Controlled Degradation of Poly(propylene) in Industrial Extruders

Abstract

The main objective of this work was to study the controlled degradation of PP in industrial extruders at different operating conditions. Firstly, the investigation of certain key polymer properties, such as the MI and the MWD, revealed that the changes undergone by the polymer resin during the reactive extrusion depend strongly on the operating conditions. In the absence of oxygen, the results indicated that spontaneous thermal and/or mechanical degradation were not very important. Therefore, resin properties were not expected to change during extrusion if no peroxide was fed into the extruder, in the absence of oxygen. On the other hand, in the presence of oxygen, MWD analysis showed that the MWD could be shifted towards higher or lower molecular weights, indicating that both chain growth and chain scission were possible during extrusion. Finally, simple expressions are presented here in order to allow for the monitoring and control of the important final properties of the extruded resin.