Barrier Coatings/In Mold Coatings

Found this stuff....

http://www.smooth-on.com/Release-Agents-and/c9_1123/index.html

Many thanks, but it is a release agent that makes it harder to coat over the casting, as well it does not give a color other than the urethane color it self.

I would really like a barrier coating that will not stick to the silicone RTV mold thus the urethane sticks to this coating. This gives the release and a primary color to the casting.

Have you tried molding without a release agent?

Any liquid you apply to silicone will bead up, and not cover the surface completely.

Nothing sticks to it.

Silicone molds don't normally require a mold release.

Spray on teflon will help, but it's white.

Hi lyn, thanks but polyurethane and polyesters will after a few castings cause the silicone mould to absorb chemicals from the the casting resins and then the casting to stick to the silicone mold.

It is a coating that I am searching for that becomes the surface of the casting, as well, if the right product will act as a barrier between the casting resin and the silicone mold.

Perhaps it is too much of an ask. But I had such a coating 40 years ago.

There must be a coating that:- is kind to the silicone mold, allows the urethane to bond to it, takes up the fine detail, colored to a base wood color, brush able preferable to get into the difficult detail, will cure / dry quickly, needs to be of some solvent base to allow this coating to cover the silicone mold with out beading up, thick enough or elastic enough not to crack when the foam is expanding. Yes a big ask?

Col

Talk to your urethane supplier( I used to buy from BASF). Self skinning urethane is what was used in the early moulded auto dash pads and bumper strips above the instrument cluster. The colouring is mixed into the urethane resin, then the blended A and B is injected (or poured) into the mould. The mould is closed and rotated so as to coat the surface of the mould, in the same manner as in rotomoulding. Timing, temperature and humidity are, as always in moulding urethane, critical. The better the control of those three variables, the more consistent the outcome. The result, as with auto dashboards is a coloured, textured skin(from the mould surface) and foamed core. Of course in auto use the core is slightly flexible, but that is a function of the urethane blend. Or you could buy a Puromat Urethane Injection machine which maintains all three variables within the machine. Last one I bought was just over $200k. Smile…

Many thanks LaserWarrior,

Alas i have asked the suppliers but to no avail so far.

I am using a self skinning foam but using silicone moulds.

I think the dash pad and bumper strips are cast into metal moulds.

Would be great to have such a machine but if I had the $200K I would give up on this working stuff.

I appreciate your help best wishes,

Col