Submitted to: Cereal Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/18/2007
Publication Date: 3/20/2008
Citation: Lawton Jr, J.W., Selling, G.W., Willett, J.L. 2008. CORN GLUTEN MEAL AS A THERMOPLASTIC RESIN: EFFECT OF PLASTICIZERS AND WATER CONTENT. Cereal Chemistry. 85(2):102-108. Interpretive Summary: Corn gluten meal (CGM) is a co-product of the corn wet milling and bio-ethanol industries. Corn proteins are now accumulating because of the increased production of fuel ethanol from corn. Zein, a protein, is extracted from CGM. Due to its extraction cost, zein is too expensive to be used as a thermoplastic. This research was done to examine if CGM could be processed as a thermoplastic, thereby utilizing zein's thermoplastic nature without the expense of extraction. It was found that CGM could be processed into a thermoplastic resin by mixing it with plasticizers (triethylene glycol and octanoic acid). There was an optimal water content for the CGM depending on the plasticizers used to produce thermoplastic CGM. CGM that was mixed with plasticizers at its optimum water content produced stronger materials than samples that were not mixed at the optimum water content. Like all bio-materials, CGM composites were affected by relative humidity (rh). CGM composites that were stored at low rh were stronger but more brittle than samples stored at higher rh. These samples were weaker but more flexible. The economics of fuel ethanol will be more advantageous by finding new uses for CGM, one of its co-products.
Technical Abstract: Corn gluten meal (CGM) was studied to investigate the effect plasticizers and water have on its melt processing, and how this melting affects its mechanical properties. CGM containing varying amounts of water were mixed with 30%(w/w) plasticizers; (glycerol, triethylene glycol (TEG), dibutyl tartrate, and octanoic acid in a Haake bowl mixer at 80 deg C. The amount of water in the CGM affected the amount of torque produced in the Haake mixer. This increase seen in torque was correlated with how well the CGM melted in the mixer, SEM's of CGM melted in the mixer showed a more uniform homogenous structure when processed at its optimum moisture content. Glycerol, TEG, and dibutyl tartrate produced the greatest torque when the CGM contained less than 1% water. Octanoic acid produced the greatest torque when the CGM was processed at 8% moisture. CGM plasticized with TEG and octanoic acid was mixed at either its optimum moisture or at 9.6% moisture and then compression molded into tensile bars. The tensile strength of the bars that were mixed at their optimum moisture content was significantly greater than the bars mixed at 9.6% moisture. The tensile properties of the CGM samples were affected by relative humidity (rh). The tensile strength decreased and its elongation increased as rh increased. CGM plasticized with TEG saw a greater change in its tensile properties due to rh than did octanoic acid plasticized CGM.