MFR
What does MFR stand for?
Melt flow rate
What materials do we typically NOT see MFR testing for?
Those highly affected by moisture: commonly nylon and polyesters
What does hygroscopic mean?
Material absorbs moisture from the air
What units is MFR given in?
g/10 mins
False, very low shear test
T or F: you should never need to dry PP
False: drying may still be recommended for surface moisture even if the PP itself doesn't pick up moisture
What does MVR stand for?
Melt volume rate
An increase in shear rate results in a non-linear decrease in viscosity
Rank the following nylons by moisture pickup from the most to the least: PA 6, PA 4/6, PA 12
PA 4/6
PA 6
PA 12
Explain the difference between MFR & MVR
MFR is the weight of material that extruded out in the 10 minutes whereas MVR is the volume displaced within the testing barrel in 10 minutes
False, ABS shear thins more showing a greater decrease in viscosity at injection molding shear rates compared to PC
If we overdry nylon what can happen?
The material will not flow as well and exhibit brittle behavior
Can I compare MFR and MVR values? If so, how?
Using melt density we can convert from MVR to MFR (MVR in cm³/10 mins X MD in g/cm³ = MFR in g/10 mins)
If different materials cannot be compared, what is the purpose of MFR testing?
To show differences in viscosities for the SAME material or could also be used to show a change after processing (result of degradation in our customer's process)
Which material would pick up the least amount of moisture? PARA, PPS, PA 6, or a PBT?
PPS