2- Melt Flow Rate (MFR) or Melt Flow Index (MFI)
It represents how much molten material can be pushed through a standardized hole, at a given temperature, under a given weight, in 10min.
A high MFR means the plastic is very fluid. A low one means it’s viscous.
This cannot be used as it is, but it will tell you if the grade is appropriate for extrusion.
- MFR < 10g/10min = extrusion grade
- MFR ~ 10g/10min = general purpose grade
- MFR > 10g/10min = injection grade
- MFR > 20-30g/10min = injection grade, extremely difficult to extrude
Limitations to the TDS
It is crucial to keep in mind that all the information available in a datasheet was obtained under very specific circumstances, and that it remains valid under certain conditions. This is especially true for the typical material properties, which are given with a reference to a certain test method, usually an ASTM or ISO standard. This means that for each of these values, the corresponding norm should in theory be read to understand the validity of the value. The appropriate and simpler approach is to keep in mind that none of the values should be taken “as granted”, but they can be considered good estimations.
It takes a bit of experience to translate the data from a TDS into extrusion settings.
You can find a complete practical guide about how to start an extrusion experiment after the quick reading of a TDS here.