The correlation of the non‐newtonian flow of polymeric melts with the theories of Bueche

Bueche and Harding [J. Polymer Sci. 32 177 (1958)] obtained an empirical “standard flow curve” to relate viscosity and shear rate by using a particular poly(styrene) solution and positioning the flow curve on a dimensionless rate of shear axis via the viscosity average molecular weight, M V and Bueche's expression for the relation time, τ, where\documentclass{article}\pagestyle{empty}\begin{document}$$ \tau = 12\eta _{\rm o} {\rm M}_{\rm R} /\pi ^2 {\rm RTC} $$\end{document} Here R is the gas constant, η o is the low rate of shear Newtonian viscosity, T is the absolute temperature, C is the Concentration in grams per cubic centimeter, and M R is te molecular weight which determines the relaxation time. Bueche implies by his standard curve that M V correlates with M R . In Gereral, it was found that: 1) M R does not equal M V but it is usually significantly lower than M V or M W ; (2) the value of M R increases with increasing polymer concentration and temperature; and (3) the shapes of the flow curves are slightly different from the shape of the standard curve. A survey of the data available in the lon the flow of polymer melts supports these conclusions. Thus, the Bueche‐Harding method can only give semi‐quantitative help I predicting the flow behavior of polymeric melts.