M0726(2):LMFI Series 5000 Lab Melt Flow Indexer
28
English 02/2014
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.
Barrel Charge Size in Grams
Melt Density->
MFR g/10 min
0.75 g/cc
1.0 g/cc
1.2 g/cc
0.1
2.7
3.6
4.4
0.2
2.8
3.7
4.4
0.5
3.0
3.9
4.6
1
3.3
4.2
4.9
2
3.9
4.8
5.5
3
4.5
5.4
6.1
4
5.1
6.0
6.7
5
5.7
6.6
7.3
6
6.3
7.2
7.9
7
6.9
7.8
8.5
8
Plug
8.4
9.1
9
Plug
9.0
9.7
10
Plug
9.6
10.3
11
Plug
Plug
10.9
12
Plug
Plug
11.5
13
Plug
Plug
Plug
