Capillary Rheometer End Correction Data Processing Workflows
End-corrected capillary rheology isolates entry losses and non-Newtonian wall shear rates to establish accurate melt viscosity curves for compounding quality control.
Mooney Slip Correction
Meaning
Mathematical adjustments in rheological measurements account for the wall slip that occurs when testing highly filled polymers or elastomers in a viscometer. Applying the Mooney slip correction allows engineers to calculate the true shear rate and viscosity of the material by subtracting the velocity of the slip at the wall from the total flow rate. This correction prevents the underestimation of viscosity during process design and extrusion modeling.
It relies on measuring flow curves using multiple capillary dies or rotor sizes with different surface-to-volume ratios.
Rheological Accuracy
Process simulation depends on accurate viscosity data to predict pressure drops in dies and molds. Using the Mooney slip correction ensures that the experimental data reflects the true flow behavior of the polymer melt. Without this correction, the apparent viscosity would be artificially low, leading to incorrect extruder sizing.
Experimental Procedure
Flow curve measurement must be executed systematically at various shear rates and temperatures. The Mooney slip correction requires tests to be performed using at least three different die diameters or gap sizes to isolate the slip velocity. Comparing these runs reveals the relationship between wall shear stress and slip velocity.
Industrial Consequence
Extrusion dies can fail to produce correct profiles if the material slips unpredictably. Incorporating the Mooney slip correction into the design phase allows toolmakers to adjust die geometry to account for slip. This adjustment prevents expensive rework of steel dies after production starts.