Abstract:The rheological behavior of high molecular weight polyethylene terephthalate (PET) melt under a pressure field was studied by capillary rheometry and reverse pressure chamber conditioning. The results show that with an increase in shear rate, the shear viscosity of high molecular weight PET decreases gradually, showing obvious "shear thinning" behavior, which is typical of pseudoplastic fluids. The shear viscosity of high molecular weight PET is increased exponentially with an increase in melt pressure, and the variation conforms well to the Barus equation. The shear viscosity of high molecular weight PET is decreased with the increase of temperature. The conversion factor of high molecular weight PET is 3.4, and the contribution of the pressure increase to shear viscosity is equivalent to that of the temperature decrease. High molecular weight PET is a non-Newtonian fluid, with an increase in temperature, the non-Newtonian index of high molecular weight PET is increased gradually, and the fluidity of the high molecular weight PET gradually approaches Newtonian fluid characteristics. The shear viscosity-temperature dependence of high molecular weight PET is increased with increasing pressure and the temperature sensitivity of the shear viscosity of high molecular weight PET is decreased with an increase in shear rate. With an increase of shear rate and temperature, the dependence of shear viscosity on the pressure of high molecular weight PET melt is decreased gradually.