Effects of Operating Conditions on the Cellular Structure and the Thermal Properties of Extruded Foams Made From Corn

Abstract

The characteristics of a corn extrudate generally appear similar to commercial plastic foam cushioning materials. If extruded foams from whole yellow dent corn are used for loose fill cushioning material, low cost will be realized. In addition, this extruded foam is biodegradable and might even be recoverable as animal feed or as an ethanol feedstock. It could also be spread on farm fields as a soil amendment. Extrusion technology has been applied in cornstarch processing for many years. Different categories of extruders have been developed to give various advantages and disadvantages as used for production. The low-moisture (low-cost) extruder cooker is a good choice for producing low cost expanded corn for packaging use. The objective of this study is to focus on the feed compositions and screw configurations affecting the cellular structure and the specific heat of extruded foams and to evaluate corn/ PVA extrudates as packaging material. Experimental results indicated that: 1. The size of air cells became smaller and more uniform, and the air cell wall became thinner with the increase in screw pitch and screw speed. Moreover, using the food grade corn grits also made the size of cells smaller and more uniform. 2. Treatments 5 and 22 had the highest specific heats. For all treatments, the specific heat increased linearly as the temperature increased. 3. The extrudates from Treatments 5 and 22 have potential applications as thermal insulation applications for their high specific heat values.