The FT4 Powder Rheometer® was originally designed with one purpose in mind - to characterise the rheology, or flow properties, of powders. This remains a primary function today, but the instrument, accessories and methodologies have been continuously developed to the point where the FT4 is now considered a universal powder tester.
In addition to the patented dynamic methodology, where a powder’s resistance to flow is measured whilst the powder is in motion, the FT4 also includes a shear cell for measuring the powder’s shear strength, a wall friction kit to quantify how the powder shears against the wall of the process equipment (in accordance with ASTM Standard D7891), and also accessories for measuring bulk properties, such as density, compressibility and permeability. This range of measurement capabilities makes the FT4 a truly universal powder tester and the world’s most versatile instrument for measuring and understanding powder behaviour.
FT4 Powder Rheometers are installed around the world in a diverse range of industries including chemical, pharmaceutical, additive manufacturing, toners, foods, powder coatings, metals, ceramics, cosmetics and many others. They deliver data that maximise process and product understanding, accelerating R&D and formulation towards successful commercialisation, and supporting the long term optimisation of powder processes.
The FT4 is supplied with a variety of accessory kits, including the Aeration Control Unit, which allows fine control of air flow through powders under test to evaluate fluidisation behaviour. The bulk properties of powders are affected by the presence of entrained air which fills the spaces between particles. The removal or addition of this air can radically change the flow properties of a powder - often by a factor of 100 or even 1000. When aerated, the contact between particles is reduced and less energy is required to cause flow. For some powders, complete separation of individual particles results in fluidisation when the powder behaves as a fluid. This reduction of flow energy is described by the Aeration Ratio (AR), which can be measured automatically using the Aeration Control Unit on the instrument.
The Aeration Control Unit is under the direct control of the FT4's control system allowing the following types of automated testing, with no operator involvement:
- Aeration or fluidisation assessments to determine response to increasing levels of aeration - up to fluisation velocities where appropriate
- De-aeration testing to determine how readily a given powder releases entrained air following aeration
- Permeability profiles derived from measurements of pressure drop across a powder bed at varying levels of consolidation stresses.
With an operating range down to a velocity of 0.02mm/s, this Unit also delivers the high degree of control at very low rates that is essential for characterising powders sensitive to the addition of a very small quality of air.