Polymer viscosity

Viscosity is a measurement of the resistance of a material to flow.
A material that can flow eaily has a low viscosity whereas a material that can not
flow easily has a high viscosity.
Quantitatively,it is defined as:
u(y)=r/y
Where u is the shear viscosity in pasec,r is shear stress in Pa and y is the shear rate in 1/sec.
Polymers exhibit shear-thinning behaviour in suc a way that as the shear rate increases,
the shear viscosity decreases as indicated in figure 1.