Coating Efficiency.
This is a bit out of my field, but I would have thought that the electon microscope maker would advise on discretion sensitivity of additives such as trace pigments. Many years ago, Warren Spring laboratories used light detection on the output of a continuous mixer to determine the degree of homogeneity using coloured additives. It would seem that the effectiveness of the coating process is suspect, but it is not clear whether groups of particles are not being coated or if some particles are not coated around their whole surface. I would have thought that a 3D microscope would be quicker and simpler than an electon microscope with UV light. Were the 'mixed results' considered unreliable or perhaps reftecting 'mixed performance'? Sorry OI can't be more helpful. ■
Re: Coating Expanded Perlite
The "mixed results" I would say were more towards mixed performance rather than reliability. Also, the uncertainty there was that we were not sure how well our tracer indicated the degree of silicone coating on the perlite (as in whether our tracer coats the perlite as well as/worse than the actual coating). Anyways thank you for your help, can you suggest any literature I might be able to resort to regarding the quantitative detection of silicone emulsion? ■
Coating Process
Sorry, I can't help with the detection requirements. You obviously have to consider carefully what tracer material to use, but unless there was a selective chemical affinity I would expect the distribution of a fine particle within a liquor to reflect the degree of coating of the liquor.
It would be interesting to know how the coating was applied as it is essentially requires a combination of dispersion and diffusion, presumably some form of tumbling action to maximise surface-to-surface particle contact under light pressure. It is important to be able to quantify the performance, but if the process is not proving satisfactory that also demands examination. ■
Re: Coating Expanded Perlite
is this sorted or you are still looking for solution? ■
Coating Expanded Perlite
Hi Lyn,
I would like to ask a question with regards to coating expanded perlite. We would like our perlite to be coated in-line after expansion such that when it cools, it becomes hydrophobic and does not absorb water. The coating that we currently use is Dow Corning 346 emulsion (which contains polydimethylsiloxane as its active ingredient) diluted with water such that it is roughly 1-2% by weight of the entire mixture.
In order to detect how much of our perlite is actually being coated, we had included tracer oil in our coating mixture for the purpose of being able to visually observe how much perlite was coated under a UV light. However, we have received mixed results with this and would like to attempt a more precise method of detection.
The actual hydrophobicity can be tested simply by placing the perlite in water and observing whether it floats/sinks, but a more direct and quantitative method is needed.
Something else we have attempted is to observe different samples of coated/uncoated perlite under a scanning electron microscope to see if there is any glaring difference between perlite particle surfaces that are coated or uncoated, but this has ultimately been unsuccessful since we do not know what our coating looks like under the microscope, nor do we know whether we can even see this coating under the microscope.
Are there any suggestions you can make about how to increase the visibility of the Dow Corning 346 emulsion coating mixture such that it can be detected under an electron microscope? Thank you. ■