High temperature epoxy?

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mad4hws

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Hi everyone,
Wondering what the epoxy of choice is for high temperature rocket applications. I'm making a motor tube for Mid-power out of Soller Composites Kevlar/Carbon Fiber weave and need something that can stand up to the extra heat. I have used West System with 207 hardner, but I don't think that is sufficient.
 
I use JB weld to tack and Proline 4500 for fillets on all my minimum diameter rockets.
 
Motor tubes don't get as hot as everybody thinks. If that were the case, would they make them out of cardboard?

I think considering you are using Kevlar/CF, whatever 'normal' epoxy you are used to using will be fine.

My $.02....
 
JB Weld is the high temperature epoxy of choice. But the simple truth is, motor casings just don't heat up that much.
 
You didn't say "minimum diameter".
When I am making a motor mount that will be buried inside I use the cheapest glass available. "Coremat", matte, or e-glass. For resin, most high temp epoxies are too stiff for laminating. Polyester resin has low viscosity, higher temp resistance than laminating epoxies, and it is cheaper.
 
I was under the impression that aero heating is a bigger concern than motor tube heat, but it is not like I have done any tests.
 
Its for a mid power nothing is getting that hot in the short amount of time. F-10 probably longest burn mid power.
 
Did we all mis-understand the OP? Mad4, are you talking about making the motor case out of kevlar-carbon composite? 'Cause I answered the "motor mount" question, not the case question.

In which case, (pun intended) you are gonna need something besides an off-the shelf epoxy. Something phenolic, or thermo-setting. I would go right to pre-pregs and a autoclave. Hand-layup, with the high-temp epoxies that I am aware of, JB, Cotronics, etc., seems iffy. The fibers may not saturate, and there could be air, or a significant layer of epoxy separating the fabric layers - weakening the structure.

You could buy a lot of single use motors for what you would spend learning how to do this without kabooms.
 
I know this is off topic, but I used JB weld for fillets on my L1 rocket, Im looking at doing a 54 minimum diameter for my level 2, would it be okay to use JB weld for fillets as well? Should I go with something better? The other epoxies im looking at getting is proline 4500, and rocket poxy.
 
Are you doing the MD to chase speed, or altitude? JB is heavier than it needs to be.

4500 for the root, Rocketpoxy for the fillet seems like a common method ( that I'm liberally borrowing ).
 
Are you doing the MD to chase speed, or altitude? JB is heavier than it needs to be.

4500 for the root, Rocketpoxy for the fillet seems like a common method ( that I'm liberally borrowing ).

Either way is good. Most find rocketpoxy better for sticking things together, and 4500 flows better for fillets. Properly done, the fillet will provide most of the strength.
 
Just a week or so ago I was in need of some "high temp epoxy"..........................for the radiator in my van.

Drain plug on my radiator broke. Don't know how, but somehow it snapped off with the part that has the little tangs to hold it in place still in there. Not enough to keep it from leaking of course. Now, due to space to work issues I couldn't get that little snapped-off bit out of there without pulling the whole radiator, which is either a major pain in the butt job for me to do myself, or a pretty expensive one for me to farm out. Neither of which I wanted to deal with. Keep in mind a new plug is about $5 - but I had to get that old piece out of there first. Grrrrr. So, my local trusted mechanic told me that I could always epoxy the broken-off piece back in place........cheap, quick, and easy. Of course this means that if I ever drain my radiator it will be a bit of a pain, but nothing too serious. Sounds good to me, so I opted for the "hillbilly"/"ghetto" fix (note that you can choose whichever phrase is most/least PC for your own sensibilities here - offend or avoid offending however you care to).

What was my "high temp" epoxy of choice? ------- JB Weld.

Worked great. Made sure everything was as dry/clean as I could reasonably get, and just glopped a whole bunch in there and stuck the piece back in place. Since then I took a road trip that took me up long steep climbs and through hours of driving across the hot desert - this over a couple of days that made national news about a major heat wave hitting us here in the southwest. I put in about 600 miles with air temps getting upwards of 107 degrees. You know my radiator was running way hot. Planes in the area were grounded, lots of emergency issues due to the heat blast, people frying eggs with just a frying pan in the sun, and all that. But the epoxy held.

Works for me.

s6
 
Mad4hws,

Most of us are well served by West or US Composites 100MPa resin system with 55’C glass temperature. Because polymers don’t really melt we discuss glass transition. There the coefficient of thermal expansion increases approximately ten fold. The resin expands faster than before. Tensile strength decreases and elongation at break increases. We approach goo about 200’C and pyrolysis about 260’C.

You won’t find a lot of technical data on JB Weld. Is a cult of personality?

MSDS show it is filled bis-A resin as anyone could fabricate from West or US Composites. Doubt you’ll find a published glass transition temperature. If you did it would probably be 60’C. I’m sure they claim ultimate service temperature at common 260'C pyrolysis.

Fair enough. Let’s hear from the JB Weld fan club. Can’t be true, right?

Feckless
 
I'm planning on going for altitude with it. I'm going to put an L935 in a 54mm Tomach or a 2.6" screech with the 54mm motor mount. Both sim to 19,800 feet, and Mach 2. I'm hoping for 20,000 feet. Still trying to decide which one to get. I'm leaning towards the Screech. I'm gonna put an Eggfinder with better antennas, as well as the Eggtimer quantum and a classic Eggtimer for redundancy.
 
I've flown a 54 mm carbon fiber Mongoose on a L935 that went to Mach 2.3 or so. I did not do anything other than using the Proline epoxy that came with it. IIRC it went to about 22,500 feet.


Tony
 
Only thing I know that has a guarantee is Cotronics stuff like 4525IP. Any higher than 500 degrees and Cotronics other adhesives must be baked in an oven to get it to cure and withstand temps higher than 500 degrees. 4525 is room temp cure. That said, I always thought J&B was only good to 300 but I see a data card has been published that says it's better for more. Proline 4500 looks like some
formulation along the lines of 4525, I think the "black" is carbon black added to the mix along with "other stuff". I've never seen a formal spec sheet for it
but hearsay says it's good high temp epoxy. Besides, it's a heck of a lot cheaper than the Cotronics products. I find Proline very tough and easy to work with.
My absolute favorite in the past, though very heavy stuff was Power Poxy Weld. I could get it to reflow with a heat gun at least 3 times to shape a fillet. Not only
that, the transient decrease in viscosity really penetrated the pores of whatever was being bonded. Most epoxies, hit it with a heat gun carelessly and WHAM they
setup up quicker. Power Poxy would nearly liquefy, soak in and then it did start to gel up faster with the application of heat. It was a heavy product though.
It's out of production. I think the company just closed up and disappeared.

I did a post mortem on a 4 inch cardboard rocket and dissected out the TTW fins from the 4 inch cardboard tube. I could not snap the fillet off the plywood fins and had to use a screwdriver chisel to gouge it off. That stuff was strong. Did the heat reflow, liquefy, gel routine and it really bonded and soaked into the grain of the 40 grit sandpaper prep of the plywood fin surface. It was a heavy epoxy but I haven't seen anything perform like it since. (Anyone knows of another
product that behaves like this, post it as I'd like to try it.) Kurt
 
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JB is in a class called "metal filled epoxy". These are (typically) 2-part resins/hardners with microscopic-sized particles of metal mixed in to give strength. There are several different metals used, from aluminum to steels (including stainless), even titanium. A quick google search on the subject gives me this page:
https://www.masterbond.com/applications/aluminum-and-stainless-steel-filled-epoxy-systems
The SteelMaster HT43 has a service range from -60 to +400F. I bet there are other brands that exceed the higher temps. I also bet that a carefully worded letter to a company's sales/engineering support department could yield some "engineering samples".
 
Sounds like he (she?) is rolling his own motor tube from scratch, in which case adhesive epoxies (e.g., JB Weld and Proline 4500) are not what you'd want. I've used HTR-212 from Aircraft Spruce with good results. It is a high temp laminating epoxy with room temperature cure, is relatively inexpensive, and would be sufficient for making a motor tube from carbon/kevlar weave.
https://www.aircraftspruce.com/pages/cs/epoxy_0browse/htr212resin.php
 
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