Home     Calculate the Viscosity of a Polymer Melt or Solution over a Temperature Range

For the polymer chemist the glass transition temperature (Tg) is a useful property. The glass transition temperature of the polymer or oligomer can be related to the viscosity of the polymer solution and the viscosity of the polymer at different temperatures. The Tg of a polymer can be understood in terms of the free volume concept. A polymer at Tg or below its Tg has no free volume for the polymer chains to move. Heating a polymer above its Tg increases the free volume and makes the mobility of the polymer chains possible. This concept of the free volume is expressed in the WLF[i] equation (William, Landel and Ferry). Below is a modification of this equation, which uses universal constants according to Nielsen[ii]. These universal constants are reasonable accurate for most polymers. If a deviation is found for a series of polymers these constants can be readjusted. 

Measured Data


WLF equation 

Log η= C-A(T-Tg)/(B+(T-Tg))



VISC cps


VISC LOG T-TG Tg C   C= Universal Constants for most polymers
 Polymer A   A=
 Polymer B   B=
Enter desired range                  
 Delta, temp

Calculated Value

Viscosity, cps Comp A  
  Comp B  
Log (poise) Comp A  
  Comp B  

[i] M.L.Williams, R.F.Landel and  J.D.Ferry, J.Am.Chem.Soc.77,3701(1955)

[ii] L.E.Nielsen, Polymer Rheology, Marcel Dekker, 1977,pp.33,74,133

Automatic recalculation 

Last edited on:

October 21, 2010

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