The Factors Affecting the Shear Viscosity of Poly (Ethylene Terephthalate) Melt Under Reverse Pressure

In this study, the variation in the rheological behavior of poly (ethylene terephthalate) (PET) melt was investigated by the capillary rheometer and counter pressure chamber where the pressure at the outlet of the capillary was higher than the normal pressure. The investigation revealed that the shear viscosity of PET decreased with increasing temperature. Noticeably, the effect of temperature on the shear viscosity displayed variation under all the conditions of shear rates and pressures, and this effect was more significant at 50 MPa or at 216 s−1. The viscous fluid activation energy of PET was measured to be 42.97–79.22 KJ·mol−1, which increased with an increase in pressure and decrease in shear rate.