Humidity & Temperature during epoxy curing

[_andi_]

Hi,

so the datasheet says less than 70% rel humidity and 20-25C optimal temperature and 18C/65F minmal temperature, demouldable after 36h.

I'm doing Epoxy/Fibreglass work on the bottom of my boat which is on a meadow by a river, never ever will this window of temperature/humidity occur for 36h straight in central europe. Everything has been fine so far. But the nights get more nippy and humid.

Now I'm wondering with what I can get away with. I'm contemplating something like starting late in the morning after all morning dew dried out, apply a couple of layers wet-in-wet until like four in the afternoon, stick on peel ply and repeat the next day.

Has anyone some guidance/experience on this? The total cure time doesn't really matter, I won't splash the boat until next year but I'm concerned about the bonding between layers.

Thanks, Andi

[coopec43]

Can't you cover your epoxy work with some thick heat insulating material like old scrap doonas?


Maybe you should be looking at a different quick setting epoxy?


Catalyst Epoxy Hardener speeds up the curing process of normal curing hardener down to 2Hours time. It is Part B of Epoxy Blend to be used with most Part A Epoxy products such as Premium Tinted Epoxy and Ultra Clear Epoxy.

https://shimi.com.au/wp-content/uplo...rdener-V01.pdf

I AM NO EXPERT THOUGH.(my experience is with polyester resins) I think I'd get an expert opinion.

[SailingHarmonie]

Originally Posted by coopec43

I AM NO EXPERT THOUGH.(my experience is with polyester resins) I think I'd get an expert opinion.

Doesn't he already have an expert opinion in the form of the written instructions?

It's a common question on here: "Can I ignore the instructions?"

And the answers given are always the same: "Yes", "No", and "Maybe"

Working in an uncontrolled environment with epoxy is difficult.It is inherently temperature sensitive, some systems more than others. Lower than recommended temperatures can simply slow cure times, (annoying) or stop curing before it finishes, and it never goes all the way. (disaster)

If you want answers from people with experience pushing limits, you have to tell us exactly what specific product you are using and what you are using it for.

[Jammer]

Originally Posted by _andi_

so the datasheet says less than 70% rel humidity and 20-25C optimal temperature and 18C/65F minmal temperature, demouldable after 36h.
[...]
Now I'm wondering with what I can get away with. I'm contemplating something like starting late in the morning after all morning dew dried out, apply a couple of layers wet-in-wet until like four in the afternoon, stick on peel ply and repeat the next day.

I'm in the Minneapolis area and use epoxy often in boatbuilding and repair. It's cold here.



You're going to double the cure time for every 10 degrees C in lower temperature. Humidity has little effect as long as the environment is non-condensing. I've never tried to use epoxy in temperatures below 5C.


If you have a choice of hardeners with the epoxy system you're using, you would of course want to use the fastest one available.

[coopec43]

Originally Posted by SailingHarmonie

Doesn't he already have an expert opinion in the form of the written instructions?

It's a common question on here: "Can I ignore the instructions?"

And the answers given are always the same: "Yes", "No", and "Maybe"

Working in an uncontrolled environment with epoxy is difficult.It is inherently temperature sensitive, some systems more than others. Lower than recommended temperatures can simply slow cure times, (annoying) or stop curing before it finishes, and it never goes all the way. (disaster)

If you want answers from people with experience pushing limits, you have to tell us exactly what specific product you are using and what you are using it for.

Maybe he is using the wrong epoxy for his environment!
There are different variations to suit different conditions.

For example when I painted my yacht I had a choice of three different hardeners- an ultra fast (for spray painting), one for brush painting in normal temperatures and another hardener for cold weather.

I've used plenty of epoxy on my yacht but only in "normal" temperatures.

To help expedite the cure, use a fast speed hardener, if available for the epoxy system you’re using. TotalBoat High Performance Epoxy Fast Kit provides the fastest cure and shortest working time at room temperature, or achieves an overnight cure in low temperatures (minimum 55°F). To help the epoxy cure faster, you can also warm the surface before applying epoxy, and warm the air in your workshop.
https://www.totalboat.com/blogs/tota...n-cold-weather

[coopec43]

Originally Posted by Jammer

I'm in the Minneapolis area and use epoxy often in boatbuilding and repair. It's cold here.



You're going to double the cure time for every 10 degrees C in lower temperature. Humidity has little effect as long as the environment is non-condensing. I've never tried to use epoxy in temperatures below 5C.


If you have a choice of hardeners with the epoxy system you're using, you would of course want to use the fastest one available.

+1 (nice to read a comment from someone who knows what he is talking about!)

[GordMay]

“Epoxy Problem Solver (FAQ)” ~ WEST SYSTEM
➥ https://www.westsystem.com/instructi...em-solver-faq/

“3. Clear coating turned cloudy
Moisture from condensation or very humid conditions reacts with components in the uncured epoxy hardener.
Apply moderate heat to partially cured epoxy coating to remove moisture and complete cure. See Out-Gassing caution in 'Epoxy Chemistry'*.
Use 207 Special Clear Hardener® for clear coating applications and for bonding thin veneers where epoxy may bleed through to the surface ...”

* “Epoxy Chemistry” ➥ https://www.westsystem.com/instructi...oxy-chemistry/

“How Does Humidity Affect Curing Epoxy?” ~ by Roderick Kabel [WiseBond Epoxy]
➥ https://www.wisebond.com/blogs/epoxy...t-curing-epoxy

“Frequently Asked Questions About Epoxy” ~ by WiseBond Epoxy
➥ https://www.wisebond.com/pages/faq

“Understanding the Effect of Humidity on Epoxy” ~ by Just Resin Pty Ltd
➥ https://www.justresin.com.au/single-...idity-on-epoxy

[Fore and Aft]

Andi the only trouble with fast hardener is you have to be on top of your game glassing. So if you're doing the underside of your boat, the fiberglass needs to be pre cut, wet out, applied etc and no hold ups.
Fast or medium hardener would be my choice. What is the repair you are undertaking?
Cheers

[Chotu]

you are absolutely fine. not having condensation is the important part. You don’t want a wet surface.

what will happen is if you are below the threshold for the curing, it will just stop or slow down. This can be annoying and frustrating and if you don’t have it properly supported and kept in place it can wreck the job.

however, once temperatures pick up again a bit, the curing will continue. This is how they make pre-preg refrigerated composite components. It’s just regular epoxy in the refrigerator. It never hardens. Yours will reach curing temperature from time to time, hopefully, and if it doesn’t, just throw a little heat on it in the form of a heat lamp or kerosene heater

there is nothing detrimental about being too cold or too humid as long as the surface is not wet and as long as you can get it warm enough occasionally to make it cure.

source? I have mixed enough epoxy to no longer be able to use it anymore. I’m in the hundreds of gallons category

[Fore and Aft]

Andi the worst I have had is in the morning there's a film of white on top of the fiberglass. I quick wipe with the grinder and its gone. That only ever happens on outside horizontal surfaces. I have fiberglassed in sheds when you can see your breath in the air. Never had a problem.
Cheers

[PippaB]

It's the internet, so you will get so many opinions that you can choose whichever one suits you. Given the OP's statement of a multi-day lamination I would select the slowest hardener that works for all the other conditions. Needs to cure enough that it does not fall off upside down work, needs to work with the minimum overnight temperature, etc. Depending on how retarded the cure the next day's lamination might then achieve a partial chemical bond - but that is all in the details we don't have.

Once the lamination is complete I would tape a tarp from the sheer (or waterline if only working on the bottom) to the ground, and use a forced air electric heater to raise the air temperature around the hull to a nice curing temperature, and let the boat soak in that until the lowest lamination level has reached that temperature. For areas where gravity is your friend you can also just lay an electric blanket on the lamination and let it sit a few hours, then move it around.

You can even use the tarping technique throughout the process if you install it in a way that it is easy to fold away from the work area during the day and let down at night, then you can run either a dehumidifier or a heater each night to keep the hull dry. It sounds like a lot of work, but it really isn't.

Epoxy is a fascinating material; it is both intolerant of mistakes and very forgiving. Most of the room-temperature-cure epoxies with which I have worked will, as Chotu says, finalize their cure. From Gougeon:

Elevate the temperature of partially cured epoxy. Elevating the temperature of the epoxy after initial cure can help to complete the epoxy mixture’s cross-linking and boost the epoxy’s physical properties even after a week at cold temperatures. Elevate the temperature of the epoxy and substrate gradually to avoid thermal shock. Although any temperature elevation will improve cross-linking, try to boost the temperature to 22°C or warmer. The time required for final cure depends on the hardener used and the temperature the epoxy is exposed to. Generally, higher temperatures require shorter cure times. Do not exceed 60°C and do not remove clamps or load the joint until the epoxy has cooled. CAUTION! Heating a porous material may cause air within the material to expand and “out-gas.” Allow the epoxy to reach a partial cure before elevating the temperature. If an epoxy coating applied over the material has not gelled, bubbles from the out-gassing material may show up in the cured coating or glued joint as it warms. In some cases, your shop will naturally warm itself enough to complete the cure during the day, following a cold night. Outdoors, building a plastic tent to trap heat can easily boost the temperature enough for the epoxy to cure. Turning up the thermostat, using radiant heaters, electric heaters or electric blankets are the most common way to control the cure temperature in a shop. It is not necessary to heat the entire structure if you are working on only a small area. Tents of plastic or insulated board are very helpful for confining heat to specific areas and provide greater mobility with a limited heat source, both indoors and outdoors.

[MicHughV]

In the summer, I think the trick is to mix up the epoxy in small manageable batches and give it a go and see what the outcome is. If the first batch goes off correctly, you can continue with the rest, also in small batches. This can be tiresome on a large project, as one has to mix and apply, but one can control the mixing, the cure and final result, without risking a huge amount of epoxy going off faster than you can apply it.

I've also worked epoxy in some real cold weather by simply providing a makeshift cover and a small space heater. As above, mix and apply in small batches.

I've worked mostly with the WEST system, but have also use other brands with equal success.
Epoxy is expensive stuff, so screwing it up is not an option.

[MicHughV]

My last 2c. Most people that have worked with epoxy have found out the hard way that attaining the correct mix ratio is key to the whole thing. Whatever or however you do this, it must be accurate. Not doing this correctly, will result in a batch of epoxy that will never cure properly and trying to remedy this problem after the fact is a frustrating and time consuming experience.

[rognvald]

I never had a problem with West Systems epoxy with a fast/slow hardener option from Lake Michigan to the Tropics.
Rognvald

[Nicholson58]

Originally Posted by _andi_

Hi,

so the datasheet says less than 70% rel humidity and 20-25C optimal temperature and 18C/65F minmal temperature, demouldable after 36h.

I'm doing Epoxy/Fibreglass work on the bottom of my boat which is on a meadow by a river, never ever will this window of temperature/humidity occur for 36h straight in central europe. Everything has been fine so far. But the nights get more nippy and humid.

Now I'm wondering with what I can get away with. I'm contemplating something like starting late in the morning after all morning dew dried out, apply a couple of layers wet-in-wet until like four in the afternoon, stick on peel ply and repeat the next day.

Has anyone some guidance/experience on this? The total cure time doesn't really matter, I won't splash the boat until next year but I'm concerned about the bonding between layers.

Thanks, Andi

As long as the initial application and indication of cure occurs in good conditions you should be OK. I’ve never had problems even including rain once the epoxy begins to gel. One thing you can do to protect a new surface is to cover the repair with polyethylene sheet. This keeps the atmosphere away and additionally prevents slump on vertical or upside down surfaces. Extend the sheet well beyond the wet area and use tape to hold it in place. Smooth the area and work excess resin out. This compresses the mats and air can’t get in.