Microcellular starch-based foams

Interest has been growing in the development of a new class of foams called microcellular foams. These foams have extremely small cells (<10 mu m) and possess unique and useful properties. This chapter discusses some of the important methods for making macro- and microcellular polymeric foams and discusses their structural, physical and mechanical properties. Particular emphasis is focused on starch-based foams. Starch can be extrusion processed into foams having relatively large cells. Microcellular starch-based foams can be made using methods originally developed for other polymeric materials. These foams are white, opaque, have densities ranging from 0.10 g/cm(3) to 0.32 g/cm(3), compressive strengths of 0.22 MPa to 0.97 MPa, and moduli of elasticity from 5.1 MPa to 33 MPa. The microcellular starch-based foams have low thermal conductivity (0.024 W/mK to 0.036 W/mK), large pore volume (0.17 to 0.63 cm(3)/g) and large total surface areas (50 to 145 m(2)/g).