M0726(2):LMFI Series 5000 Lab Melt Flow Indexer 25
English 02/2014
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.
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