Melt Flow Rate of a polymer is simply a measure of the rate of flow of the polymer, when melted. It can be evaluated with the help of a Melt Flow index Tester.
The result obtained through a melt flow test is called the melt mass-flow rate (MFR) or melt volume-flow rate (MVR). In simple terms Melt Flow Rate can be defined as the amount of mass or volume of a polymer that flows through a small aperture at a specified temperature and pressure.
The Melt Flow Rate test is a simple test wherein a small amount of a thermoplastic sample (usually in granule or flake form) is heated in a barrel at a specified temperature. The melted, viscous fluid is then, forced out of a capillary die, and with the help of a piston loaded with dead weights. Once enough sample extrude has exited the die, it is removed and weighed, or the volume of the sample is measured by the machine.