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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