Viscosity Master curve for different polymers

Graessley [71] suggested that it should be possible to describe the viscosity of all monodisperse, linear, entangled polymers by a single universal curve, if data are plotted as  

We note that % is the number average relaxation time originally defined by Eq. 4.57. Vinogradov and Malkin [72], Berry etal. [73] and Attan6 etal. [74] reported generalized plots of 77/770 versus y J° y  

The original Doi-Edwards model predicted that the shear stress in steady shear increases from zero and goes through a maximum. This type of behavior has never been observed, and this remained a basic deficiency of tube models until relatively recently when lanniruberto and Marrucci [76] introduced the concept of convective constraint release (CCR). In steady shear flow, molecules on neighboring streamlines are moving at different speeds, and this carries away entanglements at a rate comparable to the reciprocal of the shear rate. An early version of this idea that predates the tube model was presented in 1965 by Graessley [4]. 

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