Can silicone lubricant from a syringe effect epoxy properties?

Hi all,
I'm using a two part epoxy (Hysol Ea9303na) to bond BK7 glass to titanium with a 50C 12hour cure.
Sometimes I'm seeing debonding occuring under high tensile stress on
the glass bond side. Other times with most variables (bond thickness, adherend cleanliness, surface preparation, mix ratio etc.) well controlled the bonds withstand much higher stress without degradation.
It occured to me today that we dispense one part of the epoxy using a syringe which appears to have a residue on the plunger straight out of the packet. I assume that this is silicone lubricant.
Can anyone offer any experience, anecdotal or otherwise as to the potential effects on epoxy bonds of incorporating this silicone into the mix?
I typically mix about 3g of adhesive in a batch so the silicone level could be significant.
Many thanks,
Carl.
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Carl wrote:

I know that silicone mold-release agents used to make the syringes for dispensing epoxy adhesives for attaching disk heads to the actuator in hard disk drives have played havoc by disturbing the head-disk interface, which is an incredibly engineered interface that is completely intolerant of silicone. Even so-called "silicone free" syringes have been known to cause problems, due to cross-contamination of the silicone from neighboring production lines.
That was years ago -- the disk head adhesives used today are definitely silicone free. Using one of them might solve your problem, but the cost might be prohibitive. These adhesives are very expensive.
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<snip> .......................the disk head adhesives used

Thanks. The epoxy isn't actually supplied in the syringes, it's something we do to meter it out of its container. So I can theoretically use another method.
Carl.
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absolutely! consider all the failures are consistent with poor adhesion the critical interface is the surface that to which the epoxy is to bond with as well the epoxy "surface" any plasticizer present in the plastic u r using such as the syringe will adversly effect bonding most likely if u r seeing something in the syringe its mixing or is soluble in the epoxy I would b happy to help u more email me
www.entropyltd.net
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try cleaning the syringe with acetone etc

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i would also be careful as to what u use to mix the epoxy
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<snip>

I_keep_trying,
Thanks for your input, I'll keep the discussion in the group for now.
I am running a trial now with epoxy that has not come into contact with the syringe. Also, we mix the two epoxy components inside a food grade ziplock plastic bag using a roller, mainly to exclude air. It seems to work very well.
I'm still grateful for anyone's experience with this.
Cheers, Carl.
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Just for the archive..
I have run a trial bond without using a syringe. So far the bond is stronger than before with no degradation visible under increased load.
This is very encouraging.
C.
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<snip>
Also, we mix the two epoxy components inside a food

Just a word of warning, Ziploc and similar plastic zipper lock bags usually have residual silicone on them from their manufacturing process. If you know that the silicone is a problem then you might want to stay away form the bags as well.
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On 22 Jan, 16:32, mr snipped-for-privacy@hotmail.com wrote:

Thank you. I really appreciate your advice.
I had thought that this could be an issue so I am now in contact with a company who will supply us with our two parts of epoxy pre measured in "hinge packs". These are those plastic bags with a clip that divides the two components that is removed to enable mixing. We had seen significant variation in adhesive properties (measured with a durometer on cured samples) that were partly due to variations in mix ratio - even though we are using 0.01g resolution scales to measure the components. Anyway, the upshot of this is that all the materials supplied to us from this company are certified silicone free.
Thanks everyone.
Carl.
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Carl wrote:

Are you sure the variation isn't due to thoroughness of mixing? A/B formulations are often colored with carbon black and TiO2 to make one part black and the other part white. That way, you can tell when they're thoroughly mixed because the mixture will be a uniform gray.
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Hi Mark,
The components are red (very low viscosity) and beige (very high viscosity). We mix for at least 5 minutes and always use the same process. As you say, it's quite easy to see streaks in the mixture if not completely mixed. I have my suspicions that our scales, although calibrated have some inaccuracy right at this end of the scale that is making our mix ratio fluctuate.
Cheers, Carl.

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