What is polyester resin and what can you use it for? In this article, we explain the basics of working with polyester resin. At Polyestershoppen, you will find all the materials you need to start your polyester project. Our specialists are also ready to advise you and help you get started with your project. So feel free to contact us!
Polyester is a synthetic resin that hardens after adding a hardener. This process is irreversible, meaning polyester cannot be remelted once cured. Polyester does not rot or rust and can be processed with a minimum set of tools. With a polyester repair kit, you can easily carry out minor repairs to items like caravans, boats, or swimming pools.
Polyester is usually combined with fiberglass to produce a strong, impact-resistant, and rigid product. Examples of polyester products include boats, ponds, swimming pools, car bumpers, gutters, artwork, scooter fairings, waterproof linings, and much more.
Combining polyester resin with fiberglass is called laminating. The resulting plastic material is referred to as a laminate, named after the various layers of fiberglass it consists of.
Polyester is ideal for products where design freedom comes first. Polyester with fiberglass is always laminated against a mold (which can be temporary or permanent). This temporary mold can be made from various materials and can also become an integral part of the structure. Examples of molds include: polyester molds as well as molds made of wood, foam, plaster, or chicken wire. You can manufacture products inside a mold or apply a protective lining over objects. In short, as long as you have a substrate to laminate the polyester against, it can be made using polyester.
Polyester products can be finished in several ways. Against a smooth mold, gelcoat can be applied: a fully colored layer of approximately 0.3 mm thickness based on polyester. This layer adopts the exact surface texture of the mold, usually aiming for a mirror-smooth finish. For filling small pinholes and achieving a smooth finish, use polyester putty. This product cures quickly and is easy to sand.
| Application | Properties | |
| RESION Polyester laminating resin |
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| RESION Polyester casting resin |
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| RESION Vinylester resin |
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| RESION Polyester topcoat |
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| RESION Polyester gelcoat |
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| RESION tooling gelcoat |
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| RESION tooling resin |
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| RESION sanding gelcoat |
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| Polyester putty |
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| Polyester glass fiber putty |
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A polyester topcoat can be applied on the reverse side of a polyester product or when coating an object. This coat is also an approximately 0.3 mm thick layer colored through and through, but its surface texture depends mainly on the application method (brush, roller, or spray) and will always feature a semi-gloss finish with some light texture. It is possible to sand this topcoat smooth and/or polish it to a high gloss.
Polyester has many applications. For several common projects, we have prepared detailed guides:
When working with polyester resin, we usually use chopped strand mat (CSM). This mat is made of randomly oriented glass fibers roughly 5 cm long. These fibers are bound together by a binder that dissolves in polyester resin. Applying polyester resin to the mat softens it, allowing it to conform easily to the shape underneath. Once cured, the final product derives its structural strength from the glass fibers and maintains its shape via the resin matrix.
| Application | Properties | |
| Fiberglass mat 225g/m2 |
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| Fiberglass mat 300g/m2 |
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| Fiberglass mat 450g/m2 |
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| Surface tissue 30g/m2 |
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| Woven roving 300g/m2 |
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| Woven roving 600g/m2 |
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| Spherecore 3 mm |
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| Spherecore 4 mm |
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Never mix more polyester resin than you can apply within 10 minutes. Approximately 2% hardener is added to polyester resin.
The chart below indicates how much hardener you need for polyester laminating resin.
| Hardener | |||
| 12-17 ℃ | 18-23 ℃ | 23-30 ℃ | |
| Resin: | 2.5% | 2% | 1.5% |
| 100 grams | 2.5 ml | 2 ml | 1.5 ml |
| 250 grams | 6.25 ml | 5 ml | 3.75 ml |
| 500 grams | 12.5 ml | 10 ml | 7.5 ml |
| 1000 grams | 25 ml | 20 ml | 15 ml |
The chart below indicates how much hardener you need for polyester casting resin.
| MEKP | Working time | Curing time | |
| Thickness 1 cm | 1% | 25 min. | 10 hours |
| 1.5% | 22 min. | 3 hours | |
| 2% | 20 min. | 2.5 hours | |
| Thickness 3 cm | 0.4% | 40 min. | 2 hours |
| 0.7% | 27 min. | 1.5 hours | |
| 1% | 25 min. | 45 min. | |
| Thickness 6 cm | 0.3% | 48 min. | 45 min. |
| 0.35% | 43 min. | 30 min. | |
| 0.4% | 40 min. | 30 min. |
Laminating is the process of building thickness and strength using reinforcement materials such as fiberglass mat and polyester laminating resin. The reinforcement material is thoroughly "wetted out" with the polyester resin using a brush or roller.
Commonly used tools during laminating:
After laminating, the laminate surface may feel somewhat rough. To finish the laminate and enhance its weather resistance, you can apply a polyester topcoat. Lightly sand the laminate using 60-grit sandpaper to prepare it for topcoat application.
In the video above, Herman demonstrates how to finish polyester with a polyester topcoat. Once cured, your product is protected against weather conditions and displays your desired color.
Purchase your polyester repair kit at Polyestershoppen.nl. Our kit is fully equipped with all the necessary tools to perform a variety of repairs—everything is included! Easily repair holes, cracks, and fractures in polyester items. In addition to small repair kits, we also supply polyester repair packages for larger projects, such as our laminating kit.
Styrene vapors emitted by polyester are harmful to health and the environment. Ensure adequate ventilation in your workspace and preferably wear a half-mask respirator, especially in confined spaces. Make sure to avoid skin contact with polyester resin and hardener by wearing appropriate gloves, such as nitrile gloves or work gloves.
Other commonly used safety equipment:
As you have read in the article above, working with polyester is straightforward. On this page, we have explained to the best of our knowledge how polyester is processed, the options available, and what to keep in mind during application. There are countless possibilities when working with polyester. Whether you are building swimming pools, shower enclosures, automotive parts, furniture, or artwork, polyester can be applied in almost any situation. The possibilities are virtually endless. Do you still have questions after reading this article, or do you need advice for your specific project? Feel free to contact our specialists. They are happy to assist you!
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