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Forum index » Science and Technology » Chem » Coatings
Resistance of epoxies to ozone
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Nicolas DELFAU
science forum beginner


Joined: 27 Jun 2005
Posts: 15

PostPosted: Wed Apr 12, 2006 4:50 pm    Post subject: Resistance of epoxies to ozone Reply with quote

Dear all,

We've got a wide range of 2-component epoxy coatings and I was recently
asked which one is best suitable against ozone. The application is on inox
substrate, which mustn't be of high quality as it already corrodes under
ozone beam.
Does someone has an idea of which chemical family to use ?
Phenol-novolaques, bisphenol A resins or epoxy-vinylester (Derakane
products) ? And what about the hardener ? We use to formulate our own
adducts or hardeners and we've got a wide range of raw materials to help us
get through this.
Any tip ?
Thank you in advance.

Nicolas DELFAU
delfau.nicolas@peintures-sob.fr
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Al1131
science forum beginner


Joined: 01 Mar 2006
Posts: 4

PostPosted: Wed Apr 12, 2006 7:21 pm    Post subject: Re: Resistance of epoxies to ozone Reply with quote

In article <e1jb5d$5lv$1@s1.news.oleane.net>,
"Nicolas DELFAU" <delfau.nicolas@peintures-sob.fr> wrote:

Quote:
Dear all,

We've got a wide range of 2-component epoxy coatings and I was recently
asked which one is best suitable against ozone. The application is on inox
substrate, which mustn't be of high quality as it already corrodes under
ozone beam.
Does someone has an idea of which chemical family to use ?
Phenol-novolaques, bisphenol A resins or epoxy-vinylester (Derakane
products) ? And what about the hardener ? We use to formulate our own
adducts or hardeners and we've got a wide range of raw materials to help us
get through this.
Any tip ?
Thank you in advance.

Nicolas DELFAU
delfau.nicolas@peintures-sob.fr



I have found that highly filled epoxies, that is 70% of so filled with
silica are highly resistant to such vigourous environments as oxygen or
carbon tetraflouride plasmas. My attempt to remove these materals was in
a plamsa etcher.

I had to resort to either fuming nitric or fuming suphuric acids to
remove these materials while depackaging plastic encapsulated integrated
circuits.

Al
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Uncle Al
science forum Guru


Joined: 24 Mar 2005
Posts: 1226

PostPosted: Thu Apr 13, 2006 12:01 am    Post subject: Re: Resistance of epoxies to ozone Reply with quote

Nicolas DELFAU wrote:
Quote:

Dear all,

We've got a wide range of 2-component epoxy coatings and I was recently
asked which one is best suitable against ozone. The application is on inox
substrate, which mustn't be of high quality as it already corrodes under
ozone beam.
Does someone has an idea of which chemical family to use ?
Phenol-novolaques, bisphenol A resins or epoxy-vinylester (Derakane
products) ? And what about the hardener ? We use to formulate our own
adducts or hardeners and we've got a wide range of raw materials to help us
get through this.
Any tip ?

Most epoxies are based on diglycidylated aromatic nuclei. Ozone
cleaves benzene rings as well as all other unsaturated systems. You
are eaten if you are limited to common organics.

One hope is to load the epoxy with inorganic filler to blunt ozone's
attack by physical blockage. Finely dispersed oxides are a good idea
(silica or alumina; fumed silica will tremendously thicken the mix at
low loadings). Metallic aluminum dust or paint flake would be even
more interesting, as would waste silicon dust from semiconductor
sawing. Ozone attack on the filler would give alumina or silica of
greater volume than the elements, swelling the attacked surface into a
protective cap as the organic degraded. That might be clever.

Have you tried something cheap and easy, like dipping a layer of
paraffin wax to block the ozone? Straight paraffin shrinks too much
when it solidfies, but it is easy to compound to render it flexible.
Just be careful that all components are fully saturated aliphatics.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz3.pdf
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Nicolas DELFAU
science forum beginner


Joined: 27 Jun 2005
Posts: 15

PostPosted: Tue May 02, 2006 4:03 pm    Post subject: Re: Resistance of epoxies to ozone Reply with quote

Thank you Al,

In fact, it was a question a customer asked me on an epoxy that has long
been released. I don't intend to reformulate it, I only wanted to have an
idea of its behaviour in such conditions. At first, I thought that the
aromatic ring could be resistant enough, ... but it seems not.
If, one day, we want to create more resistant epoxies, I would probably try
your second solutions, which seems to me a better and easier way.
Anyway, thank you very much for your time.

Regards.

Nicolas DELFAU
Peintures SOB
FRANCE
delfau@wanadoo.fr

Quote:
One hope is to load the epoxy with inorganic filler to blunt ozone's
attack by physical blockage. Finely dispersed oxides are a good idea
(silica or alumina; fumed silica will tremendously thicken the mix at
low loadings). Metallic aluminum dust or paint flake would be even
more interesting, as would waste silicon dust from semiconductor
sawing. Ozone attack on the filler would give alumina or silica of
greater volume than the elements, swelling the attacked surface into a
protective cap as the organic degraded. That might be clever.

Have you tried something cheap and easy, like dipping a layer of
paraffin wax to block the ozone? Straight paraffin shrinks too much
when it solidfies, but it is easy to compound to render it flexible.
Just be careful that all components are fully saturated aliphatics.

--
Uncle Al
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