Converging flow inline rheometry for engineering extensional viscosity of uPVC

An inline rheometer is described for determination of an engineering extensional viscosity using pressure drops in conical converging flow under fixed extruder processing conditions. A 'temperature cross' with 16 thermocouples is incorporated for detailed measurement of the temperature of melt passing to the rheometer. Temperature variations are taken into account in extracting extensional viscosity values using a modified version of the analysis by Binding. Results are reported for a profile grade uPVC. The applicability of the Binding analysis in this case is examined and confirmed. Results compare well with published data for profile grade uPVC, taking into account differences in formulation.