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-26-
Test Calculations
Calculations: Method A
Calculations for the Method A test are:
MFR =M 600
T
where M is the mass in grams of material collected over time T in seconds. The MFR value has
units of g/10 min. (grams/10 minutes).
Calculations: Method A/B
In a Method A/B test both a Method A test and Method B test are performed on the same
charge of material. The melt flow rate, derived from Method A, is equated to the Method B flow
equation and solved for apparent melt density. The value in doing this test is obtaining a valid
apparent melt density which can later be used in a Method B test (no manual cuts of extrudate
nor weighing) to achieve results equivalent to Method A (operator must make manual cuts and
weigh sample).
Calculations for the Method A/B test are:
Method B MFR =
πR2Lρ 600
TB
Method A MFR = M 600
TA
ρ = MTB
πLR2T
Where R= radius piston (cm), TB (sec) is time to traverse the Method B distance L, L = Method
B length of flag (mm), M is the mass in grams of material collected over the time TA in seconds.
MFR has units of g/10 min. (grams/10 minutes). ρ (g/cc) is called the apparent melt density and
is defined by equating the methods; the Method B flow rate must equal Method A.
This apparent melt density definition forces the two test methods to agree. DYNISCO
POLYMER TEST recommends taking an average of apparent melt densities from at least five
separate A/B tests on representative samples of polymer. This average apparent melt density
can then be used for Method B tests to get Method A (MFR) values without having to make
cuts! It is called an "apparent melt density" because it is actually a correlation coefficient that
forces Method A and Method B to agree. If, during the A/B test, there was no leakage past the
plunger tip and the extrudate was bubble free and other minor factors did not occur, then a true
melt density could be assessed. All lengths are in mm.
P/N: M0726(3)
| Rev: 012020 | ECO: 51182
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