The principle is based on the direct measurement of the melt pressure drop in the die head. Unlike with piston type capillary rheometers, the melt is transported continuously by the extruder screw and, possibly, a melt pump to the capillary die head. The apparent – and later on true viscosity can be calculated by measuring the wall shear stress due to the pressure drop in a given geometry and the shear rate by measuring the volume flow and providing the specific melt gravity of the material. The software enables the customer to apply industry standard correction factors (i.e. Rabinowitch) to calculate the true viscosity. The software also provides several approximation models how to interpret the measured viscosity (Power law, Carreau).

For the round capillary viscosity test, the software can be used to even out the pressure loss due to the running-in of each capillary insert according to Bagley.

Shear rate:
2 x 10¹ -1 x 10³ s^-1

capillary dimensions:
(diameter x length)
20 x 0,8 x 160 mm

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Shear rate:
4 x 10⁰ -1 x 10² s^-1

capillary dimensions:
(diameter x length)
20 x 2,0 x 160 mm