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What kind of super glue / epoxy for Delrin?

RJT

Titanium
Joined
Aug 24, 2006
Location
greensboro,northcarolina
Chipped a corner off a part with a ton of machining on it , and want to mill the edges square and put an inset in it. Can't have any screws (needs to be non conductive) so I'm looking for suggestions on what is the best type of super glue or epoxy to use?
 
A while back as a test I tried common hardware store 2-part 'plastic bonder'. It works well on some plastics but did not work well on acetal. I could flake it off fairly easily. I can only imagine exposure to temperature extremes or fluids would make it worse.

Mechanical fastening seems like the best approach. Either fasteners or an undercut/grooves/knurles that would allow an epoxy or plastic bonder to mechanically retain the repair.
 
The Loctite people seem to have a couple of products for this. They use a primer (Loctite 770 Prism Primer) with their adhesive, 401 Prism.

Do I picture this correctly: you are milling the edge away a square cross-section off the edge, so that when you lay a square rod of replacement Delrin on the edge, it just replaces what you milled away? Would there be a cost-effective way of doing this with dovetails so that you just slide a properly shaped rod into place and the dovetails hold it? Might be worth it, if you want the mend to be invisible.

They make acetal screws, btw.



See here:
https://www.ellsworth.com/globalass...nkel-loctite-design-guide-plastic-bonding.pdf
 
Chipped a corner off a part with a ton of machining on it , and want to mill the edges square and put an inset in it. Can't have any screws (needs to be non conductive) so I'm looking for suggestions on what is the best type of super glue or epoxy to use?
Delrin is a member of a group called low energy plastics. It includes teflon and polypropylene. Neither epoxy nor cyanoacrylate (crazy) glue will stick to them directly. There are super expensive technologies that will work but the most realistic method is available from Loctite. The plastic can be primed with a special primer that is a clear liquid that dries almost instantly. The surface will then accept a number of cyanoacrylates. They are not all the same by any means and are specialized for the surface to be glued. The hardware stuff is often low quality. The primer is Loctite 770. I follow up with Loctite 401 adhesive but there are probably others that would work. If you have a very small job, Loctite also makes a little blister pack consumer kit that you can find at the hardware store. It contains a little bit of the primer on an applicator wick, like a felt tip marker. Then they give you a little bottle of cyanoacrylate glue. The 770 and 401 can get expensive if you don't do a lot of shopping. With difficult gluing problems, I have called Loctite customer support and they are very helpful.

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I don't think I'd trust ANY adhesive for Delrin in the situation you describe. How about a mechanical interlock with the glue just helping? I'm thinking dovetail a piece in and after gluing secure it from sliding with Delrin dowel pins, also glued.
 
I wondered about this, too. Is ultrasonic welding hard to set up for a one-off?
I don't know, its outside my area of experience.

There are several inexpensive plastic welding kits that use heated tools, they have tips that extrude the heated filler into the joint. I've also seen mention of solvent welding on acetal. Both methods are supposedly stronger joints than adhesives.

If it was me, I'd try the heated tool method and do some testing on scrap pieces to get the temps dialed in.
 
Haven't tried it myself but have been told to burn it with a torch and you can get epoxy to stick very well to anything, including polyethylene. You just want to toast the surface layer.
 
I would not try ultrasonics. The parts have to be designed for the process, not the other way around. Even then, it takes a number of parts to zero in on the process.

I would look at mechanical joining with adhesives as mortar.

Tom
 
I have some experience working with Delrin and attempting to glue it. The only way to bond it properly is with plasma treatment which modifies the surface. From memory it changes the polarity of the free radicals to enable adhesion. Similar to how PCBs are treated excepting in that situation you are attempting to prevent adhesion of solder. Probably a simplistic explanation but I'm sure there are forum members that can chime in with a detailed explanation. Personally when I stuffed up with acetyl I used a mechanical system. In my case I made Delrin screws with long heads screw everything in tight with pliers and then machines the protruding heads down to match the surface.
 
Probably not applicable here but it is possible to repair non-glueable stuff using the liquid CA glue/baking soda trick. Best if you can build up a repair over the broken piece.
 
The Loctite people seem to have a couple of products for this. They use a primer (Loctite 770 Prism Primer) with their adhesive, 401 Prism.

Do I picture this correctly: you are milling the edge away a square cross-section off the edge, so that when you lay a square rod of replacement Delrin on the edge, it just replaces what you milled away? Would there be a cost-effective way of doing this with dovetails so that you just slide a properly shaped rod into place and the dovetails hold it? Might be worth it, if you want the mend to be invisible.

They make acetal screws, btw.



See here:
https://www.ellsworth.com/globalass...nkel-loctite-design-guide-plastic-bonding.pdf

^^^^^
on the right track, but place a phone call to Henkel's (Loctite's) engineering group for suggestions. I used an adhesive suggested by them with the 770 prism primer to place a UHMW disc on the end of a punch form cavity. the UHMW disc was certainly retained, we later needed to replace disc from wear and we had to pretty much machine the disc out of the cavity.. we could machine to the steel base, then used acetone to break the bond of the 401 adhesive . Henkel's engineering was of great help. Good luck!
 








 
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