Properly bonding composites and what your government doesn't want you to know.

[Grog6]

There is some reason isopropanol is better than acetone; something about it leaving the epoxy in the fg degraded and less strong. Yes! this is it; it destroys acrylic and polyesters. Don't use acetone, use alcohol.
200 proof Ethanol is best, but expensive.

 

[MJW]

Why is Everclear better than Isopropyl electronics cleaner? Clearly rubbing alcohol can have contaminates added, but 99.9% pure anhydrous IA is a pretty clean solvent. Is ethanol just a more compatible molecule?

 

[6inchmonster]

There is some reason isopropanol is better than acetone; something about it leaving the epoxy in the fg degraded and less strong. Yes! this is it; it destroys acrylic and polyesters. Don't use acetone, use alcohol.
200 proof Ethanol is best, but expensive.

Personally I think it is better because it does not get me drunk/high thru osmosis :-/

 

[tsmith1315]

Why is Everclear better than Isopropyl electronics cleaner?

Everclear is only 190 proof, ~5% water.

 

[Grog6]

If you pour anhydrous ethanol to the brim in a shot glass, it will overflow in a few minutes.
It sucks up moisture out of the air.
86% is the best you can get without chemically dehydroxifying it.

Let's remember how bad acetone is for us; I'd hate to have my liver fall out.
I remember the buzzwords now, coffee is wonderful.
Ethanol leaves a" low surface energy surface"
I worked with PCB's and RTV a lot.

 

[Grog6]

Personally I think it is better because it does not get me drunk/high thru osmosis :-/
A spray bottle of everclear is a dangerous thing, lol.
I use it and isopropanol in the garage. Clear marking is important!.

 

[OverTheTop]

PCB's

Polychlorinated biphenyls or Printed Circuit Boards?

 

[BDB]

I'm guessing ethanol is preferred because it evaporates better than isopropyl alcohol, so you don't have to worry about residual solvent getting trapped in the epoxy. But the pure stuff is difficult to get. I'm an organic chemist, so we have plenty of 200 proof ethanol in my lab. There is way more paperwork to sign to buy it than there is to buy cyanide.

 

[Grog6]

ircuit boards; I are a PCB designer(EE)

 

[prfesser]

If you pour anhydrous ethanol to the brim in a shot glass, it will overflow in a few minutes.
It sucks up moisture out of the air.
86% is the best you can get without chemically dehydroxifying it.

Correction: 95% ethanol is the maximum that can be obtained by distillation. That concentration makes the mixture an azeotrope, that is, distilling 95% ethanol gives a product that is still 95% ethanol. When 100% ethanol is needed, one way to remove the last 5% is by adding calcium oxide (CaO, "quicklime") to the distilling pot; it reacts with any residual water.

 

[Grog6]

My bad, my memory is toast since my stroke. I'd fail that semester for sure.

 

[Homer_S]

I'm guessing ethanol is preferred because it evaporates better than isopropyl alcohol, so you don't have to worry about residual solvent getting trapped in the epoxy. But the pure stuff is difficult to get. I'm an organic chemist, so we have plenty of 200 proof ethanol in my lab. There is way more paperwork to sign to buy it than there is to buy cyanide.

On account of the revenuer's need to get paid. When we use it in the lab, it doesn't get sold where ethanol is normally taxed.

Homer

 

[kramer714]

So we’ve got lacquer thinner, acetone and denatured alcohol available in the rocket barn.

Looking for the best prep solvent for an “R” powered G-12 fiberglass rocket that we’re just starting to build. Read the entire thread twice it’s so chock full of great info.

For the maximum cleaning of the G-12 what’s the consensus on which of the above is the best to use?

Thanks!

Chuck C.

Acetone is best, it will help remove the mold releases used when the fiberglass is made, wipe then sand then wipe. If you prep ahead of time, a quick wipe with with alcohol works to 'dust' the surface.

Use clean oil free wipes, Kim Wipes or some generic knock off work best.

Mike (actual aerospace composite engineer) K

 

[ThikeHigh]

Step 4 epoxy application:
Ideally you will be doing this step immediately after Step 3. Grab your epoxy of choice. I chose this one because it was in the gun. Apply a decent bead of epoxy and spread it on. Its better to have to much than to little. We want enough so that we can clamp and push out all of the air in our bond.

Too much and too little, not to. When you are over or under, use two o's.

 

[rharshberger]

Too much and too little, not to. When you are over or under, use two o's.

okay, grammar police, on a dead thread no less.....

 

[ThikeHigh]

Sorry, I ma a retired English teacher and just trying help you,

 

[Steve Shannon]

Sorry, I ma a retired English teacher and just trying help you,

Correcting word usage on a post that was written in 2013, in a thread that has been dead for nearly a year by a member who hasn’t been on this forum this year, is guaranteed to irritate some people, and frustrate yourself. It’s very easy to lose sight of the fact that the information imparted within this thread is the real value, and most of us understood exactly what he meant, even if he did say “to” rather than “too.”
Also, it’s very easy to mistakenly use a word with spellcheck turned on. For instance, in your response, which I have quoted verbatim above, you accidentally typed the word “ma” instead of “am.” We all do things like that. I’ve done it more times than I care to admit. This is a forum for the free exchange of ideas related to Rocketry. If we focus on the grammar rather than the message we quickly will lose participants who are either embarrassed to post, because they’re unsure of their grammar, or who are irritated by the recurring corrections.
So, ThikeHigh, please enjoy the forum. Learn and teach about rocketry. Contribute by posting pictures and well-written descriptions of your endeavors. As we get to know you and you get to know us you will find that rocketeers are friendly and forgiving. In the meantime, for your own sanity, I would urge you to ignore the frequent benign misspellings, and grammar gaffes, or you’ll feel like you’re in the largest game of whack-a-mole you’ve ever seen.

 

[tsmith1315]

Sorry, I ma a retired English teacher and just trying help you,

 

[SecondRow]

Sorry, I ma a retired English teacher and just trying help you,

For ’tis the sport to have the engineer
Hoist with his own petard;

— Hamlet, Act 3 Scene 4

 

[b.wieting]

Yes, I agree that the statement is incorrect and/or confusing. Presumably he meant sharing of electrons (in the "outer shell"), which is characteristic of chemical bonds.

However, I'm still not convinced that epoxy makes a chemical bond with fiberglass (silica). It might, but it needn't; the epoxy creates a matrix in which the fibers are embedded. Any chemists here able to clarify?

And in general, I think the original post has a lot of value. I've been sanding with finer grit and cleaning the surfaces before sanding also as a result of reading it. Things I've learned here are reflected in my recent Epoxy Basics video.

Siloxane primers have been incorporated into solar module encapsulant sheets like EVA to promote adhesion to the cover glass.

 

[SolarYellow]

Does anyone have a copy they can post, or an otherwise viable way to get hold of this doc? It's not even available via Wayback at this point:

https://www.niar.wichita.edu/niarworkshops/Portals/0/Jun17_0200_JimM.pdf

 

[bad_idea]

Jun17_0200_JimM.pdf

It appears to be here now:

https://faa.niar.wichita.edu/Portals/0/2004 FAA Bonded Structures Workshop/Jun17_0200_JimM.pdf

 

[Hobie1dog]

Too much and too little, not to. When you are over or under, use two o's.

I'm with you on this one.

 

[Lt72884]

love this stuff. On one of my rockets that used an upper L motor, i sanded the fins like i do for autobody work. I water sanded up to 3000 grit and had the perfect surface.
I have even thought of covering my wood fins or 3d printed fins in epoxy and sanding smooth. But at the altitudes my rockets go on wood fins, i think it would be more work than its worth haha