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The flow behavior of paints and varnishes plays a key
role in the processing stage. Apart from other parame-
ters, viscosity is an important variable of a paint system.
Viscosity has a physical significance as a measure of the
internal friction of a liquid which is caused by intermole-
cular interactions. The shear forces in a flowing material
depend, among other factors, on the deformation
velocity.
For certain liquids viscosity is a material constant that
only depends on temperature and pressure. This group of
materials is termed Newtonian liquids.
The Newtonian two-plate model shows the ratio of shear
stress to the velocity gradient. This factor is ca lied dyna-
mic viscosity.
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