Viscosity Measurement by using Melt flow Index for Thermoplastic polymers

Abstract

In plastics manufacturing, the melt flow index (MFI) is used as a routine indicator of rheological behavior when more expensive and laborious determinations of well-defined material functions are impractical. The MFI is the mass flow rate in a pressure driven flow through a standardized abrupt cylindrical contraction into a short tube performed under a standardized combination of pressure drop and temperature. In this research, we used Polyethylene low density grade of extrusion and poly propylene grade of injection to explore the connections between rheological properties and melt index. We explore the role of shear by modeling the flow through the melt indexer using the different applied loads from 1.2 to 5 kg at different temperature to the same material to give us different value of MFI, and then calculate the mass flow rate, volume flow rate, pressure difference, viscosity, maximum shear stress and maximum shear rate. It was found that the viscosity is affected by temperature, changing the temperature change of the value of viscosity, and this change is inversely. We present our results in different charts designed to help plastics engineers specify the MFI of a plastic for an industrial manufacturing process of known material functions.