Observations on Experimental Data

As can be seen, the shear viscosity function is well investigated over six decades of shear rate for the virgin polystyrene and the filled compounds up to 18% Ti02 content. Whilst the 38.6% compound is only documented in a shorter shear rate range (i.e., 1-1000 s i), the occurrence of a yield stress behavior that depends on the filler level makes however no doubt. 

In the high shear region, the shear thinning behavior is not much affected by the presence of the filler, since the flow index n seems to be the same, whatever is the filler content. Presumably, the characteristic time Xq is also not depending on the filler content. 

It follows that, for the filled compounds, only Oj r o and a must be fit to experimental data 

8 Fitting the Virgin Polystyrene Data with the Carreau-Yasuda Model 

Guess parameters for nonlinear fitting algorithm (GenFit function) 

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In a noteworthy departure from the approach used in the theoretically-based equations of state, Arends L42,43] developed a phenomenologically-based equalion-of-state for polymer melts directly from observations on experimental data for five thermoplastic polymers and then attempted to extract physical meaning from this equation. 

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