Epoxy on plastic

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brockrwood

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I don’t want to start another “glue war” but this surprised me. In a good way.
Yet another fin popped off of the Estes Oracle camera rocket after this big, tough bird landed on a patch of concrete. I had been gluing the plastic fins back onto the plastic bottom of the rocket with good, old Testors model airplane glue (plastic cement).
The fins kept popping off on even moderately hard landings.

This time I tried something different. I sanded the root edge of the fin to roughen it up. I sanded the slot on the plastic bottom of the rocket, and around it, to roughen up that surface, too.

Then I glued the fin on with Devcon “2 ton, 30 minute epoxy”. I must admit I wasn’t going for aesthetics. I slathered on the epoxy. I let it cure for 24 hours. I think that sucker is on there pretty good now. See pics.
354A97FF-C84B-4EC5-8074-7A9B9CBC1A12.jpeg

43BDF35F-8B8D-4C2E-8C3C-BA74F86BB363.jpeg

I did not think epoxy would work well on a plastic to plastic bond, but apparently it does if you roughen up the parts to be joined with sandpaper first.
 

David Schwantz

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Looks as if fin on left in pic is popping off a bit. Might be good idea to do same there. Don't aim for concrete. :)
 

neil_w

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Epoxy for plastic-plastic joints may not be the strongest, but in my experience it is certainly way better than the Testor's stuff (as is almost everything). I used to have a double-syringe (hate those things) of plastic epoxy but stopped using it because it reeked to high heaven. Now I just use my BSI for such miscellaneous tasks, either 15 or 30 minute.
 

mtnmanak

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Using epoxy to coat the joints certainly will make them stronger, but have you considered trying Plastruct Plastic Weld for gluing the plastic parts in? It is way better than Testors' stuff and easier to work with. I have used it on everything from Saturn V builds to on-the-field builds of small plastic rockets. A couple months ago, I took my nephew to his first launch. We put together an Estes Neon Tiger at the field using CA and Plastruct and were up and flying it in about an hour with no issues. He loved it! Stuff just works. The Plastic Weld works very well for bonding different plastics or if you aren't sure which kind of plastic you are dealing with. If you know the parts you are gluing are Styrene, their Bondene product is excellent as well.

I also have Testors and Tamiya liquid plastic bonding products, but I have found the Plastruct products work better.
 

JohnCoker

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Roughing up the surface was key. Epoxy doesn't have any special properties that make it better or worse for plastic. The issue with epoxy and plastic is that plastic is normally so smooth that epoxy can't lock into the surface. (Epoxy forms a mechanical bond, unlike material-specific adhesives can.)
 

boomtube-mk2

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Testors'' Model Cement is formulated for one type of plastic and only that one, polystyrene is what I believe it is called.
And technically it is not a "Cement" but a "Solvent" for that type of plastic, melting the surfaces of the items to which it is applied which then "De-Melt" back together forming, hopefully, a single piece of plastic.

For any other type of plastic for which it is not formulated, and there's about a million of them, Testors' simply acts as a surface tension bonding agent* and you might as well use wood glue in those circumstances.

*For lack of a better description.
 
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bjphoenix

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What I'm interested in is something to bond to the Estes-type blow molded nose cones (particularly for a build I have in mind).
There are glues I've used that seem "sticky" and like they would stick to anything. Something like a rubber cement comes to mind. I wonder if polyurethane construction cement could work too. I'm thinking if there is a glue like that that would stick to the white plastic then you could paint on a layer of it, let it dry, then epoxy could stick to it.
 

OG1959

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In the 70's I used Duco cement for all kind of things. It's not for use on polyethylene or polypropylene plastics. I think Estes nose cones are Styrene.

Duco Cement PDF
 

brockrwood

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The main thing when sticking things together is to know what you're sticking. If you cannot identify, then cleanliness, roughness and properly mixed epoxy are usually your best friend. And masking tape to preventing getting it on the bits you don't want.

Plastic identification 101

View attachment 475220
Sadly I can’t set the bottom part of my Oracle rocket on fire. :). I think the fins are styrene but the bottom part of the rocket (with the motor mount and slots for the fins) may be polyethylene. That might be why the Testor’s plastic cement wasn’t holding well. In any case, the epoxy on the roughened surfaces made a bond like iron. Epoxy on properly prepared surfaces may be my “go to” glue now when I really need something to stay glued together.
 

Back_at_it

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Learned years ago that plastic model glue doesn't work on Estes plastics. Super glue does a good job on most but if you really want a solid bond then you're looking at Epoxy.

Back in the day, I had tons of issues with my Maxi Alpha popping fins off almost every flight. Finally said screw it and pulled them off, sanded and installed with Epoxy and Epoxy fillets. Hasn't failed since.
 

davel

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Research Methyl Methacrylate Adhesives (MMAs). Structural adhesives designed to bond to hard to glue plastics as well as more conventional materials.
 

rocket_troy

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I've successfully bonded JB Weld to PVC. I generally don't use it, but it's the only thing I could find to surface bond and fillet fins to a PVC pipe some 25 years ago. Unfortunately it was too brittle for long term but the actual bond was robust,

TP
 
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