Polyester resin vs. epoxy resin: Which resin type do you need?

If you're diving into a creative project, whether it's woodworking or jewelry making, you’ve likely faced the polyester resin vs. epoxy resin conundrum. Both have their merits, but which one do you really need? r

The choice isn't as straightforward as it seems. That’s why we’ve put together this comparison guide to help you figure out which type suits your needs best. Let’s break down the strengths and weaknesses of these two popular resins and find out which one can handle all your plans.

What is polyester resin?

Polyester resin is a synthetic material created by a chemical reaction between organic acids and alcohols. It's a durable, flexible substance that's easy to mold and laminate. Polyester resin is used in everything from boat hulls and car parts to artistic sculptures and home renovations.

Polyester resin is also known for its relatively low cost and quick curing time, which means you won't have to wait around forever for your project to set. Plus, it's great for those on a budget.

What is epoxy resin?

Epoxy resin is a powerful adhesive that's good at sticking materials together. It's better at this than polyester resin because it can withstand water, chemicals, and environmental damage.

Epoxy resin has many uses, like fixing a crack in your basement floor or making a custom countertop. It’ll keep things stuck together for a long time. It’s also popular in construction for its strengthening and fixing structures. Artists and DIY fans also love it for making jewelry, coating surfaces, and crafting river tables. Additionally, it's used in electronics for insulation and protection.

Epoxy resin can be more expensive than polyester resin. However, its durability, versatility, and quality finish often make it worth the extra expense.

Epoxy vs. polyester resin: What are their key differences?

Polyester and epoxy resin have unique properties, strengths, and weaknesses that make them suitable for different projects. So, it's sometimes impossible to set them apart.

This guide will help by covering factors like durability, chemical and heat resistance, and ease of use. By the end, you'll confidently know what is resin and exactly which one to pick for your next project. 

In terms of strength and durability

When comparing polyester resin and epoxy resin  in terms of strength and durability, it’s clear that each has its unique advantages. Polyester resin is hard but can become brittle over time if not reinforced properly. On the other hand, epoxy resin exhibits incredible strength and flexibility, which makes it ideal for enduring heavy loads and stress.

Epoxy resin forms a stronger, more durable bond than polyester, which can crack or break under extreme conditions. With epoxy, you get superior resistance to environmental factors, which means it won’t degrade as quickly when exposed to water or chemicals. This feature is especially crucial in marine applications where materials like fiberglass and resin need to perform under tough conditions.

Plus, epoxy resin has a higher adhesive strength than polyester resin, so it has a more long-lasting bond. While polyester is easier to sand and work with, it simply doesn’t match the robust finish that epoxy provides. There are even fiberglass epoxy resin variants you can use for tasks like building a boat hull. 

In terms of chemical resistance

Resin is usually required to hold up against chemicals and other corrosive materials. In that aspect, when you compare the properties of polyester resin to epoxy resin, you’ll notice some distinct differences.

Polyester resin can’t stand up to chemical exposure like epoxy can. If you plan on exposing your project to solvents or acids, epoxy is your go-to choice. It won't break down when it’s in contact with harsh chemicals.

Polyester resin, on the other hand, is more likely to degrade over time when exposed to such substances. It works better for general-purpose projects where chemical exposure isn’t a concern. 

In terms of heat resistance

Chemicals are not the only substances that can affect resin. Heat exposure is another factor to consider when choosing between polyester and epoxy resin. And in this regard, epoxy outshines polyester.

Epoxy maintains its structural integrity at higher temperatures. It’s the go-to choice if your project will face extreme heat. Conversely, polyester resin tends to soften and distort under high temperatures. You might find your project warping if it's constantly exposed to heat. So, for heat-sensitive environments, polyester falls short.

Epoxy resin also provides better insulation properties. It doesn't just withstand heat, it minimizes heat transfer. This feature makes epoxy appealing for applications that need controlled thermal environments. 

In terms of the curing process

Resin is a liquid that hardens into a solid form through curing. The curing process involves the chemical reaction between the resin and a hardening agent or catalyst. And this is where epoxy and polyester differ greatly.

Epoxy resin cures consistently and predictably because of its chemical makeup. It naturally cures at room temperature, but you can speed up the process by adding heat. This makes it great for projects under tight deadlines.

However, curing polyester resin can be trickier. It depends greatly on getting the right mix of catalysts and the right temperature and humidity. If these aren't right, you might end up with a tacky finish or a project that doesn't cure properly.

With that said, how long does resin take to set? Epoxy resin needs at least 72 hours or 3 days to cure, but it’ll continue to dry for up to 2 weeks. Only then will it reach its maximum durability. Meanwhile, polyester resin takes only 12 hours to cure. 

Since epoxy resin takes longer to cure than polyester, you have more time to work on detailed projects. Polyester resin, on the other hand, is suitable for fast projects, but it leaves little room for mistakes or last-minute changes.

In terms of application and handling

When mixing, epoxy resin tends to be more forgiving because you don't need to be as precise with the proportions. Polyester, however, calls for a specific mix, or you'll face problems like uneven curing.

However, you need to handle epoxy carefully. It's known to contain chemicals that can irritate the skin, so make sure to wear gloves and a mask to protect yourself adequately. Similar precautions should be taken for polyester resin, as its styrene and organic peroxide content can cause burns and allergic reactions.

In terms of project suitability 

Epoxy resin is ideal for high-traffic areas because it's tough and long-lasting. Hence, it's often used for floor coating in commercial and residential settings. Polyester, on the other hand, is better suited for smaller projects like jewelry making or small art pieces.

For furniture assembly, epoxy resin also provides stronger adhesion, making it a go-to for joints that need to withstand weight and pressure. Polyester resin can work, too, but it's more brittle and doesn't offer the same level of durability.

Another popular application of resin is terrazzo flooring. Epoxy resin is used more often because of its highly customizable finish. Polyester resin may be cheaper but won't give you the same level of finish or wear resistance. 

However, it's crucial to take note that terrazzo flooring assembly should always be done by a professional, as there are safety concerns and specific techniques that need to be followed for both types of resin. 

Epoxy resin is also suitable for marine and outdoor projects due to its waterproof finish. Polyester can be used in similar applications, but it's not as durable as epoxy under water conditions.

Level up your home improvement projects with Airtasker

No matter the scope of your project, choosing the right resin can make all the difference. And remember, you don't have to tackle these projects alone.

Need help with epoxy floor coating for your home or new furniture setups for your living area?

Post your task on Airtasker and connect with experienced professionals who can get the job done efficiently. Here, you'll find skilled handypersons who are ready to transform your project ideas into reality.