Room temp cure laminating epoxy

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Dustin Lobner

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Hi everyone,

I need to do some fiberglassing in my basement where it's a solid 68*F. For structural epoxy I use T-88 for a wide variety of reasons...one of which is that it'll cure up as reduced temps.

For laminating, all of used is Aeropoxy, which claims to be RT cure but I've never had it work out that way, I can only laminate when it's like 80*F outside...and I live in Wisconsin.

Does anyone know of an epoxy that'll cure at basement temps (just a bit below RT really). Bonus points for clarity after cure, as this will be going on colored fiberglass sock.

Thanks!
 

Budro0

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I'd look at West 105/206. It cures pretty clear and I've used it down in the lower 60s with no issues. I did have to invest in a small heater to keep my garage above 50 in the winter though.
 

Dustin Lobner

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Has anyone tried the 207 "special clear" hardener? I'd be OK with a longer cure time if it looks "nicer". I'm using dyed fiberglass sock and would like that color to come through as well as possible.
 

mtnmanak

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I would second the vote for West System for cooler temps. It is why I moved away from Aeropoxy for laminating. Aeropoxy 2032 takes forever to cure, even if you keep it hot. At room temperature, AP 2032 could take up to a week to fully cure. West cures quickly.

I have tried 207 and it cures very similarly to the 206 "slow" hardener. It doesn't have good structural properties, but it does give you a beautiful finish. The 206 hardener does have a slightly amber color, but it does dry fairly clear. If you plan to use the hardener for more than just laminating, 206 may be a better investment if you only buy one and can live with the finish not being glass clear. If you can buy both, then no worries. Note, though, the mix ratio is different for 207 vs. 205/206. If you use their mini pumps, as long as you put the correct one in the correct can, you are good. I do love their pumps - they make the whole thing super easy. At room temp, it is pretty useable after curing overnight, with full cure by end of the next day.
 

Antares JS

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I also can testify that West System still cures well when it's a bit chilly.

For what it's worth, West System also makes black, white, and gray pigment for their epoxy. If your pre-colored fiberglass parts happen to be one of those colors, you might consider using the pigment instead of looking for a glass-clear finish. I am currently using the black pigment for the fin fillets on a Rocketman Space Shot.
 

Dustin Lobner

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Thanks for the replies everyone!

The color for this would be fire engine red, so pigmented isn't an option.

I have tried 207 and it cures very similarly to the 206 "slow" hardener. It doesn't have good structural properties, but it does give you a beautiful finish.
By structural, I assume you're saying if I made fillets or whatever with it? This would be laminating only, I use T-88 on anything structural, so that's not really an issue here.
 

ECayemberg

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West 105/206 has always been tops; 207 works fine as well...I've used both without issue. US Composites 635 as a more affordable alternative at the expense of slightly lower performance (in my opinion). Like you, Dustin, I could never get Aeropoxy laminating epoxy to set up as desired in Wisconsin (even in my moderate temperature basement). I do have a curing oven...with a little heat its great, but the added effort was never worth it to me.
 

tfish

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I put some of my epoxies in an ice bath before and after mixing...to prolong their working times. This thickens the epoxy up some and makes it a tad harder to use. They set up just fine. My shop's not always warm..some times I use a little electric space heater to warm up freshly laid up parts..

I used to use T-88. I would even thin it down with denatured alcohol to do layups with it. I found it to be pricey.. I've since switched over to Raka epoxy. The 900 HP resin with the 631 hardner..no real specs sheets on it..

Tony
 

Budro0

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Thanks for the replies everyone!

The color for this would be fire engine red, so pigmented isn't an option.



By structural, I assume you're saying if I made fillets or whatever with it? This would be laminating only, I use T-88 on anything structural, so that's not really an issue here.
I bought a cheap box of assorted pigment from amazon to dye West 105/206 - it's not perfect, but would get a red color to match your glass. And for $15, not a huge investment.
 

boatgeek

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I am a fan of Silvertip by System 3, the same folks that make T-88. The medium or fast will easily cure at 68F, but check the manufacturer's cure times. I like to have 45 minutes of working time at least for laminating. The big bonus for Silvertip for me is that bubbles seem to migrate to the surface and pop easier than other epoxies I've used. The 2:1 ratio also makes it a bit easier to make small batches.

[edit] Silvertip is also quite clear, with a slight yellow cast.
 
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mtnmanak

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By structural, I assume you're saying if I made fillets or whatever with it? This would be laminating only, I use T-88 on anything structural, so that's not really an issue here.
Exactly - 207 would work and probably is fine for structural use and it's rated strength is very close to that of 206. The biggest difference, however, is the 207 has a pretty significantly lower Tg temperature. That won't matter much for a laminating job, but you probably don't want your structural joints getting rubbery when the temperature gets high. On the other hand, a lower Tg may be good for an external fillet that would be subject to a lot of force upon take off and landing. Temps above the Tg temperature won't melt the epoxy, but they do get softer as the temp goes above Tg. A little flexibility in your external fillets may not be a bad thing.
 

Steve Shannon

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Hi everyone,

I need to do some fiberglassing in my basement where it's a solid 68*F. For structural epoxy I use T-88 for a wide variety of reasons...one of which is that it'll cure up as reduced temps.

For laminating, all of used is Aeropoxy, which claims to be RT cure but I've never had it work out that way, I can only laminate when it's like 80*F outside...and I live in Wisconsin.

Does anyone know of an epoxy that'll cure at basement temps (just a bit below RT really). Bonus points for clarity after cure, as this will be going on colored fiberglass sock.

Thanks!
Aeropoxy works well for me in Montana. It takes a few days to reach full cure but that’s okay with me.
If I wanted clear I would look for bar top epoxy.
 

Dustin Lobner

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Aeropoxy works well for me in Montana. It takes a few days to reach full cure but that’s okay with me.
If I wanted clear I would look for bar top epoxy.
I've had aeropoxy sit in my basement for a week and still be tacky enough to use as a lint roller...maybe my basement is colder than 68 or whatever, more like 64. Set the part out in the sun for a day and it hardened up nicely...but that only works in July, lol.
 

G_T

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You might want to start by determining what structural properties you want after it is cured. What is the minimum Tg you can get away with for instance? Are you making a structural layup, or a cosmetic layup?

Your basement temperatures are not good for the job. Even a primitive warming box can solve that problem.
 

Dustin Lobner

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You might want to start by determining what structural properties you want after it is cured. What is the minimum Tg you can get away with for instance? Are you making a structural layup, or a cosmetic layup?

Your basement temperatures are not good for the job. Even a primitive warming box can solve that problem.
Nothing too special. 3D printed fincan/mmt, so it isn't going to have any direct contact with a motor or anything, so Tg is basically irrelevant. Purpose is both cosmetic and structural, as this will eventually go to about mach 1.3 on an L1000.

As far as temps go, I was told by a guy with a PhD in Adhesives (so, Chem E or whatever) that a "typical" epoxy doubles in cure rate every 10-15°C that it warms up. This is why there are such a thing as one part epoxies that are elevated temp cures...they're two part epoxies, mixed at the factory, but the reaction isn't fast enough to be meaningful till 300-400°F or whatever. If the epoxy is heavily exothermic on curing, this is also what causes it to run away and cure super fast if it gets too hot. Obviously there are a ton of caveats with all of that, but it's a good baseline. That's once you get over an initial threshold value where the reaction can happen at all.

What I've found with Aeropoxy is that with cooler air, it cures up super slowly or not at all, at 80°F it's "about right", and then at 90°F it cures up in like 20 minutes and is a lot darker. There's a very narrow band where it's OK. Also noticed that it gets really dark if it exotherms hard and cures too quickly (most epoxies do this). So, if West Systems is able to cure at lower temps...I don't really care if it takes a day or two, provided it actually cures. The difference in time between 60°F and 70°F doesn't bother me much, but it's reliably getting over the threshold where it starts to cure at all that is important.
 

mtnmanak

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So, if West Systems is able to cure at lower temps...I don't really care if it takes a day or two, provided it actually cures.
Give West a shot, I think you will be happy with it. I still use Aeropoxy 6209 for a lot of structural bonds, but for laminating, West has really been great.
 

Sandy H.

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US Composites. http://www.uscomposites.com/epoxy.html
I've been using their epoxy systems for 12+ years. Select a cure time with choice of 4 hardeners depending on ambient temperature.
I also have had good luck with USComposites for laminating and faring type features. The only time it didn't work for me was complete user error, so can't blame the product.

Sandy.
 

catman001

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Hi Dustin. A couple of things to keep in mind. First is that some epoxys have a yellow tint to start with, if they start yellow they will cure with a yellow tint. Second thing is that all epoxys will yellow over time with exposure to UV radiation (think sunlight).

The first thing is easy, just start with a clear epoxy. The second item is a bit more difficult. There are however some epoxys with UV inhibitors in them.

I am user of West epoxys, and have been very happy with them. I think the 207 hardner will meet all of your needs.

1. It is crystal clear
2. It can be used down to 60 degrees F
3. It has UV inhibitors

http://www.westsystem.com/207-special-clear-hardener/
 

TXWalker

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I've been using epoxies for years on various boat building projects. Of all the different epoxies I've tried I like WestSystem products the best for consistent results. If you are looking for low temp cure try the 205 Fast cure hardener. It will cure down to about 40F. I used this for a winter boat building project in an unheated garage. I never had an issue with it curing. It will cure to a slightly more amber color than the 207 slow cure harder. Be careful when working with 205 above 72F, I was working with a dixie cup full of resin that auto ignited on me. A very strong exothermic reaction, it started to foam, smoke and eventually caught fire.

For a crystal clear top coat finish I used MAS https://masepoxies.com

Any epoxy will yellow over time with exposure to UV light. WestSystems sells graphite powder or aluminum powder as a UV blocker. If black or gray is not your thing you can try adding a polyester resin pigment. In my experience with white pigment it will yellow over time left out in direct sunlight. For my wooden boat project I used a high quality spar varnish over the MAS/glass layer. You can can't see the glass cloth over the mahogany unless you get right up to it.

For my current carbon fiber composite rockets I'm using 207 harder in the unheated garage. It will normally set up enough overnight that I can bring the parts inside to finish curing. I can't see the amber color against the black carbon fiber. I plan to spray clear coat as the UV blocker.
 

Dustin Lobner

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For a thread about "which epoxy", this has been fantastically informative. Thanks everyone for sharing your thoughts!
 

rharshberger

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+1 again for US Composites 635 laminating and 150 structural adhesive epoxies, easy to use and easy to get good results with.
 

blackjack2564

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My inside out....curing oven...lol

I put my hairdryers snout in the front end of fincan or payload tube.turn to low and let it run just an hour or so ...your work will be hard as a rock. of course tube must be large enough to fit...or use one of those reducer thingies on the dryer.

garage was unheated and 45 degrees out

Ps u must leave one end open or tube will get so hot the thermal safety will shut down the hairdryer...if big tube 5-6 -7.5in u can partially block
 

Dustin Lobner

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My inside out....curing oven...lol

I put my hairdryers snout in the front end of fincan or payload tube.turn to low and let it run just an hour or so ...your work will be hard as a rock. of course tube must be large enough to fit...or use one of those reducer thingies on the dryer.

garage was unheated and 45 degrees out

Ps u must leave one end open or tube will get so hot the thermal safety will shut down the hairdryer...if big tube 5-6 -7.5in u can partially block
I've done that too. Want to prevent having to do that if possible...if it gets hot enough, it'll "cook off" which will make it tan. Trying to keep it as clear as possible.
 

G_T

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I've run cure on some epoxy systems pretty hot without any cooking off issue. If you have too much epoxy in your fabric or a thick layup, that might be different. Lightbulbs can be another source for heat. Ceramic heaters. Portable oil filled radiator heaters. Electric blankets. Heat pads. Black trash bags and sunlight. Get creative!

Bulk mixed epoxy will generally cook off. So mix it then spread out thin on a plate. You'll have more working time.

Gerald
 

REK

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I’ve used this one with great success. It has a decent pot life of 40 minutes, Tg up to 180F, UV stable and will cure in cold temperatures.

 
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