MFR is an ISO standard measure which describes how easily a given melt flows. The higher the value the more readily it flows.
MFR is identical to the ASTM standard, melt flow index (MFI).
To measure the MFR, the material is first heated in a barrel at a known temperature. A known weight is then applied to the top of the piston to drive the melt through a capillary die at the end of the barrel. MFR is the mass of the material that passes through the die in a given time interval under the specific conditions of temperature and pressure.