Epoxy vs. Polyester Resin:  Everything You Need to Know


When you’re working on a resin-based project, you’ll encounter several crucial decisions that you’ll need to make. Perhaps the most significant of these choices is what kind of resin you’re going to use. There are various types of resin available today, each with its own composite mixture. The type of material that you should use will depend on the nature of your project.

Today, we’re going to look at the difference between epoxy and resin made with polyester so that you can make an informed choice.

Epoxy Characteristics

You can find many types of resin on the market, all of which are designed to be flexible and versatile. The most popular choice for projects is either epoxy or polyester resin. Let’s start by examining the characteristics of epoxy resin.

  • High-strength design with excellent flexibility
  • Fantastic shelf life of up to a few years with proper storage
  • No option to vary the cure time of epoxy resin
  • Slightly more expensive than polyester resin
  • Does not shrink when cured like different types of resin
  • Perfect for applying as a thin film
  • Very little odor – doesn’t usually require the use of a mask
  • Resistant to cracking, wear, peeling, and corrosion
  • Moisture-resistance
  • Great bonding strength up to 2,000 PSI

Polyester Resin Characteristics

To decide between polyester resin vs epoxy, you need to know how each product works. So, what is poly resin? Polyester is one of the more common kinds of resin available today due to its affordability. Characteristics include:

  • Brittle design prone to small cracks
  • Shelf life ranging from six months to a year
  • Options to adjust the cure time by adding MEKP catalyst
  • Less expensive than epoxy resin
  • Significant off-gasses and flammable fumes
  • Does not cure well as a thin film
  • Water permeable when cured
  • Bonding strength of less than 500 PSI
  • Does not bond to epoxy resin

The Different Types of Resin

Knowing the difference between polyester resin vs epoxy ensures that you’ll use the right product for your project. However, in some circumstances, neither of these two options is suitable. In this case, you may need to consider one of the other resins on the market.

If you need to go beyond the debate of epoxy vs polyester resin for your project, here are some of the types of resin you should consider: 

  • Phenolic resins: A thermosetting resin that is heat-resistant, strong, and corrosion-resistant.
  • Alkyd resins: Made with thermoplastic polyester, these resins are excellent for electricals.
  • Polycarbonate resins: These are thermoplastics with a high refractive index, ideal for metal replacement.
  • Polyamide resins: Strong and resistant, these are great for gears, tires, and sutures.
  • Polyurethane resins: These are very versatile and can adhere well to substrates.
  • Silicone resins: Ideal for oxidative and thermal stability.
  • Acrylic resins: Created with acrylic acid, these resins are ideal for structural panels.
  • Polypropylene resins: Frequently used with electronic components and toys.

Though epoxy and polyester resins are common choices for many repairs and jobs, you may find a better option depending on the unique needs of your project. 

Epoxy vs Polyester Resin

Deciding on whether to use epoxy resin vs polyester resin can seem tricky at first. However, when you carefully consider your project and your intended goals, you can start to move in the right direction. 

For example, polyester resin is ideal for projects that involve fiberglass layup techniques, like when you’re building a boat. Polyester resin doesn’t cure when it’s aired out. Therefore, it’s perfect for jobs when every resin application needs to bind to the previously applied layer. 

However, if you’re looking at polyester vs. epoxy resin for a repair, polyester resin might be versatile and durable, but it’s not going to withstand a lot of pressure. Epoxy resin is stronger and can adhere well to cured polyester, while polyester cannot adhere to epoxy.

If you can use either type of resin for your project, you may want to consider the costs of each. Epoxy resin is a lot more expensive than polyester, making it less accessible for a larger job or repair. If you’re in a hurry, epoxy resin cures very fast if you’re using the right techniques.

Choosing the Right Resin

Now that you know the difference between polyester and epoxy resin, you can make an informed choice for your next project. At Plastic Materials, we have been manufacturing products to aid resin crafters for years. If you have any questions about epoxy vs polyester resin, get in touch!, We’d love to answer your questions about epoxy resin, polyester resin, and more.

With over 50 years of experience in the composite and fiberglass industry, you can trust us to provide you with high-quality resin at competitive prices. We’re committed to helping businesses large and small create the best products on the market. 

If you need products that clean, protect, polish, and shine a wide variety of surfaces, choose Plastic Materials. 

Subscribe to our Newsletter

Leave a Reply

Your email address will not be published. Required fields are marked *

Serving The Composites Industry Since 1966