The American Society for Testing and Materials (ASTM) defines and sets standards to assure the quality of products. Over 11,999 ASTM standards work on an international level, including tests specific to plastics. It provides support to the customers to have confidence that the products they purchase will perform as per expectation.
One of the ASTM test procedure for plastic is a test for Melt Flow Index or Melt Flow Rate (MFR). Melt flow rate evaluates the rate of extrusion of thermoplastics through an aperture at a defined load and temperature. The test provides a means of measuring the flow of melted material. The test result can be used to differentiate between grades of the same polymer to determine the extent of degradation of the plastic as a result of heat. MFR is an indirect measure of molecular weight, with a high MFR related to molecular weight and the reverse.
In Melt Flow Index Tester, the test is conducted with approximately 7gms of the polymer that is loaded into the barrel of the melt flow indexer. It is heated to a particular temperature that depends on the type of material being tested. A weight is mentioned for the material that is attached to a plunger and pressed in a downward direction with a force through a die. A extrude is collected and is weighed separately. The sample data helps to calculate the melt flow rate value and expressed in g/10 min.
MFI Tester is applied to the mass of polymer, in grams that flow in ten minutes by a narrow outlet of a particular diameter and length through pressure exerted through weights and temperature. A quality of polymer can be defined as the one with MFI high enough so that the molten polymer can be manufactured into the desired article but it should be low enough that the mechanical strength of the final product is retained for a long time. Melt flow index machine is the need for all the polymer industries to ensure high quality in the production line.
There has been increasing pressure on the plastic manufacturers to create quality products. So, most of them have started using a testing instrument to measure the quality of raw material and the finished product. The machine helps to measure the properties like shear rate, viscosity, shear stress, and the molecular structure. The main property is to measure with melt flow test is its flow resistance and the viscosity of the polymers at specific load and temperature.