Polyester Resin Guide: How to Use It, Types, and What You Need
Short Answer
Polyester resin is the most widely used material for fiberglass repair, boat building, and composite construction. It is affordable, fast-curing, and ideal for laminating fiberglass cloth, mat, and structural parts.
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What is Polyester Resin?
Polyester resin is a thermosetting resin used in fiberglass applications to create strong, durable composite structures. It is activated using MEKP catalyst and cures through an exothermic reaction.
Polyester resin is the most common type of fiberglass resin used in boat repair, surfboard building, and composite manufacturing.
It is commonly used in:
- Boat repair and marine construction
- Fiberglass layups and laminating
- Surfboard building
- Mold making and composite parts
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Types of Polyester Resin (What You Actually Sell)
General Purpose Polyester Resin (Aropol 67700)
General purpose polyester resin like Aropol 67700 is designed for marine and structural applications.
- Used for hand lay-up and spray-up processes
- Designed for demanding marine environments
- Improved fatigue resistance (important for boats)
- Consistent gel times and curing performance
This is your go-to resin for:
- Boat hull repair
- Transoms and stringers
- General fiberglass work
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Surfboard Polyester Resin (Silmar 249A / 249B)
Silmar 249A/B surfboard resin is specifically designed for surfboard construction and high-clarity laminations.
- Water-clear finish for color-critical applications
- Low viscosity for easy wet-out
- Room temperature cure system
- 249A includes UV stabilizer for durability
This is best for:
- Surfboard laminations
- Gloss coats
- Clear or pigmented finishes
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Polyester Resin vs Epoxy Resin
| Feature | Polyester Resin | Epoxy Resin |
|---|---|---|
| Cost | Lower | Higher |
| Strength | Good | Excellent |
| Ease of Use | Easy | Moderate |
| Best Use | Boat repair, surfboards | High-performance laminates |
Shop epoxy resin here if you need higher strength or bonding.
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How to Use Polyester Resin
- Measure resin into a mixing container
- Add MEKP catalyst (typically ~1–2%)
- Mix thoroughly
- Apply to fiberglass cloth or mat
- Allow to cure fully before sanding or coating
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What You Need for Polyester Resin
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Common Mistakes to Avoid
- Adding too much catalyst (causes overheating)
- Not mixing thoroughly
- Working in temperatures that are too cold or too hot
- Applying too thick at once
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Which Polyester Resin Should You Choose?
Choose Aropol 67700 if:
- You are doing boat repair or structural fiberglass
- You need durability and fatigue resistance
Choose Silmar 249A/B if:
- You are building surfboards
- You need a clear, high-quality finish
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Shop Polyester Resin
Shop General Purpose Polyester Resin
Shop Surfboard Polyester Resin
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Frequently Asked Questions
What is polyester resin used for?
Polyester resin is used for fiberglass repair, boat building, surfboards, and composite construction.
Is polyester resin waterproof?
Yes, when properly cured and sealed, polyester resin is water resistant and suitable for marine use.
What is the difference between polyester and epoxy resin?
Polyester resin is more affordable and easier to use, while epoxy offers higher strength and adhesion.
Need Help?
Call us or email orders@fiberglassflorida.com and we’ll help you choose the right resin for your project.
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