What kind of super glue / epoxy for Delrin?
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    Default What kind of super glue / epoxy for Delrin?

    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?

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    Bonding Delrin / acetal is tricky, but there are ways like ADHESIVES for DELRIN and ACETAL & Bonding Acetal | Industrial Adhesives| Bond Plastics - Permabond

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    Gluing acetal doesn't work in my (limited) experience. Why not use a non-conductive fastener?

    Find Plastic Screws products and many other industrial components | MISUMI USA

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    Sami,
    Both your links have huge minimums, going to try some 2 part epoxy for plastics, or go with plastic screws.

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    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.

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    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/globalasse...ic-bonding.pdf

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    Quote Originally Posted by RJT View Post
    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.

    Sent from my SM-G900V using Tapatalk

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    I didn't think anything would bond acetal but apparently this does: http://reltekllc.com/Portals/0/PDF%2...ONDiT_B-45.pdf

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    Don't know the application, but might consider plastic welding...

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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.

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    Quote Originally Posted by jancollc View Post
    Don't know the application, but might consider plastic welding...
    I wondered about this, too. Is ultrasonic welding hard to set up for a one-off?

    Also, apparently Permabond has a primer/cyanoacrylate pair that's recommended for acetal: Permabond POP Primer and Permabond 731 , and they also say that a heat-cure epoxy works. They recommend their Permabond ES5741

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    Quote Originally Posted by bosleyjr View Post
    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.

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    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.

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    Bondit makes a glue for Acetal/ Delrin. I haven't used it myself but have seen it used.
    mike

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    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


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