During the cooling of an injected polymer, a very strong coupling exists between the thermal and mechanical phenomena. In order to fill in the mold and to compensate the effects of reduction of the thermal shrinkage, the pressure in the molding cavity is maintained to a very high level. The purpose of this paper is to show the essential importance of thermomechanical coupling present during the cooling of a hot polymer in a cold mold via a comparison between experiments and numerical simulation. Experiments show that the polymer-mold contact evolves under the effect of the internal contraction caused by the lowering of temperature. On the one hand, the air gap width, depending on the shape of the part, modifies the Thermal Contact Resistance (TCR) between the mold and the part. On the other hand, shrinkage is divided between the two sides of the part depending on the internal stresses, so that the geometry of the part is also linked to changing temperature. The resolution of the coupled thermal and mechanical problems allows us to predict the shape of the part, the stresses, the temperature field in the polymer and in the surrounding mold, and the air gap widths on both sides.

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