Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 18, 2013
Publication Date: April 18, 2003
Citation: Lawton Jr, J.W., Selling, G.W., Willett, J.L. 2003. PHYSICAL PROPERTIES OF EXTRUDED AND INJECTION MOLDED CORN GLUTEN MEAL. Industrial Crops and Products. xx. Interpretive Summary: Corn gluten meal (CGM) a co-product of the corn wet milling and bio-ethanol industries was shown to be processable into injection moldable resin on traditional industrial plastic processing equipment. CGM was mixed with decanoic acid and extruded through a twin screw extruder and then injection molded into dumbbell shaped test bars. The bars had lower than expected strength when stored at 50% relative humidity. Magnified pictures of the bars revealed that they were not fully melted. Changes were made in the manufacture of the bars which resulted in test bars with greater strength. Water exposure affected the properties of the CGM composites. CGM bars that were stored at lower relative humidities had greater strength than did CGM bars stored at higher relative humidities. Soaking the bars in water also decreased their strength and increased their elongation. However, if the bars were only soaked for an hour, their physical properties were fully recoverable after drying. The application of this knowledge will aid in the utilization of CGM, an important co-product of the bio-ethanol industry and improve the economics of this industry.
Technical Abstract: This study was performed to investigate the compounding of corn gluten meal (CGM) and decanoic acid and to evaluate their mechanical properties. The mixture of CGM and 30% decanoic acid was compounded in a twin screw extruder, followed by injection molding. Scanning electron microscopy (SEM), tensile testing, ageing and water emersion were carried out to assess the composites. Tensile strengths of the composites were 13.2, 11.1, and 7.8 MPa when conditioned at 20, 50, and 70% RH, respectively. SEM of the composites revealed a lack of complete CGM melt during processing. Increasing the feed rate during extrusion did seem to provide a better melt, but only slightly increased the tensile strength of the composites to 14.9, 13.6, and 8 MPa when conditioned at 20, 50, and 70% RH, respectively. The composites were in their glassy state despite containing 30% decanoic acid even when conditioned at 70% RH. The composites also became brittle after ageing, which is a characteristic of physical ageing of glass. The composite's tensile strength decreased and their elongation increase after soaking in water, as would be expected. After soaking the composites for an hour and re-conditioning for seven days at 50% RH, their tensile properties returned to their original values. Longer soaking times resulted in greater loss in tensile strengths, resulting in 3 MPa for 24 hour soaking and 0.8 MPa for 120 hour soaking. It is believed that the loss in tensile strength is due entirely to the water absorption and not to any physical deterioration of the sample. Tensile bars that were soaked for 120 hours had elongation of almost 250%.