I am planning to find out the rheology using cross model. But, firstly, I should generate a flow curve of polymers with the mentioned parameters and without any help of instruments (rheometer, viscometer etc) . The whole process is done through extrusion. Any help would be appreciable. Thankyou in advance
I guess people may get confused about your questions. The viscosity is a material property, and how can people know or calculate a material property without actually measuring it with instruments (rheometer). My point is you have to measure it anyway or look for the literature.
So my second guess for what you are actually asking is: how to calculate the apparent viscosity of polymers during the extrusion. Well, if you know the parameters for your polymer in the cross model, you can have this constitutive equation simulated in any fluid dynamic software for specific geometry you want. Given a specific external input, then you can do integral (or ensemble average) over your specified domain for apparent shear rate and stress and then you can back out the apparent viscosity.
If you get/extract some data from your extruder, you can theoretically generate a curve similar to flow curve by means of mathematical approaches. It is a well-known fact that shear rate is related to screw speed and shear stress is related to torque for an extruder or a melt processing device. The most challenging issue in your case is the estimation of shear stress because torque of an extruder is a very rough/average value and depends on parameters which are varied in a wide range. You should have full knowledge of geometric detail and temperature profile throughout the barrel.
Good Luck...
I would use theoretical methods such as Density functional theory (DFT) or any similar techniques. For more information you may refer to the following paper:
DFT-based theoretical prediction of intrinsic viscosity of polymer solutions
DOI: 10.1080/1062936X.2018.1539035
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