On-line, in-line and off-line rheometry of polyethylenes

In-process rheometry (on-line & in-line) carried out during twin screw extrusion of several polyethylenes (LDPE, LLDPE and three HDPEs) is compared with conventional off-line rheometry for both shear and extensional properties. Use of two on-line and two off-line rheometers allowed comparison of data from a range of commercial instruments in order to validate their performances. In-process shear flow rheometry was undertaken using a six-sensor in-line extrusion die rheometer on a twin screw extruder. Results from the five rheometers were compared and good agreement observed between the different routes to measurement, for these relatively stable materials.