Delrin adhesive type.

[Steve GParticipant @steveg24616]

Hi,

I am wondering which adhesive to use for delrin plastic. I need to glue an anchor nut inside a delrin tube and wondered whether cured fibreglass resin would be adequate. Any ideas?

Many thanks.

Steve

[Steve GParticipant @steveg24616]

[Jeff DaymanParticipant @jeffdayman43397]

I'm sure there will be others who disagree, as usual, on forums, but in my experience in industry and home shop for over 30 years in plastics there is no glue that will stick to acetal resin, Delrin being one brand of acetal. I suggest you devise a mechanical rod or bar with the nut in it, and either jam it in the acetal tube or screw into it from outside with a small hole through the tube.

Polyethylene (and variants of it) Polypropylene and PTFE are also extremely difficult to glue. The styrenics like polystyrene, ABS, and PC/ABS blends glue very well. Polycarbonate, rigid urethanes and rigid polyester also glue well.

[SteviegtrParticipant @steviegtr]

I agree. I use a lot of Delrin /Acetal. It is not the sort of thing anything wants to stick to. Very sort of greasy if that is the word. The only thing I could suggest is to put a shoulder inside for the nut to sit against, if possible.

If you could find a solvent that attacked the Delrin then maybe find a glue that is based on that. Like solvent pvc pipe glue that actually melts the plastic pipe together.

Good luck.

Steve.

[Adam MaraParticipant @adammara]

A foam based VHB tape might do the job, I use them to bond acrylics. I have also found Wilko's Hard Plastic adhesive to be pretty good some. But as the others have warned, many 'oily' plastics are difficult to glue, I opt for 'mechanical' fixing in preference.

[Ron LadenParticipant @ronladen17547]

I have not actually tried it but I looked into seeing if there is an adhesive for glueing delrin some time back and I read somewhere that Loctite 411 gap filling cyno will stick to it. If I remember I think it needs to be used with a Loctite primer but which one I dont know.

I never tried it so dont take my word for it you would need look into it further but its something I read when looking at the time.

Edited By Ron Laden on 28/04/2020 20:44:42

[John PParticipant @johnp77052]

Posted By Ron Laden

I think it needs to be used with a Loctite primer but which one I dont know.

Ron

Look in RS Components Loctite 770 RS Pt no 108-722

suitable for Polyethylene (and variants of it) Polypropylene and PTFE.

John

Edited By John Pace on 28/04/2020 20:59:42

Edited By John Pace on 28/04/2020 21:11:30

[Steve GParticipant @steveg24616]

Great info.

Thanks for the replies, this confirms my thoughts regarding the success of anything adhereing to Delrin reliably. I think I will have to devise a mechanical support for the nut to attach to.

The application is within a high power antenna balun assembly thus not being able to use a metal support structure. I will have to figure something out.

Thanks again, your support has been valuable.

Steve

[John Paton 1Participant @johnpaton1]

I have used the 'special' primer on PTFE with superglue. I t worked but I had almost zero confidence in the strength and probable life of the joint. (I managed to peel off some 'test pieces' without too much effort.)

I am guessing that it demands a very specific surface texture ('micro texture'?) to achieve the bond strength claimed. My understanding is that the primer chemically etches the surface of the plastic.

[John Paton 1Participant @johnpaton1]

I have used the 'special' primer on PTFE with superglue. I t worked but I had almost zero confidence in the strength and probable life of the joint. (I managed to peel off some 'test pieces' without too much effort.)

I am guessing that it demands a very specific surface texture ('micro texture'?) to achieve the bond strength claimed. My understanding is that the primer chemically etches the surface of the plastic.

[duncan webster 1Participant @duncanwebster1]

Can you thread the inside of the tube then make up an insert?

[Bill PudneyParticipant @billpudney37759]

Some time ago, I wanted to glue some al. alloy bits to some delrin bits. So I asked the Tech Department of the material manufacturer what to do. They said (paraphrasing here), ….. "….Delrin (acetal resin) is very difficult to glue using any adhesive, the best thing to achieve a moderate joint is to design the joint so that there is some mechanical load taking system, e.g. a thread, and not rely on the adhesive to provide any strength to the joint. Slow cure (24 hour epoxy) will provide the best solution, clean scrupulously, clean again, mix and apply epoxy EXACTLY i.a.w. instructions and assemble. Allow to cure in a warm place for at least 24 hours before handling. Then don't be surprised if it falls apart!!

I used to use delrin as a mould for carbon/epoxy parts with only the minimal parting agent.

cheers

Bill

[Clive FosterParticipant @clivefoster55965]

If you can get the surface really clean with no contamination the Pattex branded plastic primer and super glue adhesive occasionally sold by LiDL will produce a moderate strength bond on Delrin. Sort of level you associate with ordinary sellotape I guess.

As ever with adhesives peel strength is the difficult bit.

Not enough, and less than trustworthy, on its own but if you have reasonable contact area and can't get decently strong mechanical fastenings in it will add useful extra strength.

I'm a fan of screw and glue joints with screws at each end to prevent peel (and maybe in a couple of other places for long joints) with a decent glue area supplying most of the strength. Especially useful when the easy way is to build up onto fabricated sub assembly parts rather than make a pile of precision components for assembly.

Clive

[KWILParticipant @kwil]

http://reltekllc.com/adhesivesfordelrin.aspx ?

I have used Bondloc DTB adhesive on delrin assemblies, some included a metal component, trying to simulate a previously metal/delrin moulding, so far so good but under light load.

Edited By KWIL on 29/04/2020 09:26:14

[JourneymanParticipant @journeyman]

Would it be possible to press the nut in hot? Delrin melts at quite a low temperature and hot forming is used to make leadscrew nuts which are then a perfect fit for the screw. It depends rather as to whether the delrin tube is pre-existing or can be manufactured. With a hole smaller than the nut, the nut could be heated and pressed in forming an exact mechanical match. To stop the nut exiting a slightly larger disc could be heated to deform more plastic over the top of the nut. It may even be possible to make the nut/delrin as an insert and heat or friction weld it into the tube.

John

Edit: Add link

Edited By Journeyman on 29/04/2020 09:39:59

[Steve GParticipant @steveg24616]

Thanks for the replies, great reading. I think I have a workable solution.

Based on the last few replies, my solution will be to make an internal ring with an OD that fits the ID of the tube and there is sufficient room to accommodate the nuts (two off at 180 degrees) and about three times it's thickness.

As mentioned by John, I shall drill through the internal ring and then cut to the depth of the nuts a minor diameter, just below the across flats but smaller than the major diameter of the nut. By applying a minimum of heat to prevent too much deformation, press in the nuts.

The nuts will be held captive and providing both nuts are not removed simultaneously, should remain inline and serve in a pseudo anchor nut fashion. The nuts will not need to support a high torque, just a nip up, or slightly snug, as they say.

Great support guys, I managed not to scratch all of my hair out on this one.

Now I wonder, as it's black Delrin, can I weld it using black tie wraps as welding sticks? Haha, I will experiment this and report back sometime later.

Steve

[Jeff DaymanParticipant @jeffdayman43397]

If you have acetal cable ties, they may be usable as filler rod for hot air welding of acetal. Many cable ties though are nylon. It may appear to bond to acetal with a hot air welder but the bond will be weak. May have better results sawing off some acetal sticks from a block and using those if welding acetal. Do be aware that acetal outgasses some very toxic stuff when heated – outdoors and with wind blowing the gases away from you would be a good idea.

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