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Silicone Thin Coating?

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Helepolis

Helepolis

Mechanical
Joined
Dec 13, 2015
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212
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Hi all,

Hope the wisdom of the masses will help.

A bit of backround story, so my question will make sense.

We are running, in-vitro, deposition experiments on a human airway model (generic replica).
IMG_20180801_141751_resized_20180801_021820203_upoxcp.jpg

The model is made out of optical silicone

I'm looking for a way to coat the airway model (the inner walls) with a thin layer of silicone or any other kind of flexible and transparent material that can be flattened afterwards, so that the test sample (the coating) can be placed on a microscope slide (for quantification of the deposition).
The model itself will be sliced in half along the plane that is parallel to the broad face, so i'll get two halves of the airways, that way the coating part should be easier (access wise).

We have tried to coat the model with the same material (with a first layer of mold release agent) and we had partial success, as we managed to peel the new layer of silicone of but it wasn't a uniform coat (it pooled to the bottom before it cured.

So basically i'm looking for any plausible ideas on how to coat the airway.
 
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What about multiple coatings. Coating 1 is a catalyst/initiator. Coating 2 is the monomer(s). Then you may get more uniform polymerisation.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.
 
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Perhaps using a very low viscosity material and building it up with a few coats.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
 
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@Latexman, thanks for the suggestion, but i'm not sure it'll work for two main reasons.
The two parts should be thoroughly pre-mixed, otherwise the silicone wont cure properly (but this is easy checked with a test or two).
The more prominent problem is that the channels (airways) are concave, so the silicone pools at the bottom before it has time to cure.
 
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@EdStainless,
can you give an example?
This is the thing that i can't seem to find a solution for now.
 
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You can rotate or tumble the part until the silicone cures.

Silicone itself is a good release agent, even for silicone, but it must be fully cured to prevent adhesion. This usually requires a postcure at 350F for a hour or more.

RTV (room temperature vulcanizing) silicone dissolves well in naphtha (a paint thinner) and makes for a good soft, silicone paint. You can control the paint viscosity, and thus the deposit thickness, by solvent concentration. The non-sagging RTV contains fumed silica, which, after drying the solvent, will prevent the pooling problem you are facing. RTV cures by reaction with moisture in the air, so thin films cure quickly but thick layers take a very long time.

Dip your mold in solution, drain out the excess coating, dry with a blow dryer for several minutes while rotating the mold in your hands to prevent pooling, then let cure for a couple hours in front of a fan.

Many other paints would also work in a similar way.
 
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