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Test Calculations
Calculations: Method A
Calculations for the Method A test are:
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:
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 corre
lation 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:974179
Rev: 0918 ECO: 49667
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