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Epoxy/Denatured Alcohol mixing question

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Old 07-27-2018, 11:34 AM
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the Wasp
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Default Epoxy/Denatured Alcohol mixing question

I am just wondering if you guys have ever noticed when mixing Epoxy with Denatured Alcohol that the epoxy hardens quicker than normal ?

(Devcon 2 Ton Epxoy)

Jim
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Old 07-27-2018, 11:57 AM
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Steve Collins
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I have not. In fact, many of the times I have tried to thin epoxy it cures but never really hardens. It stays rubbery. Far better to use an epoxy that is already thin such as the Z-poxy type. I can also highly recommend the WEST system epoxies.

An alternative to using a thin epoxy or thinning out a thicker epoxy is to use heat like from a Monokote style heat gun. Use that on a small cup of already mixed epoxy and it will get to almost the consistency of water but you have to brush it on quickly because the heat definitely will make it cure much, much faster.
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Old 07-27-2018, 05:20 PM
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Originally Posted by Steve Collins View Post
I have not. In fact, many of the times I have tried to thin epoxy it cures but never really hardens. It stays rubbery.
hmmm, if you go back a few pages to one of my posts you will see a few guys recommended Denatured Alcohol, and I have read many times where by others have used it. in the passed I always used 99% Rubbing Alcohol but now it's hard to find here,,
I have seen epoxy rubberize before so I know what you are talking about, I have also seen it (when mixed with Denatured Alcohol) to just take longer to fully cure than normal..

I have bought West System epoxies way back in 97 for a full size V-Drive boat, good stuff, I'm betting it even better today

Jim
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Old 07-27-2018, 05:51 PM
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I have noticed a very fast cure time to 30- Minute Epoxy when I added milled fiberglass to the mix!
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Old 07-27-2018, 06:34 PM
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Originally Posted by tailskid View Post
I have noticed a very fast cure time to 30- Minute Epoxy when I added milled fiberglass to the mix!
wow, thank you for answering, I just about always use Milled Fiberglass when I use epoxy (West Systems #403), always have so I can't say that I have noticed that (I'm not saying it doesn't).. but I am now thinking that when adding a thinner the epoxy natural mixes better, resulting in a quicker cure time,,, now add the fact that I include the milled fiberglass

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Old 07-31-2018, 08:05 PM
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I use BobSmithIndustries 30min epoxy and denatured alcohol, usually thinned about 50/50. For me it takes a bit longer for the epoxy to fully cure, then if I just use straight epoxy. When it does cure and fully dry, it's rock hard. There's no "rubbery" about it. When I mix a batch I have more working time when I add alcohol which is nice for coating/painting it on smoothly. If I want a good finish, I use a good brush, If it's just a firewall I just use a throw-away acid-brush.

Climate plays a big part though with any type of resin like this. I'm in the middle of summer here in Cali, and temps are hitting over 100 degrees here in the valley, and everything cures faster no matter how you slice it. I do my work out in the shop before the afternoon heat hits me, but yeah.. some days it hovers around 100 in my shop. No problem with anything curing/drying here... and everything cures fast too.

If I'm using just straight 30min epoxy in the heat like that, I only have about maybe 17-18 minutes of good work time before it starts going off... Very doable, and I actually love using epoxies in this environment for that reason. I use 5min very rarely in this heat...work time with that is maybe 3 minutes. Fine for a quickie, but I'm never in any hurry anyway.
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Old 08-01-2018, 09:39 AM
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thanks for the reply.. I have noticed my epoxy a bit rubbery before yet it's surface is hard, but after a few days it cures solid

Jim
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Old 08-01-2018, 07:05 PM
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Since I use West Systems and it says right on their website not to mix in any solvents, I won't. What I do mix in is their 404 silica and have found that part of the reason it cures "faster" is the added time it takes to actually mix it to get the silica evenly blended in
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Old 08-08-2018, 12:32 PM
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I will thin my laminating epoxy depending on the job at hand but never more than 10% .The pictured airplane, when laying up the fuselage had the epoxy thinned and when glassing the wings and stabs as well. The fuselage layup is 1.4oz surface cloth followed by a layer of 3.6oz cloth, 1/32 contest balsa and a final layer of 3.6oz. Very light layup. The IPA used will slow pot life and cure time.
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Old 09-02-2018, 03:46 PM
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My understanding is thinning with alcohol will weaken the epoxy bond. While I've never seen this myself I've heard enough people swear by it to keep it in mind.

Rubbery epoxy suggests it wasn't mixed as thoroughly as it needs to be. I've seen this happen when adding the alcohol before the epoxy is mixed. Mix the epoxy first before adding the alcohol.

As a rule I no longer thin with alcohol. If I need thinner epoxy, I'll go out and find it.
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Old 09-02-2018, 05:20 PM
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I will thin epoxy with denatured alcohol ONLY when I am applying light (3/4 oz) cloth over balsa. In this thin layer I feel the alcohol has enough time to evaporate before the epoxy gells and trap any solvent in the mix.

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Old 09-02-2018, 06:42 PM
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Ken, this sounds like it would be a great topic for my Facebook composites page. I am working on a segment now that will be dealing with adding different fillers to laminating resin for different jobs. Once that is done I can document making two identical layups with a core material, one with thinned resin and the other without. After a 48 hour cure do some structural tests.
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Old 09-03-2018, 05:09 PM
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Originally Posted by speedracerntrixie View Post
Ken, this sounds like it would be a great topic for my Facebook composites page. I am working on a segment now that will be dealing with adding different fillers to laminating resin for different jobs. Once that is done I can document making two identical layups with a core material, one with thinned resin and the other without. After a 48 hour cure do some structural tests.
This is a highly debated subject. Sounds like a great idea for your FB page!!!

Ken
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Old 10-18-2018, 03:45 AM
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I was told many years ago by a manufacturer to only thin epoxy with styrene but have never tried it.
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Old 10-18-2018, 10:32 AM
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Originally Posted by Faux Fisherman View Post
I was told many years ago by a manufacturer to only thin epoxy with styrene but have never tried it.

Styrene Monomer is the thinner for polyester resin not Epoxy
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Old 10-18-2018, 01:04 PM
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good point to clarify between polyester resin and true epoxy...... many people aren't aware of the difference.
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