What the number measures
Melt flow rate is the mass of polymer that passes through a specified die in a given time under stated conditions, reported in grams per ten minutes. Temperature changes the resistance of the melt to flow. The piston load changes the force driving it through the die. A value measured with a higher load or at a different temperature cannot be ranked directly against a value measured under another condition.
Reading a resin data sheet
Put the test method, temperature and load next to every reported value. Check whether the result is mass flow or volume flow, and compare like with like. For moisture-sensitive grades, specimen handling and preconditioning can also affect the comparison. If the two data sheets use different conditions, ask for data at a common condition appropriate to the materials rather than applying a universal conversion.
For a thin-walled compact shell, MFR helps screen lots or grades. A mold trial still has to show how the chosen resin fills that geometry and what the finished part looks like. Actual flow varies with the gate, melt temperature and shear in the cavity.
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