Enhancing High-Pressure Capillary Rheometer Viscosity Data Calculation with the Propagation of Uncertainties for...

Area of Science:

• Polymer Science
• Rheology
• Measurement Science

Background:

• High-pressure capillary rheometry is standard for measuring polymer melt shear viscosity.
• Viscosity calculations involve Bagley and Weissenberg-Rabinowitsch corrections, susceptible to measurement inaccuracies.
• Existing methods lack robust quantification of uncertainty in derived viscosity values.

Purpose of the Study:

• To propose and demonstrate a method for quantifying uncertainties in shear viscosity measurements of polymer melts.
• To evaluate the impact of incorporating viscosity uncertainties into viscosity model parameter estimation.
• To compare the performance of weighted versus standard residual sum of squares minimization.

Main Methods:

• Propagation of uncertainties calculation applied to capillary rheometry data.
• Experimental validation using a polycarbonate melt.
• Parameter estimation of the Cross-WLF viscosity model using weighted and standard residual sum of squares.
• Numerical simulations of rheometer measurements for validation.

Main Results:

• Quantified viscosity uncertainties were successfully derived for a polycarbonate melt.
• Weighted residual sum of squares fitting, incorporating uncertainties, improved model accuracy by ~16% at lower shear rates.
• Derived viscosity uncertainties led to more precise Cross-WLF model coefficients.
• Both fitting methods showed deviations at high shear rates, likely due to non-isothermal conditions.

Conclusions:

• Quantifying measurement uncertainties is crucial for accurate viscosity determination in polymer melts.
• Incorporating viscosity uncertainties into model fitting enhances parameter precision and predictive capability.
• Further research is needed to address deviations at high shear rates, potentially involving non-isothermal flow modeling.