A new approach and a technique has been proposed and developed to measure the melt flow index (MFI) using a Helical Barrel Rheometer (HBR), the portable on-line viscosity measuring instrument. The HBR can be fed online from a melt slip stream, or off-line with pellets. The viscosity is calculated from the pressure measurement and rotor speed, without measurement of the torque or the flow rate. The measured viscosities are representative of flows within the processing equipment, from which not only an MFI value can be calculated and monitored but also a spectrum of viscosity data over a wide range of shear rates can be obtained in a semi-continuous manner.
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