Advice needed about choice of adhesive

While this is not strictly metal related, I'm sure I will get some good advice here.
I need to stick tiny (about 1/8th inch dia) rare earth magnets to
plastic film (think laminated paper) and I am looking for a glue to do the job. The result needs to be fairly difficult to break.Tried CA, but I can break the bond with some effort. Same with Araldite (epoxy).
Any suggestions? Any tips to get it to work better?
TIA - I'm back to lurking now Gautham
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It depends entirely on what kind of plastic film you're dealing with. In some cases, there is no adhesive that will produce more than a superficial bond.
You really have to know what the plastic is. There's no getting around it.
-- Ed Huntress
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Just used some of this stuff to glue a magnet to some "King Board" in my trailer, double sided acrylic body trim tape didn't stick at all but this seems to be holding so far:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXCX69&P=SM
Think it's the same family of adhesives as "shoo goo". It's a little flexible but should do the job...

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On Tue, 13 May 2008 23:32:24 -0400, Ed Huntress wrote:

And the magnet. The rare-earth alloys are highly prone to rust, and many of the magnets are chrome plated. In addition to the difficulty of sticking to the plastic, you may need a glue that can handle the chrome plating.
OP: Are these magnets chromed? Are you having trouble with the bond to the magnet, or the bond to the plastic/paper?
--
Tim Wescott
Control systems and communications consulting
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wrote:

How about placing a "twin" magnet on each "side" of the plastic, with say some glue under each. That should almost double the strain required to remove one.
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On May 13, 5:21 pm, snipped-for-privacy@gmail.com wrote:

I'd ask 3M http://solutions.3m.com/wps/portal/3M/en_US/Manufacturing/Industry/Product-Catalog/Bonding-Solutions /
Karl
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There may be a problem that is more difficult than adhesive. When you say "rare earth magnet" I assume you are using Neodymium-Iron-Boron magnets. I used these to make refrigerator magnets with epoxy for a while. The neo oxidizes very badly. When you bond with epoxy it is strong for a while and then a film of oxide forms between the magnet and the adhesive. Then the magnet falls off. You need to get an airtight coating on the magnet before bonding. I have seen plating that lasts well.
The problem is the Neodymium, it is the material that makes sparks in cigarette lighter flints. It is very oxidizable (flammable in powder form).
I never solved the problem. By the way I still have hundreds of magnets to sell. They are about .2 dia x .4 inches long.
Good luck. Bob
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On Tue, 13 May 2008 20:21:55 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

==========\ I would try using a hot melt glue gun while you are waiting for information. As fast as the hot melt sets up, your biggest problem may be positioning the magnets. Make a trial for 2.97$US +SHT click on http://www.lowes.com/lowes/lkn?action=productDetail&productIdt451-412-MT300&lpage=none
for more info see http://www.glu-stix.com / http://www.glu-stix.com/shop/page/Polyamide_Glue.html and for metal/plastic bonding see http://www.glu-stix.com/shop/page/product_detail/Product/67136cccf00d511637cd2e7ece2b38b7.html also see http://www.hotstik.com/store/pc/HS-376-UltraBonder-Glue-Sticks-Per-Lb-6p43.htm
Unka' George [George McDuffee] ------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).
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Will try those hotmelt varieties.
The bond seems to give up on the plastic side i.e. there is adhesive on the magnet which seems difficult to get off but the plastic surface is clean.
Wondering if roughing up the plastic film with a bit of sandpaper will make any difference.
Thanks, Gautham
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On Thu, 15 May 2008 02:55:23 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

==========Be sure to let the group know how things work out [enquiring minds want to know...]
Unka' George [George McDuffee] ------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).
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On Thu, 15 May 2008 02:55:23 -0700, gautham.vanya wrote:

While it makes a difference, other methods are more effective. From page 355 at the end of section D, "Surface Grafting" of "Adhesives in Joining Plastics", a chapter in Patrick and Minford's "Treatise on adhesion and adhesives": "increases in adhesion were seen" (by abrading under epoxy vs abrading in air) but "failure surfaces of the adhesive bonds were apparently adhesion failure" vs. "Yamakawa's work in which grafted surfaces exhibited primarily substrate failure in practical adhesion testing." Yamakawa grafted saponified methyl acrylate on PE, PTFE, and PCTFE surfaces, via Co60 radiation -- impractical to try unless you work in a hospital with a radiation-therapy department.
http://www.corotec.com/techinfo/papers2.html?id 7131402 describes high voltage RF plasma techniques that are commonly used to prepare PE surfaces for printing and gluing. Also see the chemical surface preps (for metals but maybe relevant to some plastics) described in http://www.wmrc.uiuc.edu/info/library_docs/manuals/coatings/surface.htm many of which are practical at home.
-jiw
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Keywords:
snipped-for-privacy@gmail.com wrote:

I came in on the middle of this thread, so I'm not sure what sort of plastic you are working with. There areseveral possible contributing reasons why adhesives don't stick to plastic:
1) Residual monomers. These can be oily, and prevent the adhesive from attaching to anything structural. The right solvent can clean off a lot of this.
2) Too smooth a surface. The adhesive just can't hang on to anything. Thsi is where roughing it up will help.
3) No molecules on the surface that want to hook up with the glue. If all of the ploymers in the plastic are long chains happily hooked together, the adhesive can't find anything to chemically bond with. This is sort of like 2, only at the molecular level. Chewing it up with abrasive may help, but chemically etching the surface to break up the long polymer chains is best. Sometimes you can achieve soemthtign similar by lightly scorching the surface. The chemicals required to etch some plastics are pretty nasty.
For most things, I use some sandpaper & then give it a good cleaning with a solvent.
I haven't used it myself, but I've heard good things about the Cyanopoxy system:
http://www.coolchem.com/index.cfm?fuseaction=cyanopoxy
Doug White
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Where's the bond part, from the magnet or the plastic? Divide & conquer, so to speak.
Hul
snipped-for-privacy@gmail.com wrote:

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