Melt flow rate. Melt mass flow rate or melt flow rate (MFR) gives an indication of melt processing properties of a polymer. Shear rate range is, however, narrow and much lower than in the most of processing applications. It gives thus very limited information about melt flow behaviour. The method is a kind of capillary measurement. The equipment consists of a barrel, a piston with a place for loading masses and a die. The sample is charged into the barrel and heated up to a specified temperature. After that the piston is loaded extruding the polymer through the die. Melt flow rate (MFR) is defined as a mass flown through the die in 10 min. The weights mostly used with polyolefins are 2.16 kg, 5 kg, 10 kg and 21.6 kg. In addition to the evaluation of flow properties MFR serves as a rough estimation of molecular weight. Usually also Flow Rate Ratio (FRR) is determined. This ia defined as a ratio of two MFR values obtained with two different weights. FRR can be used as a rough estimation of molecular weight distribution.