AbstractIt is known that oxidation occurring during processing of some polymers like PVC and polypropylene causes their deterioration. This, in turn, detracts from its service life. This study shows how the extrusion process shear can be detected and followed stepwise and in effect be controlled. Separate identification of fragmentation and crosslinking levels are determined. Quantification of shearing, fragmentation, and crosslinking of the PVC melt is used to derive service life loss due to extrusion processing.