Foaming of polyurethane (PU) films using supercritical CO2 as a blowing agent, a "green" and high-efficient approach, has been studied. Microcellular foam material was prepared by saturating the polymer with CO2 and its morphology was characterized by scanning election microscopy (SEM). The influence of processing parameters, such as pressure, temperature and soaking time, on the foam morphology was investigated. It was found that the size and distribution of the micro-cell could be controlled conveniently by changing the processing conditions. The results of dynamic mechanical temperature analysis (DMTA) showed that the damping property of the foamed materials was greatly improved and had a maximum value, tan delta = 3.88 at 63 Hz due to the properties of the storage and loss moduli compared with the original PU. Reduction of the mass density led to a decline in the mechanical properties of the foamed materials. (C) 2004 Elsevier B.V. All rights reserved.