As far as I understand Moldflow uses a fixed value for a temperature that defines the material to be in solid or melt phase and the frozen layer will be determined by this temperature. Its proper definition seems to be crucial to determination of flow fronts and pressure predictions. So the questions arises, how does Moldflow determine this no-flow temperature and is there a way to influence it?
Thank you very much for any hint!
(Using Moldflow Insight 2013)
Solved! Go to Solution.
I had a look and compared two types of grades according to data from material properties window.
Generic PP: semi-crystalline
Ttrans = 111 C
b5 (pVT) = 388.75 K = 115.6 C
D2 (CrossWLF, Tg) = 263.15 K = -10 C
Lexan 105: amorphous
Ttrans = 144 C
b5 (pVT) = 415.98 K = 142.83 C
D2 (CrossWLF, Tg) = 417.15 K = 144 C
For amorphous grades the Ttransition may be estimated by the Tg.
For semi-crystalline grades the Transition may be estimated by the Tcrystallization (Ttrans ~ Tc which is b5 from the pVT, you can query the data point on the pVT plot just when the specific vol. drops exponentionally from the melt phase to the solid phase).
However, I noticed that sometimes Trans < Tc (b5). And Tc is a dynamic property and such depends on the cooling rate.
Hope you find this useful...
kind regards, Martin
the Transition Temperature is the temperature at which the polymer transitions from molten state to solid state.
The method used to test this is a standard method:
ASTM D3418, using DSC, Differential Scanning Calorimetry.
You can edit/modify the transition temperature of the material.
In process settings: Advanced options...
Molding material: Edit...
tab Rheological Properties
This way of manipulating material data is basically not recommended.
This might affect other material data properties or invalid data, affecting analysis results.
Ok - so you say, in Moldflow the transition temperature of the material one finds in the 'Rheological Properties' tab equates the no-flow temperature used in the solver algorithms? I am just asking because, according to literature, some solvers also use no-flow temperatures determined from viscosity profiles.
Many thanks for your support!
right, the Transition Temperature data field is used by flow solver when the polymer transitions from molten state to solid state takes place.
So you could use a No-Flow temperature.
Transition Temperature and No-Flow temperature basically means the same, but are measured differently.
In Moldflow words I would put it as:
1)Transition Temperature uses DSC method.
2)No-Flow uses a capillary rheometer (Autodesk Moldflow Plastics Labs has developed such a device in the past,
where you turn off the heating of barrel, to find and measure temperature when melt no longer extrudes.)
Autodesk Moldflow Plastics Labs