TECHNET Archives

November 2010

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
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 13:54:03 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (77 lines)
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
> 
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please contact helpdesk at x2960 or [log in to unmask] 
> ______________________________________________________________________
> 
> ---------------------------------------------------
> Technet Mail List provided as a service by IPC using LISTSERV 15.0
> To unsubscribe, send a message to [log in to unmask] with following text in
> the BODY (NOT the subject field): SIGNOFF Technet
> To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
> To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
> Search the archives of previous posts at: http://listserv.ipc.org/archives
> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
> -----------------------------------------------------
> 

______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------

ATOM RSS1 RSS2