Although not familiar with the Insulcast material, based on the
nomenclature I guessing its an "Addition Curing Silicone". If this is
the case there is a long list of "inhibitors" that will give you
problems including: Latex, Neoprene, Buna W Rubber, Natural Rubber,
Certain Tapes etc.
For a more complete list go to the Emerson & Cuming web site and look
under "technical tips".
Bill C.
-----Original Message-----
From: Carl VanWormer [mailto:[log in to unmask]]
Sent: Friday, July 06, 2001 9:41 AM
To: [log in to unmask]
Subject: [TN] Insulcast RTVS curing problem (caused by latex gloves)
We are potting an automotive application using Insulcast RTVS 27
(thermally
conductive potting compound) using room temperature curing. An autopsy
of a
failed unit showed areas of gooey (uncured?) compound around several
components of the assembly. The gooey areas are up to 3mm deep, and
will
flow slightly with gravity .
This particular assembly had been re-worked before (un-potted, fixed,
then
re-potted). The areas that were gooey were not the re-worked areas, but
were areas where the old potting material had been removed. There has
also
been a similar gooey effect around a Nitrile gasket.
The vendor suggests that latex gloves (worn during the handling/potting
operations) can cause the platinum based catalyst to become ineffective.
A
different compound with a tin catalyst (about twice the cost) will
eliminate
the latex sensitivity. We have been told to eliminate the latex if we
are
going to stay with the existing compound.
We have also been told that Nitrile can cause similar results, but by
using
higher temperature curing (oven), the potting compound should cure
before
the Nitrile can cause a problem.
Has anyone else had similar experiences with this compound?
How about any better solutions?
Carl Van Wormer
Cipher Systems
1815 NW 169th Place, Suite 5010
Beaverton, OR 97006
Phone (503)-617-7447 Fax (503)-617-6550
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