Extensional methods, comparison

For polymer melts, fiber spinning results can be compared to true uniaxial extensional viscosity data measured by rod pulling. Figure 7.5.7 shows such a comparison for a low density polyethylene. We see qualitative agreement between the methods but, a very strong effect of upstream history is evident in the fiber data. Both die extrusion velocity and residence time in the die exert a big influence. 

Figure 11.11 Comparison of the predictions of the DEMG model (solid line) and MLD model (dashed and dotted lines) to experimental data (symbols) for the uniaxial extensional viscosity rif (e) versus extension rate f. The data are for a 6% solution of 10.2 million molecular weight polystyrene In diethyl phthalate at 21 °C.The parameters used In the MLD and DEMG theories are G 5 = 294 Pa for both models = 21 s, and Tj = 0.51 s for the DEMG theory, and = 83.4 s, and Tj = 1.08 s for the "Mllner-McLeish" method of obtaining the time constants for the MLD model (dashed line), and Tj = 123 s, and Tj = 1.58 s for the "Doi-Kuzuu" method (dotted line). From Bhattacharjeeeta/. [49).

For linear as well branched mLLDPEs, it has been revealed that both, corrected Cogswell and Binding methods have very good capability to describe the extensional viscosity which has been confirmed by the direct comparison with SER extensional viscosity data. 

---