In my professional life, I've dealt with a lot of potting materials. Honestly, they can cause as many problems as they solve, so be careful in choosing one!
The best case scenario seems to be when the potting is used only as a sealant, and not to provide mechanical protection. This allows the use of a relatively soft potting material that flows well, adheres to the board and components, and has a low thermal coefficient of expansion. The expansion when it gets cold or hot is a big issue, because it can crack components or lift IC's off the board.
Using a soft potting requires that a protective housing be used, and that can mean money. Low cost often requires that a minimal housing is used (i.e. a small plastic cup), where the board is placed in the cup and potting is poured around it. This requires that the potting be at least moderately hard, and this increases the risk of damaging circuit components.
Many pottings are pricey, especially for the hobbyist. For my bicycle electronics, I've made do with applying conformal coating (two layers), and then applying "Plasti-dip" over that, as a simple protective layer.
For info on proper industrial products, here are a few useful links:
http://www.dowcorning.com/default.aspx?bhcp=1
http://www.henkel.com/industrial/br...0000380&redDotUID=8000000380&brand=000000QVES
well, that's a messy link. Henkel bought the Emerson Cuming brand, which made a lot of potting materials. I'm not sure if they still make the stuff or not. The Loctite products do include some potting products, though, so you can follow that link.
http://www.masterbond.com/
a supplier of a wide range of potting and encapsulants.
http://www.plastidip.com/home_solutions/Plasti_Dip
not an industrial product, but actually available at hardware stores, etc. The shelf life is extended by storing at cold temperatures, as well as by sealing it with a metal lid instead of the plastic cap that is provided. I use aluminim foil, which minimizes the loss of the solvent.
regards,
Steve K.
