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November 2010

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Subject:
From:
Bob Landman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Bob Landman <[log in to unmask]>
Date:
Fri, 12 Nov 2010 15:12:39 -0500
Content-Type:
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Ha!! Love that show.

Bob

Steve writes:

> Direct communications, should anyone with to negotiate the details of their coating's doom, can go to [log in to unmask] .
> 
> Best
> 
> Steve

Sent from my iPhone

On Nov 12, 2010, at 2:32 PM, [log in to unmask] wrote:

> It really has to be tough working in a technical industry with the name
> Steve Smith, as a Red Green fan the first thing I thought of was duct
> tape...  
> 
> Keep your stick on the ice,
> - Graham
> 
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
> Sent: Friday, November 12, 2010 2:54 PM
> To: [log in to unmask]
> Subject: Re: [TN] UV radiation and conformal coating
> 
> Doug,
> 
> I sent your posting to an old college friend who is a physicist with a
> great deal if working knowledge on chemical finishes as his company
> makes paints and protective coatings for the marine environment.  He is
> teamed with Bill Rollins at Raytheon Tucson on a grant from the MDA to
> develop a whisker-tough conformal coating. 
> 
> He replied:
> 
> Bob,
> 
> Thanks for forwarding this to me.  I am not subscribed to the list, so
> please post this for me.
> 
> All,
> 
> Varnish fails on wood of boats in one or a few years, due to the
> ultraviolet of the sunlight eventually getting thru the varnish [even
> with UV absorbers] and breaking down the cellulose of the wood below.
> Cellulose has a lot of carbon-carbon and carbon-oxygen bonds.
> 
> Indeed; the loss of gloss of varnish is due to surface-oxidation by the
> solar ultraviolet photons breaking the atomic bonds of the
> material at the surface; those surface free radicals react almost
> immediately with atmospheric oxygen, and are literally burned away.
> 
> A carbon-carbon bond has an energy of about 348 kilojoules per mole, and
> will readily break with a barely-ultraviolet photon.
> 
> A carbon-oxygen bond has an energy of about 360 kilojoules per mole, and
> a carbon-hydrogen bond about 413.  For more details, see
> http://www.science.uwaterloo.ca/~cchieh/cact/c120/bondel.html .
> 
> Ultraviolet and even blue-visible photons have enough energy to break
> these bonds.
> 
> Broken atomic bonds create free radicals, and some of these will bond
> onto neighboring polymer chains, causing increased modulus, reduced
> elongation, and in fact the polymer gets smaller. the reason flakes of
> paint curl outwards when they fail is that the outer surface has more
> tensile stress than the material below, due to free-radical damage at
> the sunlight-exposed surface. So, you see, it's going on all the time
> the sun shines.
> 
> Your conformal coating (made of carbon, hydrogen, oxygen and nitrogen
> and perhaps other atoms) is doomed; it's only a matter of time.
> 
> Steve Smith
> Www.smithandcompany.com
> 
> 
> 
> On Nov 11, 2010, at 8:20 AM, Douglas Pauls <[log in to unmask]>
> wrote:
> 
>> Good morning all,
>> 
>> Does anyone know of any papers on the effects of UV light on conformal
> 
>> coating?  Not talking the cosmic radiation hard space kind.  I know it
> 
>> would be wavelength and intensity specific.  Got a question from one
> of 
>> our engineers and I, of course, gave the very intelligent answer of
> "Beats 
>> me".  But I have this wonderful resourse called Technet...............
>> 
>> Doug Pauls
>> 
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