What is the difference between epoxy and polyester?

The differences between epoxy and polyester are important to know if you are considering working with these materials. In this article, we will discuss the main properties and applications of both materials. This way you know exactly which material is most suitable for your project and you can get started with peace of mind.

Do you have any questions about epoxy or polyester? If so, feel free to contact our expert support team!

What are epoxy and polyester?

Epoxy and polyester are both synthetic resins, meaning they are composed of synthetic materials. Both epoxy and polyester consist of two components: a base (component A) and a hardener (component B). If you mix both components together, a chemical reaction occurs that releases heat. This forms a hard, strong and durable connection. Synthetic resins such as epoxy and polyester are popular in (boat) construction, industry and do-it-yourself enthusiasts because of their versatility, strength and durability. Although they may seem very similar at first glance, there are a number of important differences between epoxy and polyester.

Properties of epoxy

Epoxy is a very strong and durable material that is known for its excellent adhesion to almost all surfaces. It is resistant to chemicals and water and boasts high mechanical resistance. Thanks to the UV stabiliser, epoxy is also suitable for outdoor applications. In addition, epoxy is very dimensionally stable, which means that it does not shrink during curing. This makes it ideal for repairing cracks and holes, coating floors and bonding various materials. Epoxy is also popular with hobbyists for making jewelry, coasters, artwork and repairing objects.

Properties of polyester

Polyester is a cheaper alternative to epoxy and is often used for larger projects where costs play an important role. It is often used to make glass fiber reinforced plastic (GRP) objects, such as boats, car parts and swimming pools. Polyester resin is also suitable for making molds and casting objects. 

When do you choose epoxy and when do you choose polyester?

Now that you know what epoxy and polyester are, it's time to discuss the main differences between these two materials. We look at the adhesion, UV resistance, waterproofing, chemical resistance, shrinkage, processing (odor) and price of both materials.

  • Adhesion: if you are looking for a material with excellent adhesion to almost all surfaces, epoxy is the best choice. Epoxy adheres effortlessly to steel, aluminum, concrete, wood, stone, polyester and more materials. Polyester generally adheres less well and can peel off if not prepared properly. You generally need less preparation for epoxy.

  • UV resistance: are you going to make something that will be left outside and exposed to sunlight? Then polyester is the best choice. Polyester resin has better UV resistance than epoxy resin. This means that polyester discolors or yellows less quickly under the influence of sunlight. To prevent yellowing of epoxy, you can choose to use a UV-stabiliser. This significantly increases the UV stability of epoxy. At Polyestershoppen you will also find high-tech epoxy systems with a built-in UV filter, such as RESION UV Epoxy and RESION Epoxy for large castings.

  • Watertightness: epoxy is water and vapor proof. Polyester, on the other hand, is only waterproof only waterproof if it is finished with a gelcoat or an epoxy system.

  • Chemical resistance: epoxy resin is more resistant to chemicals, such as acids, bases and solvents. This makes epoxy extremely suitable for applications where the material comes into contact with aggressive substances (such as in the chemical industry) or when protecting concrete floors against chemicals. The mechanical resistance of epoxy is also 3 to 4 times stronger than polyester.

  • Shrinkage: if you want a sleek finish without shrinkage cracks, epoxy is the way to go. Polyester can shrink up to about 5% during curing. This can lead to a less attractive result.

  • Processing (odour): unlike polyester, epoxy resin hardly emits any odor during processing. You do not need a vapor mask to process epoxy and you can work indoors (if you can ventilate the room well). Are you going to work with polyester? Then work outside or in a very well ventilated area. In addition, always use a suitable fume mask. In short: polyester stinks, epoxy does not.

  • Price: an important difference between epoxy and polyester is the price. Polyester is generally cheaper than epoxy. Do you have a limited budget or are you going to carry out a large project? Then polyester can be a cheaper option.

As you can see, both materials have advantages and disadvantages. The choice between epoxy and polyester therefore often depends on your specific project and needs. It is important to carefully consider which properties are most important for your application. We are happy to help you with this choice. So please feel free to contact our specialists.

Conclusion: epoxy or polyester?

The differences between epoxy and polyester are mainly in the properties of the materials (such as adhesion, chemical resistance, UV resistance and shrinkage) and in the costs. Epoxy is a stronger and more durable material that is better suited for applications where good adhesion, waterproofing and chemical resistance are important. Polyester is a cheaper and more flexible material that is suitable for larger projects and applications where costs play an important role. By comparing the properties and applications of both materials, you can make the right choice for your project.

We have listed the properties of epoxy and polyester for you:

Epoxy properties Polyester properties
Adhesion to many materials Frequent pre-treatment required
UV-resistant by adding stabilisers High UV resistance
Waterproof Not waterproof
High chemical resistance Less resistant to chemicals
Odourless (solvent-free)  Strong odour
Hardly shrinks  Can shrink up to approx. 5%
More expensive Cheaper

Need more information on epoxy or polyester?

Do you still have questions about epoxy or polyester after reading this article? Then feel free to contact our expert support team. We are more than happy to offer free, non-obligation advice! 

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