The melt flow index (MFI) is a basic analyses to get a sense of the flow behavior of thermoplastic polymers. The MFI value is a widely used parameter for selecting polymer grades for a certain application. In principle this method is quite simple, The polymer is loaded into the barrel and is heated in order to bring the thermoplastic in a molten state at a constant temperature. A piston exerts a constant gravimetric pressure of usually 2.16 kg or 5.00 kg. The amount of polymer that flows out of a capillary of fixed dimensions is given in grams per 10 minutes. A high MFI corresponds with a low viscosity (easy flow) and vice versa. Other rheological properties such as elasticity, tan delta and viscosity can be determined via more complex devices like the RDS. We have many devices at our disposal capable of acquiring rheological data.

When this method is combined with a melt volume rate (MVR) the density of the polmer melt can be determined. A MVR is reported in mL/10min.

It is possible to perform seperate MFI and MVR measurements at a maximum temperature of 350°C.