Melt Flow Index or Melt Volume Rate is the measure of the ease of the flow of the melt flow of the thermoplastic polymers. It is the weight of the polymers in grams that flows in ten minutes through a capillary tube of specific length and diameter when a specific amount of pressure is applied with the help of different weights at different temperatures. This process usually helps to correlate the value of melt flow index with the grade of the polymers which the user have to choose for different applications to produce various types of products. The test results of melt flow index measurement are expressed in grams per ten minutes rather than any other unit. The measurement of melt flow rate of plastics is also defined clearly in various standards like ISO 1133, ASTM D1238 and many more.
Measuring the melt volume rate of the plastic is the indirect method of measurement to determine the molecular weight of the plastic granules at a high melting point corresponding to low molecular weight. Same time, the melt flow rate is the best measurement procedure which helps to determine the ability of the plastic resins to melt under a determined pressure. This rate is inversely proportional to the viscosity of the plastic in the molten state which is determined on the basis of the pressure which applied to the resins. The ratio between the two values of the MFR i.e. Melt Flow Rate of a material at two different weights is used to measure the molecular weight distribution of the plastics. Melt Flow rate can be calculated efficiently with the help of “Melt Flow Index Tester”. The Melt flow rate of most common products polyethylene is tested at a temperature of 190° Celsius and polypropylene at a temperature of 230° Celsius. The melt flow rate is used to determine the mechanical strength and molecular structure of the plastics to produce high-quality of plastic products.