Study of shear nucleation theory in continuous microcellular foam extrusion

During microcellular foaming, the classical nucleation theory has always been considered as the basis of investigation. But from experiments in continuous foam extrusion, we find that the classical theory has its limitations in predicting the cell structure from experimental conditions due to its original development from the static thermodynamic equilibrium process. The importance of shear effects upon bubble nucleation has been much investigated in recent years, but no systematic analysis was developed to interpret its nucleation enhancement mechanism. In the present paper, the shear effects are interpreted from the point of view of shear energy, and the theoretical analysis coincide well with the experimental results. (C) 2003 Elsevier Science Ltd. All rights reserved.