From: rpreed@comcast.net
Sent: Monday, November 01, 2004 10:06 AM
To: Michael R. Kalish
Subject: Re: copper primer (fwd)

Mike,
Here's Dave's message. Please reply to me if you need more information.
Dick Reed
 

	-------------- Forwarded Message: -------------- 
	From: "David Evans" <davevans@rmplc.co.uk> 
	To: "Dick R" <rpreed@comcast.net> 
	Subject: Re: copper primer 
	Date: Sun, 31 Oct 2004 20:31:46 +0000 
	
	Hi Dick,
	We did do some bond tests many years ago with various primers - but that was in the days before we understood the vagaries and difficulties of tensile butt joint testing (and shear testing). About the only conclusion was that almost anything was better than untreated copper.
	In later days, we put a lot of time and trouble into designing and testing the valve head specimen and I really believe that Princeton will be wasting their money if they just have CTD make a simple butt joint and test it. 
	I didn't know DZ 80 was being discontinued but I do know that it consists of a phenolic resin varnish blended with an alcoholic solution of nylon. 
	The a phenolic resin varnish alone is pretty effective - I know this because DZ80 is not stable indefinitely and the nylon tends to come out of solution. With the crude tension and shear test we did, there was not a measurable difference between the two.
	Another treatment which I have used is a proprietary copper blackening process. This turns the copper surface black because an oxide (Cu(sub2) O) is formed and this oxide sticks very well to the copper - unlike the more usual copper oxide (CuO) which doesn't stick at all.
	The disadvantage of both the phenolic resin varnish and the 'blackening; process is that the former has to be cured at something around 120 C (after drying at RT but so would any primer to be used with a hot curing bonding resin) and the latter has to be done by immersing the component in a near boiling water solution of some sodium salts. The name that comes to mind for this process is 'Ebonol' maybe you could find some details on the web if not and you are interested in it, let me know - I'm sure I can turn something up. The black oxide is an electrical insulator but the coating applied is so thin, it couldn't be relied upon.
	When a copper surface has been cleaned and prepared for bonding, it oxidises very quickly to form copper oxide (CuO) on the surface and this doesn't stick very well to the copper substrate. So when you bond you are bonding to a loose friable layer of copper oxide. The major advantage gained from a primer is that the copper can be coated immediately after cleaning and if it is a large part, it must be cleaned and primed in stages so the primer is applied straight after cleaning. If there is a 'significant' delay (say much over 30 minutes) between cleaning and priming, much of the advantage of priming is probably lost. Since covering the surface to prevent oxidation is the major function, almost any resin could be used as a primer, first dissolving the resin in a solvent to form a low viscosity varnish and then applying this to the copper surface and drying. If the final bonding is to be done with a hot curing resin (such as CTD 101 - let me know i! f you want a similar but better product like the ITER mix but based on Bis A resin and very much cheaper) it is best if the priming resin is also hot cured before final bonding. It is best if the priming resin is dry when the solvent has evaporated. Let me know if you need an outline process / recipe .
	It is easy to waste a lot of money on testing and collecting non-engineering data. Beware!! Nothing is ever straight forward is it.
	
	At the Board meeting in Jacksonville Nishimura and Ogata were elected to the Board, along with a number of others. Ogata was missing from Gubser's list of nominees but I was able to get him added and elected.
	Best Regards,
	
	Dave. E
	

		----- Original Message ----- 
		From: rpreed@comcast.net 
		To: Dave Evans <mailto:davevans@rmplc.co.uk>  
		Sent: Sunday, October 31, 2004 2:41 PM
		Subject: copper primer

		Hi Dave,
		Princeton is having CTD do some tensile(bond) tests with CTD101/glass and a copper surface. We discussed this earlier. Now, the question of a primer for the copper surface has come up. CTD says that DZ80 (made in England, I believe) is being discontinued. They have also tried Chembond (I don't know anything about this agent) and found reasonable comparibility to DZ80. If my memory is accurate, I think that you have tested a series of primers in the past. Any comments on what CTD should use?
		Hope all is well.
		Dick