PowderRheology

Powder Flow Measurementwith MCR Rheometers

Working with powder can be difficult, particularly when it comes to processing and storage. Most of these challenges are related to powder flow. Powders not only create difficulties in processes, the intake and predelivery control of powder is highly important as well. To ensure efficient quality control and smooth powder processing, you can simulate and determine powder flow under various conditions turning an MCR rheometer into a powder rheometer with the new Powder Cell.

A wide range of factors influence powder flow – such as particle size and shape, chemical structure, humidity, temperature, packaging behavior, static charge, surface morphology, gas adsorption, air humidity and distribution of particle sizes. As a result, powders – as mixtures of solids, liquids and gases – are complex. This complexity can be simplified with one value: Cohesion Strength.

Cohesion Strength is the internal resistance of the powder to flow. Based on Cohesion Strength, you can predict whether the powder will flow through your process smoothly and whether the quality of your powder has changed.

The measurement curve converges to one Cohesion Strength value.

No matter which factor influences your powder, the established Cohesion Strength value will change.

Powder is everywhere …… and it creates challenges

Figure 1: Even a small amount of moisture can influence the flow behavior to a large degree

Figure 2: The shape of your particles can and will influence the flow behavior (same particle size)

Figure 3: Variation between batches can be represented accurately Figure 4: Grain size influences the powder flow (chemically identical powders with a slight difference in grain size)

Analysis with the MCR powder rheometer

Reproducible and reliable

� True powder rheology � Fluidization ensures reproducibility by clearing the “powder memory”

� Operator-independent measurements � Over 90 years of experience in smart engineering

� Usage of high-quality components � Optional pressure drop measurements

High throughput

� Results within two minutes � Interchangeable measuring cell � Automatic measurement program � Capable of measuring all kinds of powders (all Geldart groups)

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Easy

� Special powder template available for rheometer software

� Automatically performed calibration � Live visualization of measurements (with the software)

� Intuitive handling � Simple cleaning (cell dismantled within one minute)

� Support from worldwide Anton Paar service network

Economic

� Mutliple options with one device � Low operating costs � Fully automated one-click calibration

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Unique dust protection

The two-fold geometric barrier shields the bigger particles to keep them inside the measuring cell.

The air seal technology + a two-fold geometric barrier = a powder cell that is one hundred percent dustproof!

The air seal technology, in form of a permanent airstream, prevents even the smallest particles from leaking.

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Torque range: max. 300 mNm

Min. torque rotation: 10 nNm (air seal influence included)

Normal force range: 0.005 N to 50 N

Normal force resolution: 0.5 mN

Measurement systems: two-blade stirrer, Warren-Springs geometry, cylinder, profiled cylinder, further systems on request

Sample volume: min. 100 mL

Dust Protection Hood: d ≥ 5 µm particles, 100 % dustproof; 5 µm > d ≥ 1 µm particles, 90 % to 95 % dustproof

Supplemental equipment kit for scientific purposes (R&D) available containing:

Mass Flow Controller for software-controlled air velocity

Pressure Sensor to characterize the pressure drop across the powder bed, enabling high-end rheological characterization of fluidized beds

The Powder Cell is compatible with the following MCR rheometers:

MCR WESP, MCR xx1 series (all devices), MCR xx2 series (all devices)

Specifications may vary depending on the instrument

The Powder Cell’s unique Dust Protection Hood safeguards the operator and the instrument from fine and potentially hazardous powder even when it is fully fluidized. By combining the air seal technology and a two-fold geometric barrier, the Powder Cell is one hundred percent dustproof without any friction on the measurement axis and thus retains the MCR rheometer’s extraordinary accuracy and resolution down to 10 nNm and below.

You are able to safely and reliably quantify the most minuscule changes in your powder.

Specifications

Simplify complexity: Many applications,one Cohesion Strength value

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How can I use an MCR powder rheometer?

The MCR powder rheometer (an MCR rheometer combined with a Powder Cell) ensures the quality control of incoming and outgoing powders and bulk products. Additionally, it is highly useful for process monitoring and for promptly detecting changes in your powder and thus avoiding extra costs. You can gather even more data when using the Powder Cell in the scientific version (fluidization parameters, true powder rheology).

How reproducible are the measurements?

The reproducibility depends on the powder but the deviation is usually less than 1 %. However, small changes in the powder properties, such as water content or impurities, have a much greater influence on the measurement.

Can I also measure hazardous powders?

The Powder Cell can be sealed, is conductive, has no ignition sources and is therefore also a good tool for hazardous powders. Nevertheless, the measurement of hazardous powders is done at your own risk; we advise you to contact our product specialists before such operations.

Can I also measure wet powders?

Of course it is also possible to measure wet powders; due to its smart design the Powder Cell measures a wide range of powders and bulk solids. Depending on the powder and the application, you also get a lot of valuable additional information if required, such as the drying curves for wet powder during the drying process in the cell.

How long does a measurement take?

A single measurement itself takes about one minute. Including the preparation of the cell, the entire operation takes about two to four minutes. You can accelerate this by using multiple cells.

How can an MCR powder rheometer improve my process?

This setup helps you to perform quick but thorough and reliable quality checks of the powder as it is received. The MCR powder rheometer also helps you detect the quality of the final product and semi-finished goods swiftly and reliably to avoid further problems. If you are interested in a powder’s special flowing behavior, this can also be engineered with the help of the Powder Cell.

Can I perform advanced rheological measurements?

Of course. All advanced measurement modes used in liquid rheology can be applied to powders using the Powder Cell. However, to correlate rheology with precision pressure drop measurements you would need the supplemental equipment kit for scientific purposes.

Frequently asked questions

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