Peroxide-controlled degradation of poly(propylene): Rheological behaviour and process modelling

The control of the molecular weight distribution of poly(propylene) resins by peroxide degradation is widely used in polymer industry. It allows to ad just the viscosity of these resins to the level required for processing app lications. The purpose of this work was to characterise the influence of pe roxide degradation on the rheological behaviour of an homopolymer PP and a block copolymer PP/PE, and to use these results to obtain a predictive mode l of the degradation in a twin-screw extruder. By coupling a thermomechanic al model of the twin-screw extrusion process, a kinetic model of the consid ered reactions and the rheological behaviour, it was possible to calculate the changes in molecular weight along the extruder, during the peroxide-con trolled degradation.