Thermal Properties and Cellular Structure of Cornstarch-Based Foams Formed by Extrusion Technology

Abstract

The aim of this work was to investigate the edible corn grit/PVOH (polyvinyl alcohol) blends of their thermal properties by using differential scanning calorimetry (DSC) and thermogravimetric analysis, and the average pore sizes and cellular structures of the blend foams were also characterized by using scanning electron microscopy. The thermal decomposition of edible corn grit/PVOH blends shifted slightly toward lower temperature compared to PVOH. This result shows that edible corn grit/PVOH blends suppress the thermal stability of PVOH. DSC result shows that PVOH and edible corn grits were miscible. Furthermore, the cell sizes become smaller and more uniform and the cell walls become thinner with the increase in PVOH ratio. Moreover, using the CaCO3 also made the cell sizes become smaller and more uniform. Corn-based foams have practical mechanical properties, but they are difficult to mold into shaped products. They will have a greater commercial potential if the extrusion process were more amenable to making molded foam articles, such as food and beverage containers, and if it were compatible with fiber or other reinforcing materials. Practical Applications In this study, edible corn grit/PVOH blends were prepared by using extrusion technology and the CaCO3 as the thermal conductor. Corn grit is renewable from carbon dioxide, water and sunshine. It is biodegradable, cheap and easily modified physically or chemically. This means someday it is unnecessary to rely on petroleum to prepare polymers; people may “plant” polymers of suitable performances from the earth, and the environmental problems will no longer be as severe as today. At present and in the near future, different physical and chemical approaches are effective strategies to develop completely starch-based biodegradable polymers of appropriate biocompatibility, degradation rate and physical properties for various applications.