Melt Flow Index Testing (MFI)
Melt Flow Index is an analysis method that determines the ease of flow of plastic materials.
Melt flow rate depends on molecular weight, additives, and other ingredients. The melt flow index value allows for direct comparison of materials to each other and is a valuable tool for quality assurance.
The sample must be “meltable” in order to be evaluated using the MFI instrument. To charge the instrument with the sample, the sample has to have a particle size that is on the order of about 3-mm or less so that it can be loaded into the barrel portion of the instrument. So, typical plastic pellets are an appropriate particle size. The measurement involves weighing the mass of a plastic that flows from the instrument over a timed interval. Some polymer materials (polyethylene for bag applications) have such high flow rates that the MFI method in that case must be an automated system to obtain reliable results.
Thermoplastic materials can be evaluated using the MFI method of analysis. Some examples of materials that are evaluated include:
An MFI sample must be capable of being melted. A single MFI determination requires about 10 grams of material, and samples are typically evaluated in triplicate. Usually a few trial runs are needed to set the proper mass charge for the tester, so ideally we like to have about 100 grams of sample.
Typically samples are in the form of:
*Because we can convert manufactured products into plastic powder, the melt flow analysis can be reliably determined for finished products.
Contact us to talk through your specific sample considerations.
Melt Flow Index is a very valuable test for quality assurance.
Work we've done with Melt Flow Index includes: