Tag Archives: melt flow index

Viscosity, Part 2: Melt Flow Index

In our last tech tip, we started a three phase discussion about viscosity. The first phase talked about how capillary rheometers are used to characterize the viscosity of plastics at a wide range of shear rates and temperatures. However, due to a variety of reasons most people in the injection molding industry prefer to use a simpler device when talking about the viscosity of a plastic – the Melt Flow Index machine. One should be aware that even though MFI is the dominate method used to characterize how plastic will flow in a mold, it does not actually provide a measure of viscosity.

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