This paper shows the strengths and limitations of using rheometer as a tool to carry out product development with clear outcomes and measurements. Individual tests derived can be installed as quality control tests. The general rheological behaviour of dispersions is presented and put into relation with the application of sprayability or levelling. Measurement procedures for sagging, levelling, sedimentation, brushability and the yield point determination are discussed and demonstrated on selected samples.
Rheometry characterises the sum of all components of a fluid and its interactions in respect of its mechanical properties. If one part of a formulation changes then the rheology of the product changes as well. Therefore rheometry is often used as the preferred tool to perform the final inspection of materials before leaving production. This advantage is opposed by the problem that rheometry cannot tell us which part is causing a different behaviour from the expected one unless there is very good practical experience available. Rheology does not replace chemistry or personal experience but it is an objective tool to judge overall product quality.
Rheology of dispersions (paint like fluids)
Many paints behave like dispersions or suspensions as seen in other products and substances.
Their mechanical behaviour expressed as viscosity and elasticity depends on:
• deformation, deformation rate
To fully characterise a fluid the influence of these parameters has to be know in order to predict the response under different applications.
A copy of this application package note is available by quoting reference no: HA-016