Adhesives losing the battle with lubricants :(

[air_dannon]

Hello All,

This is a small, not quite pen-sized, pneumatic gun that gets filled to 500 psi

I have a barrel sealing piston on this "snipe stick" copper w/ brass pneumatic. The piston is a 3/4" long piece of copper tubing with one end soldered shut with a round piece of copper and then filled nearly full with JB Weld. As the copper soldered end is facing toward the barrel, it needed a rubbery material with a lubricant to get that initial seal going before the pressure does the rest. It works perfectly, but over time a problem has come up. The rubbery materials I have been adhering to the copper have been failing. Some last longer than others, but they eventually detach from the copper end.

I've tried several materials: bike tube rubber, neoprene, and most recently I took the grippy/plastic part that slides onto metal tension clamp handles and used that. The tension clamp material sealed the barrel great and I adhered it the copper end with superglue.

I thought the petroleum lubricants I was using were responsible for degrading the superglue/gorilla glues I've tried, so after some research, I decided to try "plumber's grease" or silicone grease (90% silicone, water-based). I thought this would be slippery and gentler on the bond needed on my piston, but this morning I heard the familiar sound of a piston problem. I opened it up and the rubbery end was detached on my piston again.

Am I wrong to think the non-petroleum, plumber's grease would not mess with the superglue adhesive? I was told the prior used, lithium spray grease could be the culprit in degrading the adhesion...?

Anyway, if you have experience or advice, I'd appreciate it.

Thanks,

Dan

[wyz2285]

What I used to do, embed a piece of rubber into epoxy, keep it in place and stops the rubber piece from expanding duo to use.

[air_dannon]

smart! an anchor is what I need! Thanks!

[jackssmirkingrevenge]

It helps if you use thick rubber too, 1/4" thick will stick better than 1/8".