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Fiberglass/epxoy bonding issue

My company has recently been forced into an alternative epoxy solution, and it does not like to bond to the bonding agent previously used. The part we have the most problems out of bonding to is a cylindrical steel tubing. This tubing is flashed with copper then followed by an tin plating which our customer requires. The tubing has a tab welded to it, is grooved and then the bonding surface (external) is sandblasted to "try" to optimize adhesion.
After the tube is wound, baked, and finished, it is tested a mass spectrometer at 10-7. We are currently down to a leak rate of around 8%; however, we know our bond isn't what it should be due to the fact if the tube is thermocycled (-40 °F - 300 °F over a 24hr period) we lose another. 8-10%. Our return rate is dropping, but I wanted to know of any suggestions. We have tried 6 different bonding agents to date which were "recommended" with only 1 decent result which is what we are using currently.
No filler is being used in the resin system.

Any suggestions?

David Southerland
- Greenville, Tennessee, US
2007

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2007

Freeman Newton [deceased]
(It is our sad duty to advise that Freeman passed away
April 21, 2012. R.I.P. old friend).

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2007

Thanks for your input. We tried hydrated alumina with no success; however, we may have had to small of a micron for proper absorption. In order to facilitate proper wet out of the fiberglass strands, the resin has to be at a certain viscosity. The desired viscosity creates non suspension of the filler.
We are currently doing a study on Alodine vs. Anodized plating on the flange; however, we are at a stand still with the tin plating on the center contact.

Thanks,
David

David Southerland [returning]
- Greeneville, Tennessee, US