Marlene Jegeborn var inbjuden som föredragshållare för en timmes föredrag med titeln:
”An Introduction to Rheology with special reference to paint applications”
Abstract:
Paints used to be easy to predict with just a viscosity number, but as paints went from being “bulk” products into “high-tech” products they also became more complex to predict. In the old days viscosity could predict reasonable well the flow properties and the behaviour of the end user paint. But, paints which are easy to predict with just a viscosity number are rare today.
Paints have become more complex due to environmental, economically or process driven reasons. Water borne paints are more complex (unpredictable) than solvent-based paints. All raw material changes the paint’s behaviour i.e. the use of cheaper raw materials to produce low cost paints or, for that matter, premium paints with expensive raw materials and designed behaviour for better flow properties. Another example of a designed behaviour is long term stability or transportation stability. On top of these adjustments is the inconsistency of variations in batches of raw materials. Any change of the raw material (particle size/shape, binder Mw/MWD etc) or any change to the recipe will affect the flow properties of the paint. The question is: – how much and how much is too much?
In addition to variations in raw materials, the same paint also undergo a large variation of process conditions; from pumping and mixing to application with relatively high speeds/shear rates to levelling and sagging with relatively low speeds/shear rates as well as temperature changes. It was a long time ago since the full behaviour of a specific batch of paint could be related to a single viscosity “dot”. Today we use sophisticated rheometer to predict the paint´s behaviour by measuring the structure strength at given rates/stresses, temperatures and time scales
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