Epoxy Comparisons and Technical Data Sheets

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Well-Known Member
Oct 13, 2014
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Pasco, WA
I get tired of reading posts about whose epoxy is better so I went out and gathered so common epoxy technical data sheets from our manufacturers and vendors, my opinion after comparing them is that none have a definitive edge over the others but each does have some characteristics that may make them better for a certain application. I am not sure why the US Composites have a range for PSI's but it may be due to different curing techniques. All epoxies I believe are considered to be "neat" as tested (only Aeropoxy gave test data with reinforcements like FG, CF, and Kevlar and that data is not listed on the table below). For the US Composites 150 the lower rated of the two hardeners was chosen, an inquiry is in the US Composites for clarification on which hardener is the correct one for the 3:1 ratio, the other could be the 1:1 ratio.

Epoxy ComparisonsCropped.jpg

Edit: 1/20/2019
Proline Epoxy

Tensile Strenth psi 9,500
Compression Strength psi 15,000
Flexural Strength psi 16,000
Shore D at 73F 90
Shore D at 350F 78

Proline 4500 is right along similar lines as the Aeropoxy PR2032, both of which are gel consistencies iirc.

Information taken directly from the Technical Data Sheets as provided by the manufacturers/vendors. This information is compiled in an effort to give as direct a comparison as possible for all the epoxies that we as rocketry hobbyists tend to use.

View attachment 311983
View attachment 150 Thick Resin.pdf
View attachment AEROPOXY ES6209 Bulletin.pdf
View attachment AEROPOXY PR2032 Bulletin w-4 Hardeners 24Jun08.pdf
View attachment JB-Weld-Technical-Datasheet.pdf
View attachment 311987
View attachment TDS 105_205.pdf
View attachment TDS 105_206.pdf
View attachment TDS 105_209.pdf

The West Systems Epoxies are the TDS files, Glenmarc RocketPoxy is G5000, and the others are Aeropoxy and US Composites.

Edit: 1/19/2019 The original table in this post was corrupted by the new XenForo update when TRF upgraded, so the only thing that changed was removal of the corrupted text and a JPG of the original table was inserted. Proline is not on the table as I did not have data available for it, if anyone has a Technical Data Sheet for Proline 4500 please share it.
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It doesn't appear right on my iPad either, but I'm not sure if it's Tapatalk or the iPad. In any case, thank you very much for assembling the data!!

Edit: It's Tapatalk; looking at it in Webview the table looks great.
Steve Shannon
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Some of the ND's may actually be on the data sheets just under another name, the terms used are not ones that I am familiar since material science is a class I never took.
Just got an email from US Composites, with the exception of the 1:1 hardener the 635 and 150 epoxies use the same hardeners (2:1, 3:1, 4:1). Only the 150 epoxy uses the 1:1 hardener.
Getting ready to update this thread in the next couple of days to a format the new forum software will use. The topic of the common epoxies we use in hobby rocketry has come up again and this comparison thread shows as much as possible how the various common epoxies vary.
Original post fixed so table is visible again, afaik the PDF files are still downloadable from the OP.

John, I agree with you that its hard to know how applicable the numbers are in practical terms from the data sheets, however it does allow some form of comparison and should be taken with a grain of salt. From my experience with West, Aeropoxy and US Composites, those three brands are close enough in form, function, and useage that they are interchangeable in my opinion. Of course almost none of us use these epoxies "neat" except for laminating and occasionally the structural epoxy applications (even the structural adhesive epoxies are pretty thin) and as soon as we start adding fillers and thickeners the properties change greatly.
I guess I always figured the trick to epoxy is using the correct one for the correct job!! For example I use West Systems G-flex for most structural jobs because it is slightly flexible for boats and thus can take a good shock force. Then Miller Stephenson 828 is a much thicker epoxy that is great with fillers for fillets. And to plasticize fins for example, a very thin clear cast epoxy works great.. It is almost like an optical epoxy. I don't use 5-minute types for anything that I want strong as it just doesn't work that great for those jobs but can be great for things like attaching rail button backings....

The other trick is don't get any epoxy on you! Aminels, bla.
Epoxy choice is definitely important, the only Epoxies listed in the first post were ones that repeatedly come up in " what epoxy is best" type threads. I had no data for BSI epoxies and they are probably more used than all the others combined and based on BSI cured characteristics probably perform closer to JB Weld (excluding the heat resistance of JBW) than Rocketpoxy.
Still a great table! Then there is surface prep that is probably as important...
Cool table! One correction (it's ES6209, not ES6029), and suggestion for a few more useful columns:
  • viscosity (varies drastically among the ones listed)
  • pot life
  • cure time
Cool table! One correction (it's ES6209, not ES6029), and suggestion for a few more useful columns:
  • viscosity (varies drastically among the ones listed)
  • pot life
  • cure time
At this point no new columns will be added, your suggestion are good ones but making tables like that one is a P.I.T.A. with the forum software. Due to the age of the original post I had to request permission to edit the OP.
With the fillers we tend to add to our epoxies ( with the exception of Rocketpoxy) I would not be surprised to see the 3 highest in tensile strength once amended are actually closer to Rocketpoxy.
I'm curious why you say "with the fillers we tend to add to our epoxies". I have never added fillers to BSI or Aeropoxy. Fillers are necessary for thickening West System for bonding, but not all. Note that Aeropoxy has a different formulation for laminating and bonding. As you can see on my page, the laminating formulation (PR2032) is weaker for bonding than the bonding formulation (ES6209).
Do you not ocassionally add Cabosil, milled glass or carbon? These are the common fillers I am referring to, some epoxies like Rocketpoxy may already contain cabosil or some other filler ( its propritary info most likely). Fillers are not always needed or desired but sometimes they are necessary. Yes I am aware that Aeropoxy has several different formulations and each has a different purpose. John I respect your advice and have read your pages multiple times and regulary point people to them as sources of information. The point of this thread is simply to put information out there that is commonly available. IMO the arguements about who's epoxies is better are pointless we each find what works for us, you from most of your videos and information I have read you have chosen Aeropoxy products as your preference. US Composites 150 is my adhesive of choice and US Composites 635 is my laminating epoxy of choice as they are easy to use and I have yet to have either fail on me, nor have I had the Aeropoxy, West, or System 3 epoxies fail. Rocketpoxy and Proline I have no experience with. BSI epoxies I have been using for many years, and I grew up around my fathers fiberglass shop so I know my way around molds, mold prep and construction, MEK catalyzed polyester resins, fabric based layups and chopper gun spray on techniques, vacumn bagging was something we didnt do a lot of but I am learning now.

I would love to see more of the same type of tests you had done before with all of the epoxies we see being used now, but without that testing technical data will have to do.
I was under the impression that one should never add anything to RocketPoxy?

He’s talking about everything other than Rocketpoxy.

I do exactly what you’re talking about. I use Aeropoxy laminating epoxy for everything on larger rockets and I add specific amendments depending on what I’m doing. It’s pretty much the only thing I’ve used for years, although the long cure time is sometimes great and sometimes holds up progress.
For external fillets I’ll use silica. For cosmetic touch ups I have used microballoons. For internal fillets I’ll use either silica or chopped fibers. Whenever I’m bonding something I paint the joints with the unmodified epoxy first under the assumption that I’ll get better adhesion and penetration.
I keep meaning to try some of the structural Aeropoxy, but haven’t gotten around to buying any. And I’ve been given a couple gallons of West Systems epoxy and fast and slow hardeners so I might never get around to it. I’ll add the same modifications to the WSE.
Do you not ocassionally add Cabosil, milled glass or carbon?
No, not for bonding; ES6209 is already the right thickness for me.

IMO the arguements about who's epoxies is better are pointless
Very much agree. I hope I'm not coming off that way. I just want to make sure people don't get too simple a view.

I would love to see more of the same type of tests you had done before with all of the epoxies we see being used now, but without that testing technical data will have to do.
Yeah, I don't know of anyone else who has testing equipment available. Maybe someone will show up and we can do another test of that kind.
1) The structural numbers in the table will only apply if the temperature is below the Glass Transition Temperature, Tg, which I believe is being labeled as Deflection Temp in the table.

2) Aerospace epoxy systems have their structural properties listed by the manufacturer under the assumption that the proper cure and post-cure heat treat cycle has been applied. Otherwise, with one exception, the Tg is lower than the listed value as are the other physical properties.

3) That exception is MGS epoxy. It has the highest physical properties of conventional laminating resins when not subject to post cure heat treat, and better when it has been.

4) Unfortunately, West Systems won't heat treat. WYSIWYG.

Heat treat epoxy?? Really never heard of such a thing!! What Mach speed is needed:)
For example I use West Systems G-flex for most structural jobs because it is slightly flexible for boats and thus can take a good shock force.

Interestingly one of the few industries that measures and publishes impact strength (or as you say above shock force) for their epoxies is golf. There have been some fine epoxies in use in that hobby for decades. Another help in shock/impact is adding/using the right matrix. A good general article on matrix characteristics is here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5607334/.
Can we add AeroMarine 300/21 and 400/21 to the list? They have data sheets on the website and they perform better than most. Survived a high thrust M-motor.
Go ahead and attach the Tech sheets to your post here and I will add them as I can. However the list is primarily Common epoxies that seem to come up in nearly every "which epoxy is best thread".
Does anyone know how to covert Barcol Hardness to Shore D hardness, so the epoxies can be directly compared ?

Dave F.
According to Wikipedia (not the best source I am sure) a Barcol 60B is equivalent to a Shore 80D, IMO hardness is also going to affect how brittle the epoxy is, a hard epoxy is going to break before bending much. According to other sources I have seen there are no reliable ways to directly compare the two hardness standards, though there is a ASTM for doing so in metal materials, but both Shore D and Barcol are used primarily for relatively soft materials like rubber and rigid plastics, though iirc the Barcol test was developed originally to spot suspect/counterfeit rivets in aircraft manufacture.
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