Recent notes on epoxy from January 06, 2007:

There is a very wide variety of epoxies on the market.

Epo-Tek, which is just one company offers over 50 different thermal epoxies, each one with different properties:
http://www.epotek.com/categories.asp?ID=2

Epo-Tek offers about 50 different optical epoxies:
http://www.epotek.com/categories.asp?ID=3

They offer about 50 different electrical epoxies:
http://www.epotek.com/categories.asp?ID=1

They offer about 30 general epoxies:
http://www.epotek.com/categories.asp?ID=4

If you register, there are over sixty technical papers to help folks address their specific needs, and to help them do a better job when using epoxy:
http://www.epotek.com/ssc-sign-in.asp

If you have a specific application, you can use their keyword search to help narrow down from the wide range of choices:
http://www.epotek.com/ssc-product-rec-key.asp

Unfortunately in rugged environments, long term, epoxies don't usually perform that well unless you know what you are doing, and then utilize it properly. Even then you can have issues. I've even seen lifelong epoxy scientists scratch their heads over field failure mechanisms. That is why there is such a wide variety of epoxies on the professional market, some are made to bond certain similar metals, some dissimilar, or bonding metal to glass, where you have CTE mismatches, or for things like rapid temperature changes.

Another specialty company, that is a bit more expensive, is Masterbond. They offer over a lot of different grades of epoxy:
http://www.masterbond.com/overview.html

They have 81 generic materials that are common use items, there are many more that are not listed in this quick selector guide for two component epoxies:
http://www.masterbond.com/sg/masterbond_2ptsg.pdf

Basic bonding and surface prep is covered here in this guide by Loctite, another epoxy manufacturer, that makes hundreds of epoxies:
http://www.loctite.com/int_henkel/l.../pdf/ACF205.pdf

A number of their epoxies can be found here:
One of Loctite's epoxy lines

Some metal bonding information from Loctite:
http://www.loctite.com/int_henkel/l...ondingGuide.pdf

If you want to find one of Loctite's adhesives in your local area, call them, I once found rocket nose cone epoxy 1/4 mile away from me, at a pneumatic parts company, and as it turns out, they can nearly get any of Loctite's materials in 24 hours at no cost additional cost to me! What was nice about this material, was it's high temperature, it's high Tg point, and the fact that it could flex and take shock, high surface hardness, while still having a high bond strength, and even hold up under both high humidity and high heat situations at the same time. Most epoxies don't have all those combinations.

A real datasheet will look something like the one in the link below, giving properties in a variety of situations, and the properties when two surfaces are bonded. Once, I saw this material here used, and lap sheer on abraded acid etched aluminum should have been 4,800 pounds per square inch. However, some assemblies were failing, and a simple tug would cause them to come apart. It turned out that folks who had cutting fluids, grease, skin oil, and WD-40 on their fingers were handling the surfaces to be bonded. The surfaces had isopropyl alcohol wipe right before bonding. Once proper handling was accomplished so the materials were not getting on the surfaces, and the person doing the cleaning learned how to properly wipe up invisible residue on the surface, instead of just smearing it around with an isopropyl alcohol saturated chem-wipe, the parts had no problems meeting the specifications. Due to the environment where the parts were epoxied, a more aggressive solvent was later used, to help assure the parts were clean before bonding.
http://tds.loctite.com/tds5/docs/HYSAE-120HP-EN.pdf

Loctite has a general catalog that has various materials available, suggestions, and applications charts. The epoxy materials can be found on page 20:
http://www.loctite.com/int_henkel/l...FullCatalog.pdf

As far as epoxies are concerned, there an innumerable number of formulations that are tailored to meet different engineering needs.

Even 3M offers a number of varieties of just the DP-460. Here is the datasheet for the low outgassing version:
http://multimedia.mmm.com/mws/media...66yXcCOrrrr Q-

Of note, the cured Tg point (glass transition temperature- where the adhesive becomes soft and rubbery), actually varies depending on the curing method and temperature. This is pretty much true for most epoxies. On page 2, you will note that the Tg point will move from 45C to 74C just from different curing temperatures. The Tg point is important, as it is at that point the epoxy will start expanding rapidly, which can lead to CTE mismatch failures between the epoxy and the substrate (which is also affected by bond line thickness and surface prep), and lead to adhesion failures.

I have seen DP-460 fail routinely at my last company, in a certain rare earth motor assembly. Yet, they had been using it for years in many other areas without a problem. Their process was fine, and the 3M folks even came in. The final fix for the failure was to utilize a primer on the surfaces before epoxy application, and to bake the assembly during cure, to raise the bond strength and the Tg point. We called 3M to let them know what the solution turned out to be. Often, the devil is in the details.

The 460NS epoxy datasheet is found here, at the bottom of page 3, note how they use a very aggressive solvent MEK for surface prep, no pussyfooting around there...:
http://multimedia.mmm.com/mws/media...66yvWCOrrrr Q-

A link to 3M's 20 epoxies:
http://products3.3m.com/catalog/ca/...ler/output_html

A link some exotic epoxies from AIT, such as diamond loaded (they also offer lots of lower cost thermal gels and thermal epoxies):
Diamond filled epoxy

"Low-cost" silver filled gel that blows away Arctic Silver (transfers heat 2.5x better- 17.2 W/m-慢 vs. AS @ 7.5 W/m-慢 )

"Other materials, Thermal Gap Fillers, Thermal Phase Change, Thermal Greases, Thermal Gels, In-Situ Thermal Attach Adhesives, etc...

Low cost diamond loaded thermal pads, 10-20x thermal transfer higher than copper, also works as awesome heatspreader to take advantage of surface area gain for thermal transfer:
Diamond Heatspreaders/Insulators/Thermal Pads

IMHO, there is no automagical single epoxy. It is a complex goo that is affected by many different things, and it is best to select the material you really need (selecting the properties you really want) for the application at hand.

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