A Capillary Rheometer as well as a Melt Flow Indexer can compare the flow behaviour of polymer plastics. However, there are significant differences in setup, measurement process and application.
The diagram shows a comparison of melt index measurement and capillary rheometer on two materials with different surface roughness in the extrudate. In the range of MFR measurements is a difference of 5% between the materials.
The measurement with the capillary rheometer is carried out over a wide shear rate range. Thus, the flow characteristic or the viscosity of plastics, in the shear rate range of processing can be determined.
The data are approximated by the flow law after Carreau-Winter. Here, the zero viscosity, one of the most important model coefficients, show a very clear deviation of 20%. The melt flow index measurement can detect a difference between the materials at low shear rates. In order to determine the flowability of plastics in the processing window higher forces or shear rates are needed. A capillary rheometer can carry out the characterize of the flow properties of plastics in the shear rate window of processing.
In addition to the viscosity measurement of materials, the GOETTFERT Capillary Rheometer also offers the option of generating additional material-specific data through add-ons.