Jim
I know this is a late posting, because I have only just come back on-line
however, what you have encountered is reversion.
The UR materials tend to discolour when exposed to high temperatures, but
this does not generally affect their subsequent performance - if anything it
might improve it because you have ensured a full x-link of the polymer -
fully reacted.
The discoloration may however, be an unacceptable visual condition to your
customer, depending upon their inspection criteria.
Whatever, it will be possible to remove and re-coat if you desire.
You mention that this is a space application, therefore this material will
probably have excellent outgassing characteristics and I can only think of 1
or 2 UR space (NASA / ESA) approved coatings. I am surprised that you have
this reversion, what did their technical staff advise? I would like to know
for my own record.
Regards Graham Naisbitt
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Concoat Limited
Alasan House, Albany Park
Camberley GU16 7PH - UK
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> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of David Douthit
> Sent: 29 January 2002 00:49
> To: [log in to unmask]
> Subject: Re: [TN] Conformal Coating
>
>
> Jim,
>
> You have chemically altered the polymer. It will no longer
> perform it's designed function.
>
> David A. Douthit
> Manager
> LoCan LLC
>
> "Marsico, James" wrote:
>
> > Help! Emergency!
> >
> > We have a completed assembly (top assembly with many boards,
> hybrids, etc.)
> > ready for shipment to our customer (space product). The last
> operation was
> > to ink mark a S/N. The ink is cured at 150 F for 2 hours. The
> assembly was
> > put in an oven at 150 C for two hours. After hours of
> reviewing all of the
> > materials and bill of material, component by component (component data,
> > supplier phone calls, etc.), the only item that is not rated
> for 150 C is
> > the polyurethane conformal coating, which turned yellow/brown
> in color. Can
> > anyone explain what actually happened to the coating and if it
> can be used
> > as is?
> >
> > Thanks,
> >
> > Jim Marsico
> > Senior Engineer
> > Production Engineering
> > EDO Electronics Systems Group
> > [log in to unmask] <mailto:[log in to unmask]>
> > 631-595-5879
> >
> >
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