Hello dear all,
I wanted to ask if there are any recommendations on any simple alternative ways to find Melt Density Value for the ISO 1133 MFI (MFR and MVR) tests?
So far I've come across three methods,
1- Alternating between MFR and MVR: After two tests are being done simultaneously, melt density could be get from the formula but it may not be feasible considering amount of varying compound materials'.
2- PVT diagram: Best option, but you may need an extra apparatus in order to find the value from injection moulding.
3- In reference, https://youtu.be/xLU2bKX_Enw?si=T3Aftj03sWoEukWf: It seems like a simple solution, but I'm not sure if it corresponds directly as melt density is the value in 0 MPa and should be the test temperature of MFI.
Kind regards, thanks in advance
Melt density is a function of temperature and pressure.
The pressure in Method 1 can be estimated from Weight and piston diameter but is not constant during measurement. Friction is present and affects the results. If you need just an approximated value, it is Ok.
The method 2 is the best. If you need density as a function of temperature and pressure you have to use such a device.
The method 3 is an approximate one as method 1. The effect of pressure during injection is not constant and is not considered there. If you do not measure it, the result will be different depending on the mold you use. One possibility could be just measuring the shot weight coming out from the nozzle and using the injected volume as explained in the link you provided. The pressure during injection will vary but not so much as if you use a mold.
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