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Adhesive for plastic contianers

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Recently we were working on creating out first cache which included magnets on it. After the first design failed i spent much of Saturday reading through thread after thread of information on suggestions for adhering items (mostly magnets) to plastics (mostly polypropylene and polyethylene.)


Upon reading most all the threads i could find on the subject i basically came to three adhesives that were not only recommended by a lot of users but available in my area. The list i came up with was:


JB Weld

Gorilla Glue

Outdoor Goop


I contacted all three companies to see what they said about their products adhering to the polypropylene and polyethylene.


JB Weld said it would not.

Gorilla Glue said it would not adhere to either the plastic or the magnet as it needs a porous surface.

Outdoor Goop said in their tests Outdoor Goop did not create a strong bond but i could test it to see if it works for me.


I just thought i would share what i found. Other users have put what i think was a pretty good description of this is that mostly all adhesives will not adhere to this type of plastic. (Although at least one person did show an adhesive that would adhere to it. I didnt do too much research on it because it appeared to not be cost effective.)


In the end, as was suggested to others before us, we used stronger magnets on the inside of the container. We did use gorilla glue to attach the magnets on the inside of the cache to the plastic. It seemed to hold fine for now anyways. Now all we can do is hope no one tries to take them as swag.


I would have posted in an older thread but this applies to more than one thread.


BTW the adhesive we originally used was silicone. Its an amazing adhesive- but not right for this type of application.


Happy caching.

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I'd be interested in other folk's attempts as well. My latest magnet attempt involved attaching rare earth magnets to the bottom of 8 old time aluminum film canisters. I started with JB Weld, then tried Gorilla Glue, and finally 2 ton epoxy. In all three cases, when the bottom of one canister came in close proximity to another, the magnetic force was stronger than the adhesive. Like you, I ended up gluing the magnets to the inside of the film canister.


(tech note: in all 3 attempts, the glue separated from the aluminum, not the magnet)

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I have not attempted to attach magnets to plastic but I have come across this problem when needing to assure a good bond with building materials. You might want to try drilling small holes into the bottom of the containers and magnet so the glue/epoxy can ooze into the holes making a dowel out of the hardened glue.

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The problem with most glues is that once they harden, the flexing of the plastic will cause them to pop off. Therefore, I used Goop for this purpose. It worked well.


While I did scuff up the plastic prior to gluing, I did not drill holes in the container. I did not want to risk causing the container to leak.

Edited by sbell111
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I've glued rare earth magnets on the inside of Lock and Lock containers with black RTV silicone and had good luck so far. I then cover the magnets with duct tape so they won't get knocked loose if they're bumped. Rough up the plastic a little with sandpaper before applying the adhesive so it has something to stick to.

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Having extensive experience with bonding things (mostly in the concrete arena) I can tell you that the two biggest factors in a good bond are typically:


1. The compatability of the product you are using with the product you are bonding to.

2. The surface condition of what you are bonding to.


Read product instructions carefully. They are typically accurate and will normally give expected results if followed properly. Sometimes people try to bond things that bonding agent isn't compatible with. Sometimes the surface needs to be roughed up to assist with bonding.


Not all plastics are created equal...same with metals. Someone could probably do an extensive write up on various test results. Sometimes it's just good old fashioned trial and error.


There are ton of different epoxies out there...seems like sometimes the two part more health hazardous kind are strongest, but the one part epoxies have come a long way.


Another thing to consider is hardness...some epoxies can get so hard that they won't contract and expand at the same rate as what they are bonded to and in extreme cold or heat that may cause the bond to break.

Edited by egami
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Note in these threads - the OP states polypropylene. AFAIK - there is only a few commercial products that will bond poly. 3-M has one - but very expensive and only large quantities.


Poly continues to leach - not the correct term - but close - an oily substance for most of it's life.


You can plastic weld it - if you have the proper equipment and inert gas.


Noe PLASTIC - that is a very general term - ABS, styrene, nylon, etc. all react differently.


Poly - very very hard to do - I had a poly canoe and needed to repair it - actually tape, adhesive, etc. will stick better than glue - but it's almost all temporary.


Epoxy will not stick to Poly - but will to not to poly.


For the OP's original question - I'd try double sided tape, Gorilla tape, or even another magnet inside the container (magnet sandwich).


Link to 3m tech. on Poly glue that WILL work.


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As a general rule, the best thing to do is to get a somewhat stronger rare earth magnet than you might think you would need, and attach it to the inside of the container. You can use glue, but on the inside of the container duct tape often works well enough. Trying to keep the magnet on the outside of the container is usually a losing proposition.


ETA -- uh, yeah. like the OP said. (blush)

Edited by WalruZ
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