Determination of the pressure dependence of polymer melt viscosity using a combination of oscillatory and capillary rheometer

摘要

For an accurate simulation of a high-pressure injection molding process by using the CAE software, it is important to understand the pressure sensitivity of a polymer's melt viscosity. The current work describes a method for the determination of the pressure dependence parameter D-3 of the Cross-WLF model. It uses a combined rheological technique using both dynamic and capillary rheometers. Three grades of polycarbonate homopolymers were studied in this work and their complex viscosities were measured using a dynamic shear rheometer. The dynamic data were used to obtain six out of the seven parameters of the Cross-WLF, except D-3. A capillary rheometer fitted with a counter pressure chamber was further used to characterize the pressure dependence of the zero shear viscosity and to determine the D-3 parameter. Finally, the derived parameters were validated by carrying out injection molding with a box tool and comparing the actual pressure profiles with simulation results using the Autodesk (R) MoldFlow (R) software. The validation results indicated that actual pressure profiles from the simulation were found to be less than 10% than that of injection molding. POLYM. ENG. SCI., 2019. (c) 2019 Society of Plastics Engineers