Rheological – geological – but not mythological…


Pluto (not the Disney character – that’s another story) is a word that provokes emotion and comment. This ‘Planet X’ discovered in 1930 by a young graduate student Clyde Tombaugh, never fails to excite the science in all of us.

Demoting Pluto as a ‘real’ planet to a ‘dwarf’ planet a few years back attracted controversy with a huge public outcry and input for and against – the case for demotion was made mainly by a small bunch of political astronomers, it has to be said, so you can see I’m  not sitting on the fence on this one.

From a science perspective, the recent ‘fly past’ by the NASA New Horizons probe provided a multiplicity of stunning pictures that will be filtering in with full resolution throughout 2016. Wow!

If you’ve failed to be excited by what has been shown in geological and image terms, then you must be on another planet……. One of the latest images from the probe (now an incredible 3.3 billion miles from earth and traveling at over 32000 mph) evokes our theme of “Just follow the particle”.  This theme indicates which of Malvern’s plurality of technologies can be brought to bear on a customer’s problem or problems to provide insight and understanding.

The concentration, size, shape, particle charge all ultimately affect the flow properties and hence rheological properties of any formulation be it polymeric or suspension. Following the (flow) route and ultimate fate of the particles is an absolute necessity in any process and one that Malvern’s technical team always takes an interest in.

The description of the Pluto image states “In areas where the reddish material is thickest and the surface appears smooth, the material seems to have flowed into some channels and craters. Scientists say tholin (note: class of heteropolymer molecules formed by solar ultraviolet irradiation of simple organic compounds such as methane or ethane) deposits of that thickness aren’t usually mobile on large scales, suggesting that they might be riding along with ice flowing underneath, or being blown around by Pluto’s winds”.  Flow on Pluto! On earth scientists study the flow of rock (very low shear rates) in and around the mantle in order to understand plate tectonics.

Look for an interesting 2012 paper in Nature called “Modelling the rheology of MgO under Earth’s mantle pressure, temperature and strain rates” by Patrick Cordier and coworkers.  In there you’ll find terms we’re all familiar with on our Kinexus rheometer  – plastic yield, shear stress, shear rate, and more Greek letters than an Athens’ post office…. Soils and sediments scientists measure the particle size of their systems in order to look at sedimentation processes in lakes and on the sea floor. On earth we have glaciers and even whole continents (Antarctica) perhaps now floating on ice underneath rather than rock and thus moving even more quickly into the sea as temperatures rise.

So, go with the flow. Follow that particle!  Which of Malvern’s products help you explain the phenomena such as flow encountered on a daily basis whether on earth or Pluto?  We could be talking of paints, polymers, squeezing toothpaste out of a tube.

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