Measurement Techniques and Methods for the Pressure Coefficient of Viscosity of Polymer Melts

Viscosity is a prominent rheological property of polymer, which is affected by temperature, pressure, shear rate, molecular structure, and other factors. Despite the importance of the pressure effect, there remains a paucity of investigations on the dependence of pressure on viscosity compared with other factors, such as shear rate and temperature. Previous research has established that the correlation between pressure and viscosity is usually expressed by the pressure coefficient. In this paper, different measurement techniques and methods for the pressure coefficient of viscosity of polymer melts are reviewed and evaluated on the basis of published experimental data. The capillary rheometer with a pressurized exit chamber is widely employed because of its accuracy and simple use. Besides, the accuracy and relationship of pressure coefficients determined by different methods are discussed.