hi,

i think solithane 113 is a polyurethane not a silicone.  it is essentialy a
100% solids coating.

phil crepeau

-----Original Message-----
From: Graham Naisbitt [mailto:[log in to unmask]]
Sent: Friday, August 13, 1999 4:04 AM
To: [log in to unmask]
Subject: Re: [TN] Uralane 5750


Pat,

I will give it my best shot and please forgive me if I state the obvious to
you:

Firstly many, but not all, space applications demand coating materials (I
only refer to coating) to have low or zero outgassing characteristics. This
should not be confused with degassing.

Outgassing can lead to the cover of "plasticisers" or other liberated
"nasties" onto delicate surfaces like lenses etc., much less into the lungs
of spacemen!

Uralane 5750 is a polyurethane developed to yield low / zero outgassing.
HumiSeal had something similar called 2B74. However, Uralane does take
forever to cure hence your problem.

In my experience, the coating work is done in Clean-room conditions so the
problem you describe should not occur.

If you don't have clean room conditions, then perhaps the product you are
making does not require to conform to this NASA spec.?

I know for a fact that HumiSeal 1B31 is on many spacecraft.

However, I cannot otherwise see how you can easily avoid the problem you
describe with the coating you are using.

An alternative material suggestion would be to try Solithane 113 which is a
silicone or maybe HumiSeal's new solventless coatings such as 1C61 / 1C63.
They might pass the test? They cure really fast and have MIL Spec
qualification. I am unaware of anyone doing the outgassing test on these,
but they might be interesting.

Otherwise refer to the published NASA list of approved coatings and pick one
that will offer a faster cure.

Hope this helps

Regards,
Graham Naisbitt

[log in to unmask]

WEB: http://www.concoat.co.uk

CONCOAT Ltd
Alasan House, Albany Park
CAMBERLEY GU15 2PL UK

Tel: +44 (0) 1276 691100  Fax: +44 (0) 1276 691227
----- Original Message -----
From: Pat Lujan <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, August 12, 1999 6:10 PM
Subject: [TN] Uralane 5750


> I need help with a problem I have been fighting for 6 months.  We
currently use Uralane 5750 on hi-rel PWA's used in space applications.  Our
method of applying is the brush method per NHB5300.4(3J) April 85.
>
> The quality requirements state that "Coating shall be free from
contamination or foreign material.  Any contaminant visible under 4- to 10-
power magnification shall be cause for rejection."
>
> My problem seems to be the properties of Uralane 5750.  It seems to remain
tacky after it is cured and this appears to attract all airborne particles.
Our CSI and GSI inspectors naturally crank up the scopes to 10 power.   I
used Humiseal 1B31 in the same environment and do not have the same
problems.
>
> My main customers Boeing and TRW have both issued CAR's against this
process as it realates to contamination.  I am in need of any input that may
help me improve my process.  I am a NASA certified Instructor in Conformal
Coating and Staking and have not been able to solve this problem.
>
> Any information that would aid me in continuing my career would be greatly
appreciated.
>
> Pat Lujan
> Senior Mfg. Eng.
> BFGoodrich Data Systems Div.
> Albuquerque New Mexico   USA
> 505.938.5373
>
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