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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.

Polypropylene is commonly used as a binder for ceramic injection molding, and rapid cooling is often encountered during processing. However, the crystallization behavior of polypropylene shows a strong dependence on cooling rate due to its semi-crystalline characteristics. Therefore, the influence of cooling rate on the quality of final product cannot be ignored. In this study, the fast differential scanning calorimetry (FSC) test was performed to study the influence of cooling rate on the non-isothermal crystallization behavior and non-isothermal crystallization kinetics of a copolymer polypropylene (PP BC03B). The results show that the crystallization temperatures and crystallinity decrease as the cooling rate increases. In addition, two exothermic peaks occur when cooling rate ranges from 30 to 300 K·s-1, indicating the formation of another crystal phase. Avrami, Ozawa and Mo equations were used to explore the non-isothermal crystallization kinetics, and it can be concluded that the Mo method is suitable for this study. [ABSTRACT FROM AUTHOR]