One of the best ways to join two bits of wood or other material together is to use an epoxy. This is a two-part glue that, when you mix the two parts, forms a strong, waterproof and lasting bond that is strong enough that it can even replace missing parts of the wood. But is epoxy flammable and should we be careful of flames and sparks when using it or where it has been used?
The curing agent of the two part epoxy is not flammable. The other half of the epoxy is flammable. When the two have been mixed, the mixture is combustible while it is curing but it would require a very high heat to set it on fire – the wood would burn first. The end product, cured epoxy, is not flammable and shouldn’t catch fire.
So Epoxy is both flammable and not flammable. Let’s take a closer look at epoxy and it’s fire hazards.
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Also read: What Makes Something Flammable?
Does Epoxy Catch Fire?
Epoxy and/or it’s parts can catch fire in the right circumstances.
Technically speaking, epoxy isn’t epoxy until the two halves have been mixed. When they are mixed, they are known as “curing epoxy”. While the epoxy is curing, it starts to generate heat as the reaction between the two components of the epoxy is exothermic (that is, it gives out heat).
Now, in most cases, this results in some fumes being given off and it looks like the epoxy is “smoking”, but it’s not on fire, it’s just that the evaporating gasses are slightly visible.
But, if you were to pour enough cured epoxy on wood, you might have a bit of a problem on your hands. The temperatures generated by this reaction can exceed 400 degrees Fahrenheit and while this is not hot enough for the epoxy to catch fire, it might be enough for the wood that you are gluing to catch fire.
As a rule of thumb, it’s a good idea to keep an eye on the curing temperature of your epoxy and try to keep it below 100 degrees Fahrenheit.
However, if you want a more exact number, check the bottle that the epoxy comes in. As there are many different formulations of epoxy, there is some variation on the precise safe curing temperature of each.
It’s worth nothing that this isn’t just a fire risk. Even if you don’t get a fire from your curing epoxy – you may cause the final cured epoxy to have splits and bubbles in it if it gets too hot during the curing process.
We would note that some people try to remove these bubbles with a propane torch (or just a heat gun) – while this will, probably, get rid of the bubbles, it does, dramatically, increase the risks of you burning the curing epoxy and increasing the amount of fumes being released.
Also read: Is Glass Flammable?
How Flammable Is Epoxy Resin?
Once the curing process is completed, the end product is known as epoxy resin. And epoxy resin is not at all flammable. That doesn’t mean, again, that it won’t burn.
Everything will burn if you make it hot enough but under almost all ordinary circumstances, you won’t be able to set cured epoxy resin on fire.
Take a look here:
Also read: Is Resin Flammable? [Epoxy, Polyester]
At What Temperature Does It Ignite And Burn?
The strength of epoxy resins begins to diminish at temperatures over 350 degrees Fahrenheit as it will being to melt. But it can take up to 1500 degrees Celsius, that is 2,750 degrees Fahrenheit, to set an epoxy resin on fire.
Also read: Is Tear Gas Flammable? Can It Ignite?
What About Dry Epoxy?
Dry epoxy is epoxy resin and it is not flammable. Interestingly, it is also water-resistant.
Is It Fire Resistant?
Yes, epoxy (cured epoxy resin, at least) is fire resistant. However, it’s worth noting that when epoxy is used a wood glue – that fire resistance isn’t that important. While the epoxy may not burn easily, the wood around it certainly will.
You could coat wood in epoxy to make it less combustible, but this would be very expensive and not terribly practical on most projects. There are easier and cheaper ways to ensure that the wood is less likely to burn without using epoxy.
This video goes into more detail:
One part of two-part epoxy is, usually, flammable. The curing agent is not, normally, flammable.
Though that doesn’t mean it’s completely safe to work with. Many curing agents are corrosive and should not be in contact with your skin and they can also be toxic. This is also true of any fumes that are released from these agents.
The main epoxy element is flammable. This is also true of the fumes that it gives off. You should always work with epoxy outdoors or in a very well-ventilated space because of this and the potential toxicity of the curing agent.
What Happens If It Gets Too Hot?
If epoxy gets too hot, then you risk it damaging the wood that it is meant to hold together.
You can also risk the finished strength of the epoxy resin (it will get weaker the hotter it becomes), it may crack the finish on the epoxy, and you may also find that you get bubbles on the surface of the epoxy resin.
Are The Fumes Flammable?
The fumes of the one part of the epoxy mix, that is flammable, are flammable. Once the epoxy begins to cure, however, the fumes should not be flammable.
They are toxic though and that means you should work in a very well-ventilated place when working with epoxy – ideally, work with it outside. And if you are breathing in any fumes, you should wear a respirator.