Temperature resistance of epoxy

Can epoxy withstand heat? The answer to this depends on a number of factors. Each epoxy system has a different temperature resistance. A common question we get is "What is the temperature resistance of epoxy and how can I increase it?" We are happy to tell you more about this. After all, it is important to know how many degrees your epoxy can withstand and what you can do to improve temperature resistance after curing. In this article we'll give you more information about the temperature resistance of your epoxy product. In another article, we'll tell you more about working with epxoxy under high temperatures.

1. Composition of epoxy (what happens during curing)

Epoxy is a two-component resin system, epoxy is also called a plastic. These are so-called "thermosetting plastics." That means, once hardened, the plastic cannot be melted. In addition to thermosetting plastics, there are also "thermoplastic plastics." These can be re-melted after use, to produce other products. Epoxy must be weighed and mixed accurately. If the mixing ratio is incorrect, you will be left with resin or hardener during the reaction. This results in the epoxy not (or not completely) curing.

2. Temperature resistance for each epoxy system

Each thermoset has a certain heat resistance. This is called "glass transition temperature" (Tg). Below glass transition temperature the material reacts glassy. Above glass transition temperature the material reacts rubbery and you can even bend it slightly. In the table below we indicate the temperature resistance of the epoxy systems we sell.

Glass transition temperature (Tg) = the temperature at which epoxy becomes rubbery and flexible.
Epoxy system Temperature resistance* Temperature resistance (after postcure)
RESION Epoxy casting resin 40 - 45°C 45°C
RESION UV Epoxy 40 - 45°C 45°C
RESION LV, MVHV 40 - 45°C 45°C
RESION Universal epoxy resin (fast) 40 - 50°C 50°C
RESION Universal epoxy resin (slow)  40 - 50°C 50°C
RESION Epoxy coating transparent 40 - 45°C 50°C
RESION Epoxy for large castings 40 - 50°C 95°C
RESION Winter epoxy 40 - 50°C 50°C
RESION Epoxy Super Clear 40 - 45°C 70°C
Epoxy resin for high temperatures up to 130°C 40 - 50°C 145°C
Hexion RIM135 40 - 45°C 80°C
UltraCast 70 - 75°C 80°C
TotalCast 40 - 50°C 50°C
MasterCast 40 - 50°C 55°C

* after curing for 7 days at 21°C

3. Increasing the temperature resistance of epoxy

As shown in the table, it is possible to subsequently increase the temperature resistance of the product you have made, such as a table or a set of coasters, so that your epoxy product can withstand heat better. This can be done in different ways and we will explain these ways one by one.

  • Option 1: apply a layer of heat-resistant epoxy
    A coat of heat-resistant epoxy helps to keep the surface looking nice. If you want a transparent, glossy layer, then Eli-Chem UltraCast Epoxy resin is first choice. This epoxy has a temperature resistance of approximately 70ºC and is therefore resistant to, for example, a hot cup of coffee or tea. This epoxy also has no color, hardens fairly quickly and gives a beautiful surface. The epoxy is UV resistant. This does not affect the appearance! You can also use Motip Clear Varnish to increase heat resistance. Read the instructions carefully.
  • Option 2: apply a coat of DD paint
    A coat of DD Paint can also help to increase the heat resistance of the surface. DD paint is a heat-resistant and UV-filtering 2 component PU paint. This can be brushed, rolled or sprayed and is available in transparent or colour. DD paint increases the scratch resistance and heat resistance of epoxy surfaces.

  • Option 3: post-cure
    The temperature resistance of most epoxy systems can be increased with a post-cure. This means you let the epoxy cure for several hours at a higher temperature. What temperature this should be and how long the curing time is can be read in the technical datasheet.

    Post-curing in the mould: after curing, place the mould in the oven at a temperature around the maximum Tg (glass transition temperature).
                                                                                                                                                                                                                                                                                                                           Post-curing outside the mould: increase the temperature slowly. For small castings 10-15 degrees per hour to 15 degrees below Tg. Keep it at this temperature for about 5 hours.
For questions about post-cure contact us!

4. What happens if the temperature exceeds the temperature resistance?

The temperature resistance as we have indicated in the table is the so-called "glass transition temperature." Below this temperature the material reacts glassy, above this temperature rubbery. If the temperature rises above glass transition temperature, then used glass fabric or effects (such as circles, streaks, bending) may become visible as relief on the surface.

Only at 200 to 250 degrees the epoxy will get too hot and lose its chemical structure. The epoxy is then charring (burning).

More information about temperature resistance?

Do you have questions about heat resistance, post-cure or related topics? Please feel free to contact our specialists! We are happy to help you with your project!

T: +31 (0)85 022 00 90
E: support@polyestershoppen.com
Or chat live with us via the website!

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Temperature resistance of epoxy

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