We all know epoxy as a durable, hard-curing, and even food-safe when cured. It’s very commonly used as an adhesive, coating, or even casting material. However, while epoxy is very versatile, it’s not very dependable when it comes to high heat applications.
So, is epoxy heat resistant? Unfortunately, epoxy resin is not heat resistant. Epoxy resin can only withstand heat up to 302°F. Fortunately, there are many types of hard-curing resins, and each has a different degree of heat resistance.
If you want to learn more about different types of resins, especially the types that are suitable for a high heat application, this article will tell you all about them.
Types Of Resin And Their Heat Resistance
There are various types of hard-curing resins available, but how they work is quite similar.
Most of them make up of two parts: a resin base and a hardener. When a hardener is mixed in with the resin, a chemical reaction happens, and the resin will start to cure immediately.
Depending on the type of resin, this reaction can happen over a couple of minutes or over several days.
One exception to this is UV resin, which is cured when it is exposed to UV light (similar to gel nail polish). As a result, UV resin only comes in one part, and the chemical reaction happens when it is exposed to UV light.
As we’ve mentioned, there are a few types of resin that are commonly used for DIYers, including UV resin, polyurethane resin, epoxy resin, and high-temperature epoxy. Below is a summary of their heat resistance.
| Type of Resin | Heat Resistance |
| UV Resin | Up to 120°F |
| Epoxy Resin | Up to 190°F |
| Polyurethane Resin | Up to 300°F |
| High-Temperature Epoxy | Up to 600°F |
What do we mean by heat resistance? The temperatures above are the temperature at which the resin will start to ‘melt.’
This is because the curing process of resin is reversible, and when exposed to these temperatures, the curing process will be reversed, and the resin will start to soften to its uncured state. That’s why the resin appears to ‘melt’ when it is met with high heat.
Heat resistance comes in handy in a lot of scenarios. Resin is food-safe when it is cured, but if the resin starts to melt at high heat, you won’t be able to use your resin cups and bowls to handle hot food or drinks. Using heat-resistant epoxy will solve that problem.
Similarly, your dishwasher runs at a temperature of about 120 – 170°F in order to sterilize your dishes. If your resin can’t handle that temperature, it will melt in the dishwasher and ruin the entire thing!
As you can tell from the list above, UV resin is the least heat-resistant, only able to withstand the heat of about 120°F. If you want something very heat resistant, you can opt for high-temperature epoxy, which is formulated to withstand the heat of up to 600°F.
Let’s take a look at each type below.
UV Resin
Unlike other types of resins, UV resin doesn’t require a hardener to cure. It only needs exposure to ultraviolet light to activate its chemical reaction, which allows it to set and cure very quickly.
UV resin is used in various casting, coating, or adhesive applications. The length of time that you need to expose the resin to UV light depends on the size and thickness of the application – the thicker and larger the resin, the longer it will take to cure.
The major advantage of using UV resin is that it gives you more time to work. If you use traditional epoxy, it must be mixed quickly and will start to harden immediately after mixing. With UV resin, you have more control because the resin doesn’t cure until it is activated by UV light.
UV resin is also fast drying, so you don’t have to wait days or weeks to finish an entire project. In addition, UV doesn’t require mixing as traditional epoxy does, so you can avoid the risks of errors when working with this type of resin.
However, the major disadvantage of UV resin, besides its short shelf life (only 6 months), is that the cured product is not very heat resistant.
It will start to melt at 150°F, which means it doesn’t take much to ruin the resin – even leaving the resin creation in a car during a hot day can completely ruin it!
Epoxy Resin
Epoxy resin is a two-part solution that is made by mixing equal parts of epoxy and hardener. Once mixed, you can start to use it to cast into a mold or apply it as a sealant, and it will cure into a solid, clear, and brilliant surface.
One of the main advantages of epoxy resin is that it is extremely durable.
The material has been used in many different industries for decades, and it has proven itself to be an effective solution for many different applications. It can be used on both interior and exterior surfaces, and it does not chip or crack easily because of its hardness.
Epoxy resins are also resistant to water and solvents, making them ideal for sealing wood furniture and especially useful when sealing flooring. They are also used as adhesives for ceramics and for the repair of broken ceramics.
One disadvantage of epoxy is that it can take a few days or even a full week to cure completely, so if you want to pour multiple layers, it can take quite a while to complete a project.
After it’s cured, the epoxy can also yellow over time, especially if it is exposed to sunlight. If this is a concern, you can opt for UV-resistant epoxy formulas.
And of course, epoxy resin is not very heat resistant, even after it’s cured to become food safe. One trip through the dishwasher (see our article Is Resin Dishwasher Safe?) is all it takes for the epoxy to lose its integrity, so it’s not a great option for things that need to handle high heat.
Polyurethane Resin
Polyurethane resin is a highly durable resin that’s suitable for use in a variety of industries, from automotive repair and construction to electronics. For DIYers, it’s commonly used as a sealant and adhesive.
Polyurethane resin also shares some of the same characteristics as epoxy resin in that it will start to set immediately after curing, and after mixing, it’s in a liquid form that can be used to cast in moulds or as a sealant or adhesive.
Compared to epoxy resin, it’s considered more heat resistant and doesn’t shrink after curing. This makes polyurethane resin more versatile in more demanding applications, for example, in construction.
However, for DIY projects, polyurethane resin also has some disadvantages, namely that it’s not as waterproof as epoxy resin. It can absorb moisture when curing, and this process is known as foaming. Compared to epoxy, it’s also not as strong an adhesive.
Similar to epoxy resin, polyurethane resin can also be damaged by sunlight and will start to yellow over time. It will require a UV-protective additive to prevent this issue.
High-Temperature Epoxy
As you can tell, epoxy is beloved by many people because of how durable, versatile, and attractive it is. However, one disadvantage of epoxy resin is that it’s not heat-resistant.
That’s why some manufacturers have come up with a formula for high-temperature epoxy, which can withstand the extreme heat of up to 600°F (this number depends on the manufacturer).
High heat epoxy products are also commonly reinforced with various types of materials, such as titanium. These additions allow them to endure high temperatures while still maintaining the attractive characteristics of epoxy resin.
High heat epoxy resin can be used in harsh environments due to its ability to resist exposure to higher temperatures. High heat epoxy is commonly used in electrical and mechanical repairs since these are the applications that are most demanding.
Tips And Tricks For Heat Resistant Epoxy Resin
The step that can most often go wrong when working with epoxy is the mixing part. You should follow the instructions provided by the manufacturer to the letter so that the epoxy will turn out perfect.
The humidity and temperature of your working environment can also affect how well the epoxy will cure. Too much moisture and the epoxy may look cloudy after it’s cured. If the room temperature is too low, the epoxy may also take longer to cure.
If you are pouring your epoxy, you can use a blow torch to remove any bubbles trapped inside the epoxy. However, you should keep the heat at least 7 – 8 inches away from the surface to avoid dimpling.
Keep in mind that if you add chemical-based pigments or powder to the epoxy, you can also change the chemical makeup of the solution, which can affect how heat-resistant the epoxy will turn out.
If that’s the case, you should add a clear layer of epoxy on top of the mixed epoxy so that the top layer will still maintain its heat resistance.
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