From lab to production,
providing a window into the process
-30-
4.) Perform a sample purge of material. Once done, clean thoroughly.
5.) Loads 6 grams of sample and perform run. Perform the test 3 times to obtain a
repeatable MFI and record the value.
6.) Perform a run using parameters in step 3.
7.) After the run, an Intrinsic Viscosity will be displayed and printed.
After each run:
Clean Barrel
Clean Die (remove first)
The Amount of Sample
ASTM gives a recommendation of how much material to put in the barrel to perform a test.
However, by determining the proper charge and controlling it from run to run. Testing can
be made easier and more reproducible. The distance from the top of the die to the piston’s
first scribe mark is about 5 cm. Filling the barrel up to the first scribe mark is the minimum
charge needed to run a test. During the recommended 6 minute melt time, some material
flows out of the die so a larger charge is needed. The best situation would be to add just
enough material, so that, during the melt time, the plunger slowly falls and is just above the
first scribe mark when the 6 minute melt time has expired. In this way, the required 6 minute
melt time is satisfied and there is no excessive waiting before the first cut is made (or timing
flag starts in timed tests). A conservative estimate for charge weight can be calculated if an
approximate melt flow rate and melt density for the material are known by using the
following formula:
Charge Mass = 3.6ρ+0.6*MFR
Where the charge mass is in grams, ρ is the melt density in g/cc and MFR is the anticipated
melt flow rate in the typical units of g/10 min. This equation will tend to slightly overestimate
the charge needed. For a Polypropylene, with an anticipated MFR of 3.5 at 230 C, using the
melt density of 0.738 from the above table, the estimated charge mass would be:
3.6*0.738+0.60*3.5=4.76g
In our lab, we have found that 4.6 grams is a good charge for a 3.5MFR Polypropylene
sample. The equation overestimates the charge since is assumes flow from the instant the
material is packed into the barrel. The following table shows an estimate of charge weight in
GRAMS based on anticipated MFR (g/10 min.) and melt density (g/cc). Where the word
“PLUG” appears indicates you cannot put enough material into the barrel such that after 6
minutes there would be enough left to test, the barrel must have a flow plug inserted at the
base of the die to keep the material from escaping.
P/N: M0726(3)
| Rev: 012020 | ECO: 51182
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