Using epoxy without hardener?

surferguy001

Seaman
Joined
Feb 12, 2010
Messages
70
im using fiberglass resin to fiberglass a new engine cover 'dog house' that i made out of wood. when i mixed the epoxy with the hardener the working time was not long enough for me. If i dont use as much of the hardener will the final result still be as strong? are there any other effects of this, or does hardener just speed up the process a little bit?
 

Black as

Chief Petty Officer
Joined
Feb 22, 2010
Messages
417
Re: Using epoxy without hardener?

im using fiberglass resin to fiberglass a new engine cover 'dog house' that i made out of wood. when i mixed the epoxy with the hardener the working time was not long enough for me. If i dont use as much of the hardener will the final result still be as strong? are there any other effects of this, or does hardener just speed up the process a little bit?

You should really be following the manufactures instructions on the container.

But yes I have put a little less activator in so I have more time to apply it without any problems, it also depends on what the ambient temperature is as well as the warmer it is the quicker it will go off. I was lucky enough to experience rebuilding a hull with fiberglass around 20 years ago and still see it on the lake today :D
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
Re: Using epoxy without hardener?

Time to find a formula that has a longer working time. It on the labels.
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
Re: Using epoxy without hardener?

Epoxies are very sensitive to the ratio and while it may get hard, it doesn't mean its cured well, resulting poor physical properties and less water resistance. Its best to stay as close as possible to the recommended ratio.
 

Bondo

Moderator
Staff member
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Apr 17, 2002
Messages
70,465
Re: Using epoxy without hardener?

Its best to stay as close as possible to the recommended ratio.

Ayuh,... I mix AT the required ratios,...
If it's kicking off to soon,...
Put your resin bucket into a bigger bucket with Ice surrounding the resin bucket...
That'll S l o w the kick off...

Under catalyzed is just Asking for Trouble,....
 

jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,174
Re: Using epoxy without hardener?

MEasure out 3 smaller batches instead of one big batch, rinse tools in acetone between batch mixes or the third batch will cure like you mixed it with the first one.


...or use a bigger brush.:)
I like to use a 4 inch brush.

Mostly I work with poly, I get about 12 minutes to work it so I just set up a few batches and work fast.

The trick with epoxy is to get it out of the pot, then work time can be up to 45 minutes depending on what you bought.
 

89nissanbassboat

Seaman Apprentice
Joined
Mar 6, 2010
Messages
31
Re: Using epoxy without hardener?

I accidentally put too much hardener in while using a aluminum can for a small spot repair...I used what I needed and set the can down to focus on the repair at hand...just a few seconds after, it started to smoke real bad and melted the can:eek:, filled the shop with a raunchy smell...the epoxy crystallized in a matter of milliseconds...I will never use aluminum to mix epoxy for small repairs again.
 

erikgreen

Captain
Joined
Jan 8, 2007
Messages
3,105
Re: Using epoxy without hardener?

It wasn't the mix that did that. It was the temperature and the can shape.

If you want epoxy to have a slow kick off, put it in a big wide tray or mix a small batch. Always match the part A to part B ratio to what the manufacturer recommends. You can also cool it with ice or keep the stuff in a refrigerator, but that can affect curing too.

If you put in too little or too much hardener, you won't get a proper cure. That's it. It won't explode or cook because of that. If you put in too little hardener you sometimes won't even get the stuff to harden. But if it does harden as ondarvr says it won't be full strength.

Neither will "cooking" (heating) epoxy mixed with too little hardener help things... if you mixed it ok and it's just been too cold to cure sometimes it'll help it harden, but if it's short on hardener all it will do is make it more runny.

Those tricks work for poly resin, not epoxy. Bottom line, mix the stuff at the temp and ratio recommended by the manufacturer. If you don't have enough working time, switch to a different epoxy.

The USComposites stuff I use in the "medium" speed is comparable to West Marine's "slow" speed... it varies from mfgr to mfgr.

Erik
 

timfives

Petty Officer 1st Class
Joined
Jul 30, 2009
Messages
382
Re: Using epoxy without hardener?

im using fiberglass resin to fiberglass a new engine cover 'dog house' that i made out of wood. when i mixed the epoxy with the hardener the working time was not long enough for me. If i dont use as much of the hardener will the final result still be as strong? are there any other effects of this, or does hardener just speed up the process a little bit?

another issue by changing the mixture, is the strength. If you change it drastically it may not have the same properties as properly mixed.

Use smaller batches, and or find a different epoxy to match your working time

T
 

surferguy001

Seaman
Joined
Feb 12, 2010
Messages
70
Re: Using epoxy without hardener?

ahh... i mixed it an aluminum can! i couldn't figure out what i did different because it worked fine for me last week (i mixed in a small paper cup.) And i didn't mention yesterday that when i picked up the can it was probly around 150 degrees. thank you all for your help, im gonna stick to the 'recipe' and just mix in like a plastic container.
 

pigeon laker

Seaman Apprentice
Joined
Jun 19, 2008
Messages
47
Re: Using epoxy without hardener?

DO NOT use an aluminum container,I work with solvents and resins and have seen more than one reaction/explosion when these materials come in contact with each other.My company removed anything aluminum in our plant at a great expense to avoid a catastrophy.
 

erikgreen

Captain
Joined
Jan 8, 2007
Messages
3,105
Re: Using epoxy without hardener?

Epoxy won't care about the material the pot is made of.. I mix in lots of different containers. It will care about heat dissipation some.

What's more important is the surface to volume ratio of the epoxy in the container... in the same way that a large, flat piece of metal cools faster than a squat cube, the surface area of epoxy in (eg.) a quart can will let heat build up as compared to the same amount of epoxy in a paint tray.

Heat also accelerates the reaction that's generating it, IE in a can heat builds and speeds the reaction which makes more heat which speeds it up more.. you get a pot life of maybe 10 minutes in a can and 30 in a paint tray for the same epoxy.

Try it.

Erik
 
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