Plastics are materials which show important volume variations when they undergo temperature changes. During the injection molding process, polymer parts may shrink and so become unstuck from the mold walls. It drives then to the apparition of air gaps which may modify both the shape of the part and its cooling time. The cooling of such a polymer part is studied, taking into account key parameters such as thermal contact resistances, residual stresses, or PvT diagram. The results of the numerical simulation, using a coupled thermomechanical approach, are compared to experiments that are led in parallel. (C) 2003 Elsevier Ltd. All rights reserved.