a good brand of epoxy

Loctite 4205. this is an industrial strength hi-temp instant glue. 4205 is the thick stuff, 4204 is the thin stuff. sticks to anything. will bond to skin and eyeballs.

but it holds pretty damn good.

rick
 
Years ago I used a 2 part epoxy that was used to mount the reflective markers on the hiway road beds, (and they are still using something like it) It has very good shock restance, I don't know what it's max temp. is, it was purchaced from Ev Roberts in La Calif. The 5 min is what I used, but I tried the 90 min (over night cure) and it was much stronger. Maybe a internet search?.

Scotch-Weld 3501 B/A gray, 3M Epoxy Adhesive, 5-7min pot life~ (over night cure @ 60 F)

Bonds; iron, steel, aluminum, copper, bronze, lead, glass, wood, concrete, some rubbers, some plastics, ceramics, not stated but asphalt also.
 
I found when gluing magnets the 5 minute stuff is way too fast. It might be OK if you only have one magnet to do.
I went for something with a 30min work time. Downside is it takes overnight to fully cure.
 
I was using PC7 , I'm not sure what the temp on it is, but it's supposed to be ok for engine blocks. It has fibers in it that make it good for repairs that might need to resist shocks. Since heat had ruined the magnets, my repair was not tested for long.
 
General epoxy information from a hobbyist. I am not an epoxy engineer.

These are general truths so far as I know. I've used epoxies all my adult life.

PS ADDENDUM: you cannot re-pour epoxy onto itself after the "amine blush" has occurred;
you'd get no bond then. In case of pouring over a previously epoxied surface, one must sand, roughen, tooth, key,
the surfaces! The West System people are so strong and respected in their line of marine epoxies, I bet that by now they have a comprehensive website containing all this information and more ( last used their products in 1999, and they were so excellent with customer help/information. I bet it's all online today.


=+The slower-setting the epoxy, the stronger and more heat resistant it is.
Marine grade (West System) epoxies are excellent. But so are any quality epoxies that are designed to set slowly. I generally use the hardware store syringe type stuff (slow set!!!!), but for my controller job I wanted the "best": a slow set designed for laminating table tops that must resist hot plates and platters.
I had a small kit on hand from many years ago. Beat buying a $50 or thereabouts, West System brand kit, and seems to give fine, equal results.

=Any liquid epoxy can be admixed with an almost endless variety of fillers in order to thicken the material against being runny. Anything from metal powder, plastic dust, talc (easy to sand). Again, the West System brand and other pro brands offer a variety of powders to admix into their liquid epoxies.
Glass microbeads are the most inert filler of all, and easy to sand and shape.

=Epoxy putties are filled epoxies with fillers of various sorts.

=Pure, liquid, slow setting epoxy is the least hygroscopic of all kinds.

=Slow setting epoxies are the most heat resistant.

=All epoxies completely soften to cheese-like strength and consistency in heat, and I mean in low heat: sub- 250F turns all pure epoxies so soft as to be removable by wire brush or dental pick. There is no extant "600F" epoxy, JB Weld claims are lies. Overheated epoxy, so long as it is not burned by the heat, returns to its original state of hardness upon cooling down again.

=Some epoxies are rock hard and would be considered brittle if the substrate is flexed.
=Some epoxies are less than rock hard, and will endure some flexing.

=Bonding: Absolute cleanliness. Solvent wash more than once. The slightest trace of oil, invisible,
will compromise the bond.
=More about bonding: some materials have a natural affinity to bond fully (if they are clean) to epoxy.
=Many materials, mostly plastics of polyethylene type, cannot chemically bond to epoxy; they are "non polar" to epoxy.
In these cases a semi-reliable mechanical bond can be gotten by coarse sanding of the surfaces.

=Epoxies of the slow set, hard kind, are the least hygroscopic of all coatings...far superior to water ingress, long term, than polyester resins, which otherwise seem so similar.
It is for this reason that premium watercraft are gel coated with epoxy and not with the much cheaper polyester resins of yore: Polyester resin boat gel coats eventually blister and fail if the boat is constantly kept in water.

RTVs: silicone rubbers are excellent aids, but are, for sensitive work, sometimes not suitable: they are all hygroscopic. That is, if the item is going to be submerged in water long term, the silicone "rubber" stuff will take on a considerable percentage of water, though it will not blister or "leak" massive water through to the substrate.

I favor the marine epoxies, slow setting (I used to use West System when I worked with old cars and their wooden frames. Nothing is better for wood reinforcement and filleting and even for "saving" rotted wood, than a very slow epoxy: it will wick well into well-dried wood before it sets up.

For my submarine ebike controller, see the gradual progress at my "show your ebikes thread".
I think it will work. ONLY the controller board itself is "potted"; and I won't be relying solely on
the table-top coating resin chosen for this job.

See my thread for updates, reasonings, and best guesses. I'm not an expert, but I do have some
slight experience with epoxies for some decades, and hope to have a submarine-capable ebike before long. The controller enclosure: completely open to the cooling, drying breezes. It will be a cool little eZee controller, thanks to waterproofing the part that counts: the board and its wire-take off points.

fwiw, hope this helped,

Reid
 
Great info, Ried. I tend to use the marine grade pc7 since I keep it on hand to ding fix the windsurboards. Without knowing it, I had the good stuff. :shock: I have sworn by pc7 over jbweld for years ever since I glued a skillsaw back together with it. It held for years, and I'm talking daily use on a framing crew building houses. Can't treat anything rougher than framers do. I knew pc7 could take some heat since it stood NM summers when the saw would get too hot to touch without gloves.
 
This thread was as close as I could find on Epoxy.

I am on the hunt for a high-strength epoxy with excellent thermal conductivity, though having low electrical conductivity. An internet search revealed this one site meeting the criteria: Thermally Conductive Resins

Of the epoxies listed, 50-3150FR appeared to have the best qualities. The specs suggest deformation begins above 155°C, and that’s acceptable because Aramid also begins to age and elongate at 160°C. The magnets I intend to use operate well below this amount. The 50-3150FR product has good shear strength and is very hard, meaning it won’t flex very much. The idea is to pot the aramid-covered stator with an excellent thermal epoxy to help shed the heat.

I’d like to think that this is a good start, although would welcome alternatives. Thus I ask the community, those that have used thermally-conductive epoxies, to relate their experiences, the brand and product they have used, as well as the specifications if possible.

ADDENDUM: The stator I speak of is for ironless AF machines. :)

Thanks kindly, KF
 
I have been making my own thermal epoxy by mixing silicon carbide with liquid epoxy. Search Ebay for carbide powder and carbide grit. For the highest solids loading, you want to mix fine and coarse grits... but finding the best mixture involves voodoo and black magic.
 
That’s some fantastic stuff silicon carbide; thermal conductivity is greater than diamond!

Questions, questions: I understand that it could be a semiconductor with the right doping.
  • Do you worry about that in your use of the epoxy mix?
  • Is the material affected by high magnetic flux?
  • What have you used as a high-strength epoxy?

Thanks for the intrigue; it is a fascinating material!
Cool, literally! KF 8)
 
SiC thermal conductivity is quite a bit less than diamond... I also use diamond for making thermal epoxies.

The greenish grit that I use is totally insulating (multi-gigohm resistance). Magnets are not a problem. One issue can be it is VERY abrasive (can you say carbide sand paper?). Might be an issue with magnet wire if you don't get a good fill into the windings.

I use 1500 grit for attaching LEDs. Mixed with coarser stuff for potting modules. For low end applications, I use West Systems epoxy.
 
What about the stuff Dr Bass recommends for his torque arms. The 60 min stuff (Scotch 460?) was mentioned as being developed for holding down motor magnets.
otherDoc
 
texaspyro are you still around? I have epoxy questions :)

What did you use for a base epoxy on your mixtures?

Linking to another epoxy thread:
Very Good Magnet Bonding Epoxy

Cheers, KF
 
How'd your thermal epoxy plan go? You ever test it. It seems a possible way to get rid of a lot of heat as there's a lot of extra room in the motor you could fill with fin-shaped epoxy. Maybe make a simple mold. I think the fins would make it much more effective
 
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