MFR is an ISO standard measure which describes how easily a given melt flows. The higher the value the more readily it flows.
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.