Comparison of Measurement Techniques for Evaluating the Pressure Dependence of the Viscosity

Applied Rheology

Ernst Benoît¹  Moldenaers Paula²  Goubert Alain²  Vermant Jan²  Göttfert Axel³ 

[1] CERDATO, Elf Atochem F-27140Serquigny, France;Department of Chemical Engineering, K.U. Leuven, de Croylaan 46, B-3001Leuven, Belgium;Göttfert Werkstoff-Prüfmaschinen GmbH, D-74711Buchen, Germany;

关键词: rheometry;    pressure dependency;    polymer melts;   

DOI  :  10.1515/arh-2001-0003

来源: DOAJ

【 摘 要 】

The different methods that can be used for measuring the effect of a hydrostatic pressure on the viscosity of polymer melts are evaluated. A linear low-density polyethylene is chosen as test material, as it can be expected to have a small pressure dependency. Special attention is given to methods employing capillary rheometry, as these methods yield a range of shear rates and pressures that are typically encountered under polymer processing conditions. The accuracy of the different techniques is evaluated considering also the complexity of the experimental devices. First it is investigated to which extent standard capillary rheometry can be used to extract information about the pressure dependency of the viscosity. Secondly, it is shown how the accuracy can be greatly increased by the simple addition of a pressure chamber below the exit of the capillary, with a needle valve to regulate the back pressure. The results from this device are compared with those from a more robust method using a pressurized double piston rheometer and with literature data. The experimental values for the pressure coefficient of the viscosity will also be compared with those predicted from PVT data using Utracki's method.

【 授权许可】

Unknown