Thermal Properties of Starch-Based Biodegradable Foams Produced Using Supercritical Fluid Extrusion (SCFX)

Starch-based extruded foams are in demand for many industrial applications because starch is biodegradable, inexpensive, and readily available in abundant quantity. In this study, the production of starch-based extruded foams using supercritical fluid extrusion (SCFX) having thermal properties such as heat capacity, thermal conductivity and thermal diffusivity comparable to commercial products have been reported. Pregelatinized corn starch was extruded with different concentrations of whey protein isolate (WPI) (0, 12, and 18 wt. %) with supercritical CO2 (SC-CO2) injection rates of 0.0, 0.4, 0.8, and 1.2 wt%. It was possible to vary the expansion and the density of SCFX extrudates by manipulating WPI concentration and SC-CO2 injection rate. It was observed that the heat capacity, thermal conductivity and thermal diffusivity of starch-based SCFX extrudates were strong functions of their void fraction. The SCFX system is a useful tool for production of starch-based biodegradable foams, which do not require any organic solvents and are environmentally friendly and sustainable.