AbstractThis paper explores the concept of continuously extruding reacting polyurethane foams. The control of the process is hampered by the fact that the state of the conversion of the extrudate is not directly observable. We present the general concept, describe an experimental apparatus, present a mathematical model of the process, and report on some initial experimentation. In the experimental work, low density (0.5 g/cc) polyurethane foam was extruded in a cylindrical cross section at a rate of 250 g/min. Maximum run time was thirty minutes. In all cases, the experiment had to be stopped due to problems in the process. Problems requiring further investigation were identified: channelling of uncured liquid foam around the solid cured foam, poor skin quality due to adhesion of the foam to the wall, and the general lack of observability of the conversion field.