Evaluation of cup-type jig for parallel plate rheometer by viscoelastic flow simulation

Abstract

In order to measure the flow characteristics of polymer melt with high melt index, e.g. polyester and polyethylene terephtalate (PET) used for fiber processing, we discuss the utility of the cup-type jig for measurement of the steady-state shear flow characteristics in the rotational-type rheometer, especially parallel plate rheometer, by using the viscoelastic flow simulation. The multiple mode Phan-Thien Tanner (PTT) model was employed as the constitutive equation. We considered the deviation between the rheological data from the parallel plate rheometer with cup-type jig and the data from the normal parallel plate rheometer with the same disk diameter. As a result, the deviation of shear viscosity increased with the distance between the disk and the cup-type jig. The average value of the deviation of shear viscosity increased linearly with this distance. Then, the absolute value of the deviation of the first normal stress difference also seems to increase with this distance. On the other hand, the deviations of shear viscosity and the first normal stress difference are almost independent of the cup-type radius in the region over about 1.2 times of jig diameter divided by the disk radius. These results imply that large radius of cup-type jig and narrow distance between the disk and the cup-type jig would be suitable for measurement of polymer melt flow characteristics using the parallel plate rheometer with the cup-type jig. In addition, these obtained results would imply that to use the cup-type jig is valid for measurement of rheological data.