Reversion of PU coatings was a serious issue during the VietNam conflict.
Brian
joyce wrote:
> Being said all the good thing about silicone, I believe few years ago,
> there is a dissociation of silicone (reverse polymerization) under some
> specific solvent/RH related condition (oil based, If I remember
> correctly). As long as someone fully understand the application, you
> will select a good coating for environmental protection. Otherwise,
> there is no "one coating fits all" stuff... May be some grad student
> should start a PhD thesis on that...
>
> jk
>
>
>>-----Original Message-----
>>From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
>>Sent: Monday, September 08, 2003 10:31 AM
>>To: [log in to unmask]
>>Subject: Re: [TN] Silicone conformal coating
>>
>>
>>Of course silicone will repel liquid water, but we are talking
>>here of water in a gaseous phase and my experience is that it
>>passes small molecules, such as water, like a sieve. In the
>>former case, it is a question of the high surface tension of
>>water, but single molecules, ata a time, have no surface,
>>therefore no surface tension.
>>
>>Brian
>>
>>Misner, Bruce wrote:
>>
>>>Brian,
>>>
>>>This diaphram experiment does not take into account the surface
>>>wettability of Silicone which is supposed to be one of its major
>>>protective features (according to Dow) which precludes surface
>>>droplets from forming. Comments?
>>>
>>>Thanks,
>>>Bruce Misner
>>>
>>> -----Original Message-----
>>> From: Steve Gregory [mailto:[log in to unmask]]
>>> Sent: Monday, September 08, 2003 8:54 AM
>>> To: [log in to unmask]
>>> Subject: Re: [TN] Silicone conformal coating
>>>
>>> In a message dated 09/05/2003 2:03:30 AM Central Daylight Time,
>>> [log in to unmask] writes:
>>>
>>>
>>>
>>>> I thought I had reported the details of this in
>>>> my book, but could not find them today. Must have been
>>>
>>somewhere
>>
>>>>else.
>>>
>>>
>>>
>>> Hi Brian!
>>>
>>> It is in your book, on page 329, at the bottom of the
>>
>>section where
>>
>>> you talk about Silicone Elastomers.
>>>
>>> In your book you state that you made a diaphram of
>>
>>silicone that was
>>
>>> 5mm thick, and 100mm in diameter. On one side the air
>>
>>was held at 40
>>
>>> degrees C., and 95% RH, the other side at 5% RH. There was 1g of
>>> water vapor per day allowed to pass through the silicone
>>
>>diaphram.
>>
>>> You stated that is 40 times worse than epoxies, and 20
>>
>>times worse
>>
>>> than polyurethanes.
>>>
>>> Do you have any idea about arcylics?
>>>
>>> Regards,
>>>
>>> -Steve Gregory-
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