Permanent Bond of these two items

[Dolphran]

Hello

I want to permanently bond a metal plate to a plastic box. I don't know details of the materials, but I have provided images here that hopefully will give those in the know enough for a good guess.

The box will hang from the mounting plate when used in a stage performance environment. I will try to treat it kindly, but it will unavoidable take some abuse. I would like to bond to be as strong as the plastic box itself. I would use screws, but because of the way the electronics are mounted in the box, this is not practical.

The plate is 5" x 2". The area on top of the box between the two ridges that define the flat top portion is about 6.5".

I have some J-B Kwik Weld, but I figure I have only one shot at this so I had better seek expert opinions first.

 

[Dolphran]

Tring again for the images

 

[Dolphran]

And The second image (hopefully)

 

[CoryPad]

Unfortunately the answer depends heavily on the materials used for these items. From the pictures, I would guess ABS, which means your JB Kwik Weld probably would work fine. Make sure you clean the surfaces prior to bonding, preferably with a fast evaporating solvent like acetone. If the housing is polypropylene (PP), then it will be extremely difficult to get a good bond with any adhesive. Good luck.

 

[Dolphran]

Is there any test I can reasonably do on the plastic case to determine its composition. From what I've read I assume the issue is HSE vs. LSE material. Is there any easy at-home test for determining which I've got?

Is part of the adhesion issue that that same layer of adhesive has to bond to both surfaces? I guess I'm asking if a VHB double sided tape like 3M 5952 would give me a better shot at strong permanent bond?

 

[Dolphran]

There is also 3M 4298 Adhesion Promoter - which I can get in a small amount from Amazon here: Link

Would this help given that I don't know the composition of the plastic? I think the metal plate is powder coated aluminum, but I'm not even 100% sure of that. Would the adhesion promoter help with J-B weld type adhesive or only with the VHB tape? How about J-B Plastic Weld? Would that not work on the metal plate?

 

[berkshire]

I think you will be better off with the VHB tape, if it does fail the failure will be a slow peel. The JB weld failure will be more sudden.
B.E.

You are judged not by what you know, but by what you can do.

 

[MikeHalloran]

Given two rigid adherends, VHB is less likely to fail by slow peel than by short term cleavage. My experience says it _will_ fail, within a year, with no useful warning.

I personally would use VHB, only to provide fixturing while an adhesive like 3M #5200 or an unfilled RTV silicone cures to full strength.



Mike Halloran
Pembroke Pines, FL, USA

 

[MikeHalloran]

And just for fun, I'd run a couple of big-ass ty-raps around the outside of the assembly, and cinch 'em up real nice.



Mike Halloran
Pembroke Pines, FL, USA

 

[CoryPad]

Dolphran,

Are you sure the housing does not have a recycling code on it that identifies the polymer? You can call the manufacturer to ask about the material. There are some do-it-yourself polymer identification tests, but you would need to remove a piece of the housing and the tests are destructive.

You are correct that surface energy is an important factor. The adhesion promoter would be helpful for either the bulk JB epoxy or the tape adhesives assuming the plastic housing has low surface energy. I think your plastic housing likely is not low surface energy, so the epoxy probably should work fine.

 

[ScottyUK]

This material gives a pretty good bond to most of the bondable plastics given adequate surface preparation. Not much use on polypropylene, but then very little is. I came across it from the marine industry and have used in a few applications where I absolutely do not want joint failure. So far I'm happy. So far... ;-)