calculating viscosity from melt flow index

A variety of factors affect the precision and accuracy of a test. No matter what the procedure selected, it is common for two organizations to test the same material and come up with two different test results, setting off a search to determine the reason for the difference. Others may find that the alternative Melt Volume Flow Rate (MVR) procedure, offered by both standards, is more useful. Procedure B requires a “melt density” value and is best for companies that test the same material repeatedly and want to minimize the chance of operator error. Procedure A is typically most useful for companies that test infrequently, use a wide range of materials, use a variety of additives in their materials, or use regrind/recycled material. There is really no consensus as to which method is best however there are some guidelines that can be used to make a choice. Here are some reasons why such discrepancies occur and what can be done about them. The difficulty is that any two labs can easily come up with different results, making it difficult to determine whether a material meets a desired MFI spec. As part of their materials-inspection procedures, some processors use the test to determine the amounts of recycled material that can be used in their product while still maintaining end-product specifications. Resin suppliers, for example, look for MFI variations as a QC check to detect and troubleshoot variations in their polymerization and/or compounding processes. The MFI test is used widely among the various segments of the plastics industry. An extrusion plastometer, more commonly referred to as a melt indexer, is used to determine the MFI of virgin, compounded, and post-processed thermoplastics. The melt flow index (MFI), also known as the melt flow rate (MFR), determines the melt flow properties (measured in g/10 min) of a material at a specific shear stress (related to applied load) and temperature.

Calculating viscosity from melt flow index