Epoxying over epoxy

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bertaadele

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I have a quick question for everyone. I applied rocketpoxy on the first fin of my FG rocket and it is sagging quite a bit. What is everyone's take on putting epoxy over epoxy Can I just apply it later as a new piece of my fillet or do I need to sand the epoxy first?
 

OverTheTop

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If it is still "green" and not gone off completely you can just add on top I believe. Once cured you need to rough up the surface to get a decent bond.
 

TheTellurian

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Always clean the epoxy with a wax solvent like floor wax remover or ammonia irregardless of what you do. Epoxies, most varieties anyway, create whats called an amine blush. That is a wax like substance and is what prevents good epoxy to epoxy adhesion. Sanding without cleaning just moves the waxy amine into the scratches from the sand paper.

Epoxy is just plastic, you may be able to heat the joint with a paint stripper gun and bend the fin back into place holding it while it cools.


Richard
 

bertaadele

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Always clean the epoxy with a wax solvent like floor wax remover or ammonia irregardless of what you do. Epoxies, most varieties anyway, create whats called an amine blush. That is a wax like substance and is what prevents good epoxy to epoxy adhesion. Sanding without cleaning just moves the waxy amine into the scratches from the sand paper.

Epoxy is just plastic, you may be able to heat the joint with a paint stripper gun and bend the fin back into place holding it while it cools.


Richard
So clean with that and then sand? Can isopropyl alcohol still be used to clean the sanding dust off, or will that affect something detrimentally?
 

prfesser

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Always clean the epoxy with a wax solvent like floor wax remover or ammonia irregardless of what you do. Epoxies, most varieties anyway, create whats called an amine blush. That is a wax like substance and is what prevents good epoxy to epoxy adhesion. Sanding without cleaning just moves the waxy amine into the scratches from the sand paper.
Amine blush is water-soluble. Warm soapy water and a ScotchBrite pad. Rinse thoroughly.

Best,
Terry
 

TheTellurian

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Your right. I just checked it out and it is water soluble. That it is often referred to as waxy and a statement by someone who I thought knew what they espoused [not] led to my misconception. None the less you want it gone before applying an overcoat whether epoxy or paint.


Richard
 

bertaadele

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Thank you everyone! I tried this last night and it did lose the shininess.ImageUploadedByRocketry Forum1500898541.280273.jpg ImageUploadedByRocketry Forum1500898563.181909.jpg
 

Steve Shannon

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Always clean the epoxy with a wax solvent like floor wax remover or ammonia irregardless of what you do. Epoxies, most varieties anyway, create whats called an amine blush. That is a wax like substance and is what prevents good epoxy to epoxy adhesion. Sanding without cleaning just moves the waxy amine into the scratches from the sand paper.

Epoxy is just plastic, you may be able to heat the joint with a paint stripper gun and bend the fin back into place holding it while it cools.


Richard
You cannot melt and reform epoxy. It's a thermosetting resin, not a thermoplastic.



Steve Shannon
 

TheTellurian

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I didn't say melt the epoxy, The intention was to raise the temp above the Tg of the epoxy where it becomes soft and can bend. Lots of discussions on how to avoid this in the HPR forums.


Richard
 

Steve Shannon

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I didn't say melt the epoxy, The intention was to raise the temp above the Tg of the epoxy where it becomes soft and can bend. Lots of discussions on how to avoid this in the HPR forums.


Richard
You may be right. I've used heat guns several times to soften epoxy to remove parts, but I've always believed that heating to that temperature destroyed (or at least damaged) the integrity of the already cured epoxy.


Steve Shannon
 

TheTellurian

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Many epoxies can be post cured at temps at or just below their Tg which causes a more complete cure giving the full strength capable from it. As long as it doesn't go too far past that I think it will be alright but I have no reference to validate that opinion.


Richard
 
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