Fiber & Raw Material Engineering

Polymer Melt Flow Index (MFI) Predictor

MFI is an inverse proxy for melt viscosity and molecular weight. Higher MFI flows more easily and spins finer.

Extrudate Plastometer cut
g
s
Die & Melt Standard capillary
mm
g/cm3

Melt Flow Index

— g/10min

Mass extruded through the standard die in ten minutes

Flow Characteristics

Melt Volume Rate
— cm3/10min
Apparent Wall Shear Rate
— 1/s
Equivalent Throughput
— g/h

MFI is a single-point measurement at low shear. Fibre spinning happens at far higher shear rates, so use it to compare grades rather than to predict spinline behaviour.

Polymer Melt Flow Index (MFI) Predictor — free, with the formula and a worked example, at Textile School.