Concentration regimes Huggins equation

The relative viscosities of polymer solutions are measured at different concentrations and a plot of the reduced viscosity versus concentration is made, in order to extrapolate to zero concentration. The concentration dependence of the viscosity of polymer solutions, in the dilute regime, may be expressed by several linear equations. For practical extrapolation to zero concentration, the most commonly employed are the Huggins equation ... 

The defining Equations 3.22 and 3.23 produced by Huggins (1942) and Kraemer (1938) apply only to polymers at low concentrations or, more strictly, polymers in the dilute regime, in which interactions between polymer molecules are negligible. Many other empirical equations have been proposed which describe the variation of the polymer viscosity with the concentration at higher concentrations where polymer-polymer molecule interactions are more significant. For example Lyons and Tobolsky (1970) proposed the following empirical form ... 

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