Powders are bulk materials, made from:
• Solids (the particles)
• Liquid (water on the surface of the particle, in the particle or in the air between particles)
• Gas (normally air, between particles or fibrous materials, can also be absorbed by particle however!)
How these three phases interact determines their behaviour thus making powders extremely complex materials
• Powders (particles, gases & liquids) and Particles(solid particles) are two fully separate entities, one being a bulk assembly of 3 phases the latter being a collection of solids
• Much scientific debate has been ongoing about how to best characterize materials.
• Particle characterization allows for the determination of a large amount of specific detailed information about the particles and their properties e.g. Specific gas absorption of particles, surface texture etc
• Powder characterization allows for the behavioural analysis of the bulk assembly E.g. Flow properties, compressibility etc
• Obviously these sciences overlap since particle characteristics do contribute to powder behaviour. But particle characterization alone is not enough nor is it a good scientific approach to predicting bulk assembly/ powder behaviour
- Particle Size & Distribution
- Surface Texture
- Surface Area
- Potential for electrostatic charge
- Hardness / Friability
- Amorphous content
All of these detailed particle characteristics contribute to powder behaviour.
Powder Behaviour = fn (particle characteristics) + fn (environmental factors like humidity and aeration of the powder) + fn (material of production equipment used) + fn (packing state of powder, consolidated, loose, fluid like) + fn (MANY MORE FACTORS)....
This is why at PMC4U we look at the bulk assembly when predicting powder behaviour in specific environments or circumstances.
Important things to recognize:
- Particle properties do not always influence powder behaviour or only part influence behaviour; a powder is a bulk assembly that as a whole also is prone to different stress regimes that influence the packing state.
- Your material is exposed to many different stress regimes during your processes
- Gaining predictive insights into behaviour of your material during specific processes allows for more lean management of the whole process and thus cost reductions overall
- If your material does not behave as required under specific conditions this may influence your final product