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From: Tony Williams
Subject: Re: Side effects of potting compound !
Date: Sun, 03 Nov 2002 08:58:13 +0000 (GMT)
NNTP-Posting-Date: Sun, 3 Nov 2002 08:57:38 +0000 (UTC)
User-Agent: Pluto/1.14i (RISC-OS/3.60)
In article ,
Bob Wilson wrote:
> This may be somewhat pointless. Silicone is completely incompressible.
> While it may SEEM soft and rubbery to the touch, this is only because
> it DISPLACES when you compress one part of it. While this may be great
> for locally applied pressure when unpotted, once it is entirely
> encapsulated by a rock-hard potting compound, there is nowhere for the
> material to displace when presure is applied. Thus, once potted,
> silicone is effectively as hard as a rock.
You've mentioned this before Bob, and of course you are
right. But the fact does remain that pre-encapsulating
delicate components in silicone rubber does work. So
there must be something else going on in there. Maybe
there is enough air inside some comps to allow a
compression of the silicone.
I suspect more than that though.... raw epoxy will have
solidly adhered to components before the shrinkage takes
place, so will be capable of pushing (pulling?) directly
on the comp. The same will happen with any pre-coat that
adheres well. But silicone rubber does not adhere well,
so has no grip on the component.
Note; I still don't know whether the shrinkage in the
epoxy puts a pressure or a vacuum on a component. Gut
instinct still says the latter..... which would further
strengthen the adherance/non-adherence theory.
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