Modification of Rheological Properties of Branched Polyethylenes by a Thermomechanical Treatment

摘要

Shear refinement has been studied in four LDPE, which have been molecularly and rheologically characterized. They have been subjected to a pre-shearing in a cone-and-plate rheometer, and the decrease of viscosity, associated with the disentanglement of macromolecules, has been analyzed as a function of different mechanical parameters: shear rate, strain, stress, specific energy. It appears that disentanglement mechanisms are complex and cannot be explained by a unique molecular parameter, e.g., the molar mass between entanglements.