Tutorial Rolie-Poly

Non-Linear flow prediction

1. Start RepTate and create a new NLVE Application :

   

2. Drag and drop shear (.shear) or uniaxial extension (.uext) data files, e.g. all the .uext files from the folder data/DOW/Non-Linear_Rheology/Start-up_extension/.

   The first column of the file should contain the time and the second column the stress (shear, or tensile, stress growth function).

   

3. Select the “RoliePoly” theory and press to create it.

   

   At this point, you need to setup the relaxation times, \(\tau_i\), and weights, \(g_i\), for each mode \(i\). You can:

   • Input them manually by clicking:

     

     then select the number of modes, enter the values and click “OK”, then “Minimize Error” .

   • Alternatively, it is possible to copy the values from a file or spreadsheet from and external program and paste the values into the “Edit Modes” table. Note that you should adjust the number of modes before pasting the values.

   • Obtain the Maxwell modes from a different RepTate application (LVE, TTS, G(t)). In this tutorial we will import Maxwell modes from a LVE application.

4. Create a new LVE Application and open the linear viscoelastic data file corresponding to the same sample at the same temperature. We use the file data/DOW/Linear_Rheology_TTS/DOWLDPEL150R_160C.tts. Then, we create a new Maxwell theory and “Minimize Error” :

   

5. Return to the NLVE application and now click . We want to import the 6 Maxwell modes of the “LVE2” app. Select from which theory you want to import the modes and click “OK”. Then click “Minimize Error” to find the best values for the tauR parameters:

   

6. Click the button to show (or hide) the linear viscoelastic envelope prediction:

   

7. The number of stretching modes is given by . \(N_\text{stretch}=0\) means that the non-stretching version of the Rolie-Poly model will be used for all modes. See Rolie-Poly equation for more details. So far, the calculations were done using “infinitely stretching chains” . Click that button to use finite extensibility . The maximum extensibility parameter lmax is now present in the parameter table. You can change its value and click “calculate” to update the theory predictions: