Of all the tests used by the plastics industry, melt flow rate testing (or melt flow index) is the most widely used. It is traditionally associated with testing polyethylene materials to determine the lot-to-lot consistency of resin lots or batches for quality control purposes. It is, however, also used for other purposes such as testing new materials, determination of material stability versus residence time within plastics processing equipment, or the assessment of regrind content within materials or moldings. It is generally a low shear rate test; however, larger weights can increase the shear rate.
A flow rate test measures a polymer’s mass flow rate (grams extruded in 10 minutes) using an orifice under specified conditions of temperature and load. Machines that determine flow rate are generally called Melt Indexers or Extrusion Plastometers. Test methods by ISO, DIN, ASTM, and others specify heat chamber and piston tip diameter such that the shear stress on the polymer is the same in all machines for a given load. In addition, material specification guidelines (by ISO, DIN, ASTM, GM, etc.) may exist, providing further constraints on how a particular material processes.
Specifically designed for the thermoplastics resin industry, the Dynisco LMI5500 Series Melt Flow Indexer has an array of features and benefits that range from ground-breaking accuracy to a unified software platform between all laboratory and online production equipment.
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