Freeman Technology Web Presentation Series

Freeman Technology specialise in providing systems for the measurement of powder flow properties. Whether your interest is development, scale-up, processing or quality control, measuring and understanding powder flowability makes a great deal of sense.

With 10 years experience in powder flow and powder characterisation, Freeman Technology provides application know-how alongside its universal powder tester, the FT4 Powder Rheometer, providing world leading technology and solutions for understanding powder behaviour. The FT4 utilises its patented dynamic methodology, a fully automated Shear Cell and several bulk property tests, such as density, compressibility and permeability to quantify powder properties in terms of flow and processability.

Extensive application experience across all powder industries ensures that the FT4 is a proven solution to many industrial challenges, from formulation to tablet manufacture to hopper design.

From a processing perspective - productivity and quality are universal objectives. When powders are involved their characteristics can greatly affect the efficiency of the process. Understanding powder flow and powder properties is therefore very important. Examples of questions that can arise in everyday processing are:

  • Why is this batch a problem?
  • Will this alternative source of material be ok?
  • Will this powder transport ok by road?
  • Can powder flowability be improved by using a flow additive?
  • Is this new powder suitable for this (existing) process line?
  • How readily will this powder release entrained air?
  • Will this powder dose satisfactorily?

Understanding powder behaviour is also important in other contexts. For example optimising formulations to achieve favourable processing characteristics and establishing QC criteria so that powder flow performance can be verified at all stages of manufacturing.

Working with industry and providing answers to questions like the above using the FT4 Powder Rheometer is our business. If this is of interest to you – please read on.

Powder processing is challenging and has relied extensively on very experienced operators to overcome problems and ensure that production targets are met. Some formulations will be easy to process and others will be problematic. Batch to batch variability will be commonplace with certain products and ways and means of resolving these issues may have evolved from long experience.

Resolving the processing issue however, allows production to continue but usually does not provide an understanding of why powder flow problems occurred – what was the underlying cause? Inevitably it will recur and process efficiency will be compromised on an ongoing basis.

Our perspective is that learning from this experience and understanding the root causes of processing problems is now possible. This can be done by measuring the powder characteristics of powders that flow well and not so well. This applies to different formulations and to batches of material. Hence we can determine the optimum powder characteristics for each piece of plant whether a hopper or a tablet press. The compatibility of a new formulation with each item of plant can then be determined with confidence.

Powders are blends of solids, liquids and gases, usually air, and their flow properties or rheology, may be affected by perhaps 100 or more factors. These include particle characteristics such as size range and shape, environmental factors such as air content, temperature and vibration, and chemical interactions such as those which produce caking.

Powder flowability depends on all these factors and describes how easily a powder will flow. Broadly powders are either cohesive or non-cohesive. A free flowing powder is non-cohesive – particles are separate and when unconfined are able to move individually – for example dry sand when spilled. However, such powders may easily aerate and even fluidise so that control within the process becomes difficult or even hazardous. ‘Good’ and ‘bad’ are relative terms in powder processing.

Cohesive powders are not free flowing. Their particles attract each other and more energy is required to make them shear or flow. The agglomerates formed trap air which makes the powder spongy and compressible. However, they are dust free, not prone to segregation, unlikely to suffer attrition and will not fluidise, all of which may be advantageous. In a confined, slightly pressurised environment they are better able to flow round corners into the recesses of moulds for example, unlike free flowing coarse materials. However, cohesive powders are sticky and reluctant to flow from hoppers or into recesses on dosing machines. Generally they are more problematic during processing.

To summarise, quality and productivity depend on powder and plant characteristics being matched and this in turn, requires a comprehensive understanding of powder characteristics and powder behaviour.

The FT4 has become a truly universal powder tester offering powder flowability measurements, shear cell testing and bulk properties measurements in one instrument. The patented dynamic measurement of flowability pioneered by Freeman has been complemented by the development of a series of high-precision accessories.

During dynamic testing the rotational and axial forces acting on a patented helical blade are measured as it passes through a sample. Basic flow energy is determined from these data and is regarded as a measure of the rheology or resistance to flow of the powder. A unique conditioning step eliminates the influence of processing history so that extremely reproducible baseline measurements are generated for aerated, conditioned and consolidated samples.

Combining dynamic measurement with bulk properties and shear properties measurements allows the characterisation of powders in a range of complementary ways. For example, bulk density, permeability and compressibility can be determined easily and a family of shear cell accessories deliver accurate, conventional shear stress data for samples down to 1ml.

All testing is automated and utilises the unique conditioning methodology so that exceptional levels of reproducibility of data are attainable. A library of test programs are provided and the test data is stored securely in binary file format.

With the FT4 you can:

  • Study the flowability of conditioned, consolidated and aerated powders
  • Measure bulk density, permeability and compressibility
  • Generate high precision shear strength data
  • Quantify the impact on flowability of many variables such as moisture, segregation and attrition
  • Optimise formulations
  • Construct a database of powder characteristics for all your powders
  • Predict processability
  • Analyse abnormal process behaviour
  • Establish QC criteria for raw materials, intermediates and final product
  • Detemine optimum powder characteristics for each item of plant

Most powder processing companies have vast experience of which powder types are trouble free and which are most problematic during storage, handling and processing. Each material may be given a processability ranking and this can be correlated with the measured flow properties. Many benefits result from this – batch variability may be investigated methodically and new formulations may be assessed for compatibility with the available processing plant.

In summary matching powder properties and plant is the key to obtaining high productivity and good product quality.

Powders are our business. We sell a universal powder tester that we are intensely proud of, but we’re pragmatists who understand that, for you, it’s all about solving your day-to-day processing problems.

With new customers we look at any process-related issues and normally would measure some samples to tell you what we can discover about your powder. We report on the results and explain how they relate to the way in which the material might behave during processing.

When you’re convinced and purchase an FT4, we follow through with exemplary service during installation, commissioning and training. Regular follow-up and updates ensure that you continue to get the best out of your instrument throughout its lifetime.

Why not start the ball rolling and put us to the test? See what we can tell you about your powder.

Our Experience in your industry

The FT4 system

Flow Additive Studies
Click for More DetailsHow fumed silica flow additive can transform the flow properties of starch

Sampling
Click for More DetailsGuidelines for sampling powders to obtain representative samples for powder testing

Extrusion of cohesive powder
Click for More DetailsHow poor flowing cohesive powders flow better than normally free flowing powders


Powder Flow Properties Measurement using the FT4 Powder RheometerThe FT4 Powder Rheometer was developed to measure the flowability and processability aspects of powders.

The main benefits are to measure and match the characteristics of both materials and processing machinery, so that the consistency and efficiency of powder processing can be improved.

The background to this is described in The Nature of Powders and Processing Powders




 
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