Boron Nitride Particle Size determination

[Polymat]

Hello

I have cBN in a high viscous polymer. I am looking for a method to measure the particle size of the BN. I have planned to mill the mixture in a roll mill for BN size reduction. I would like to know a best/quick method to determine the BN particle size. Any addtional inputs are welcome...

thanks

 

[CoryPad]

Can you provide an estimate for the expected size of the cBN? Usually these are small, < 1 mm, so that could limit the available options.

There are sieves used for quantifying powder sizes.

Or for truly accurate measurements, you could take some of the particles and view them under a microscope (optical stereomicroscope or Scanning Electron Microscope).

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Demon3]

I am not sure that I understand the system you have. Do you mean CBN in a thermoplastic or in a polymer solution? If you have particles in a polymer melt then it makes determination of the particle size different. For example if you mill pellets of polymer containing filler (CBN) then you will not measure the particle size of the filler but of the filled polymer particles. Depending on the polymer you could burnt it away by heating in air (e.g. 400°C or so) or you could dissolve away the polymer and filter. Then, when you have the CBN particles isolated you can size them by sieving or many other techniques (light scattering, ligh microscopy etc). Or, if they are in a polymer melt you could cut a cross-section and do light or electron microscopy and then particle size analysis). The reason I mention these methods in particular is that I have used them to analyse filler or agglomerate size in polymers so I know they work.

Good luck.

 

[patprimmer]

I generally just dissolve the polymer and run through a sintered glass filter. So long as the particles are not smaller than the sieve it is OK.

You can calculate if you lost material through the sieve by calcs from weight of retained filtrate vs weight expected from the SG of the original compound.

If the particle is so small that you lose filler through the sieve, you will then need the more sophisticated methods.

Regards

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[Compositepro]

The standard test for this is a Hegman Gage. It is a steel plate with groove with a depth that tapers to zero. A sample of paint or other viscous material is placed in the groove and a scraper is swept over it. When the largest particles are the size of the groove depth streaks are seen in the coating.

http://www.precisiongage-tool.com/GrndGage.pdf

 

[patprimmer]

I just smear some of the filtrate onto a microscope slide with a micron scale on it and measure the particle size with the scale.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Polymat]

Thanks Guys...

1. Cubic BN in high viscous theroplastic polymer solution (Dissolved in solvent)
2. I'm little concerned with the hegman gage,the orientation of the particles will have an effect to give wrong results.

Any other methods...

Thanks

 

[Demon3]

If the particles are really cubic then there will be no orientation effects will there?

 

[Compositepro]

How would you define a wrong (or correct) result? Particle size distributions are one of the most difficult things to measure and the measurement method determines the answer. Microscopic visual analysis is the most informative and potentially useful methods but requires great skill on the part of the observer and doesn't produce very quantitative results. It is best for R&D. QC hates microscopic anaysis and wants a method that produces consistent results (don't we all). You have to define what it is you need to know about the particle size distribution. You can measure number average, surface area average, or weight (volume) average particle size, aspect ratios, etc. When someone says the the particle size of a powder sample is "X" without defining anything more, it is a meaningless number and shows a lack of understanding.

 

[unclesyd]

We analyze particle size and distribution of additives in Nylon using one of several Coulter Counters. We generally use the solvent method to remove the polymer. In some cases the same solvent can also transport the particles in the Coulter counter. On the feature additives we use X-Ray Fluoresce to measure the quantity of the additives as Ti, Si, and so on.
There are several different types of particle counters on the market and many labs that can perform the analysis for you.

http://www.beckman.com/products/Discipline/Life_Science_Research/pr_disc_gen_partchar.asp?bhcp=1