinking reagent, glyoxal, to improve the tensile strength and solvent resistance of zein using reactive extrusion techniques. By using an extruder as the vessel for carrying out the reaction on a continuous basis, significant savings, due to elimination of solvent, can be realized. The articles that are produced from the extruded zein can be obtained using either compression or injection molding. Due to cost reasons, injection molding is the preferred technique for making most typical plastic parts. When using 2% or less glyoxal, injection molding was successfully performed. At higher levels of glyoxal, under the conditions employed, injection molding was unsuccessful as the bars produced were misshapen. For these samples having higher levels of glyoxal, compression molded samples could be obtained. At levels of 1.75% glyoxal or higher, the articles would not dissolve in typical solvents that would dissolve zein. Results from this work will be helpful in developing new zein products, therefore improving the economics of the bio-ethanol industry.
Technical Abstract: Cross-linked zein has been produced using glyoxal as the cross-linking reagent via reactive extrusion for the first time in a twin screw extruder using dilute sodium hydroxide as catalyst. Tri(ethylene glycol) was used as a plasticizer for various items. The extrudate was then ground and processed using either compression or injection molding. At the highest level of glyoxal (6%), tri(ethylene glycol) was used at 10% as a plasticizer to allow further processing to take place. With this formulation, samples could be obtained from the injection mold, however, the samples were misshapen due to spontaneous relaxation after the mold was opened. When lower levels of glyoxal were used, injection molded sample bars of similar quality to control were obtained. The physical properties of these samples were similar to control. At glyoxal levels of 1.75% and higher the samples were resistant to dissolution by acetic acid.