What is a non-newtonian substance? Is this some fad that
I've somehow been left out of?
I don't know about a "non-Newtonian substance" is in general, but a
non-Newtonian fluid is one whose viscosity (resistance to flow) changes in
response to some factor besides temperature. For example, a mixture of
cornstarch in water flows like a regular liquid if you pour or stir it
slowly, but if you stir it vigorously, it "sets" and acts more like a
non-flowing solid until you stop stirring it. This is a phenomenon known as
Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
A Newtonian substance behaves according to Isaac Newton's models of reality,
Isaac Newton's Laws of motion. A non-Newtonian substance is extreme enough
so as to require something such as relativity or quantum mechanics to
describe how it acts. A substance made of gluons would qualify as
No Fad -- Not Left Out!!
A NEWTONIAN fluid is a fluid in which the rate of shear -- think of rate of
shear as the motion of the body of fluid -- is proportional to the shear
stress -- think of shear stress as the applied force. The reason for these
rather abstract definitions is because there can be so many configurations
of fluids and sources of force. The key is the proportionality of motion
There are many kinds and combinations of non-Newtonian fluids. Some familiar
examples are: WATER = newtonian. House paint = shear thinning. That is it is
viscous when not stirred but flows smoothly on the brush with minimal
"drag". Certain muds are shear thickening. You can run across them, but
don't stop or you will sink in.
There is an enormous fascinating technology surrounding non-Newtonian
behavior of fluids. I would suggest you try to find a copy of Surface
Chemistry by Adamson in the library.
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Update: June 2012