Starch Foam Expansion in a Closed Mold

Processes with thermal treatment of starch-based materials for biologically degradable packaging products are analyzed here. The paper describes experiments on thermal forming of potato starch-based water suspensions in a closed mold at elevated pressures and temperatures of walls heated up to 200 °C. The time course of temperatures and also the sample expansion were detected by a network of thermocouples and compared with the pressure recorded inside the mold. Evolution of temperature profiles enables the estimation of time courses of sample expansion. Experiments with marking particles show that the crust sticks to the heater walls and only the sample core expands. Temperatures and pressures are closely related during expansion and the free water evaporation stage. Experiments confirm that temperatures are more or less uniform in the longitudinal direction and that the time profiles of temperature and pressure are characterized by peaks corresponding to perforation and recovery of foamed structure.