Comparison of in line, on line and off line rheometry of polyethylene melts

In-process rheometry is compared with conventional off-line rheometry for both shear and extensional properties of an LDPE (with 0 and 50wt% Mg(OH)(2) filler) and an LLDPE. In-process rheometry was undertaken using a six-sensor in-line rheometer (ILR) on a Betol 40mm twin screw extruder, and a Rosand On-Line Rheometer (OLR) which employs an indexing capillary die system. Both devices allowed measurement of shear behaviour, the OLR also providing die entry pressure loss measurements. The results were compared with those from a twin bore capillary rheometer. Good agreement has been observed between the three routes to measurement, for these relatively stable materials.