Ceramic Rheology
Ceramic "fluids" (slips, suspensions, pastes) have a wide range of flow properties. These flow properties vary not only by binder and filler constitution, but by manufacturer and by production batch to batch. It is accepted that ceramics vary, and accepted that some control of the variation should be employed.
In terms of flow characterisation, this leads to two major questions :- 1. What is the rheology of this particular ceramic fluid ? and 2. What has changed between batches ?
Ceramic fluid rheology covers a number of properties - shear viscosity, wall slip, extensional viscosity yield stress. Each of these properties plays a prevalent role at different points in a process ( request DrRheology Technical QuickSheet for extrusion, injection and spraying of ceramic suspensions and pastes). These properties can vary independently and so it is important to characterise the correct property for a given application.
DrRheology offers the measurement of a range of rheological properties. We can also model a process and show the relevant changes that can be expected.
Going about the job of testing.
Testing always can be classified as either 1. We don't know what it is, and we're finding out about it. or 2. We know what it should be, and we're just checking. The first kind of testing requires some time to check on the fundamentals - is the flow stable? is the temperature optimum ? does it degrade? is it repeatable ? is there significant inhomogeneity ? The second kind of test is generally referred to as QC testing, where we simply repeat what we did before.
Testing for processability should generally be done at rates, pressures and temperatures that resemble those found in the process. For this kind of work, we will generally recommend a capillary rheometer or an extruder. For sedimentation in suspensions we will generally recommend a rotational rheometer. We can supply results as raw data, or as a model. We can also supply calculated and CFD models of the flow in a process.
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Measured on lab rotational rheometer |
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Measured on lab capillary rheometer (request poster) |
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Measured using capillary flow |
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Measured on lab capillary rheometer |
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Measured using contraction flow |
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We can calculate :- |
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We can train your staff to make a range of measurements and on how to interpret and use the data. |
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PIM materials when tested on a rheometer gives the user a lot of understanding about the material: - how good the formulation is, how stable the formulation is, how repeatable the material is in batch production, how the material can be processed. |
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