Polyurethane vs. Epoxy (What’s The Difference?)

You can use polyurethane or epoxy for your floor or concrete. But, what’s the difference between them?

The main difference is that epoxy is more durable and harder and you can use it on high-traffic surfaces, such as factories and warehouses. In comparison, you can use polyurethane for medium-traffic surfaces, such as house floors.

Polyurethane is softer and more flexible, but its drying time is affected by humid conditions, On the other hand, epoxy has better adhesive qualities, especially for concrete surfaces, and can cure (dry) even in humid conditions.

Epoxy Paint

What is Epoxy Paint?

Epoxy paint is a strong paint that comes in 2 parts; resin and hardener. You must mix both parts in a ratio of 1:1 before using. The mixture of both parts creates a strong layer (film) known as epoxy.

There are also 1 part epoxy paints that you don’t need to mix. But, 1 part isn’t as durable as 2 part epoxy. Also, there are different variations of the paint. For example, you can get flexible, floor, fast-settings epoxy, etc.

The paint has impressive bonding qualities, especially for concrete and masonry surfaces. The increased bonding qualities are due to the chemical reaction when two parts are mixed.

Also, it has a thick flow, meaning it will take longer to dry and cure. For instance, 2-part epoxy flooring can take up to 7 days to cure. However, the paint isn’t affected by humid conditions and will cure regardless of the humid levels.

This paint can’t cope well with temperature changes because the finish is rigid. So, it’s best to use it on floors and concretes that aren’t exposed to temperature changes. Also, it tends to yellow over time if exposed to UV rays. 

Polyurethane

What is Polyurethane?

Polyurethane is a plastic-like sealant used as a topcoat (or sealant) to protect the material (or finish) underneath.

When dry, it forms a glossy layer over the surface. This glossy layer is water-resistant, chip-resistant, and sometimes UV-resistant. This makes its finish durable.

Since polyurethane contains plasticizers in its formula, the finish is flexible. As a result, it can cope with temperature changes.

It has a quick-drying time (compared to other sealants). For example, water-based polyurethane fully dries within 24 hours, while oil-based polyurethane cures (fully dries) within 48 hours. You can also get different sheen finishes, such as medium-gloss or high-gloss.

Epoxy vs Polyurethane

So which of these finishes is better? Let’s go deeper into the characteristics of both finishes to bring out their differences, strengths, and weaknesses.

Paint Make-Up

Paint Make-Up

Both sealants have different make-up and formation.

Polyurethane is obtained from the reaction between polyols and diisocyanates or isocyanate compounds. On the other hand, epoxy is obtained from the reaction between a resin and hardener, which you must mix manually.

The difference in paint formula gives both finishes some different features. For instance, epoxy is known to be thicker because you have to mix two equal coatings (or parts) to make it.

Flexibility

Paint flexibility refers to the elasticity of the paint.

Polyurethane is more flexible than epoxy because it has plasticizers in the formula. Its plastic nature makes it stretch and contract based on temperature changes. This gives it improved flexibility.

On the other hand, epoxy paints are more rigid, hard, and brittle. So, it will crack if exposed to temperature changes.

Paint Drying

Polyurethane dries faster than epoxy. For example, water-based polyurethane dries enough for a re-coat within 8 hours, while oil-based polyurethane dries enough for a re-coat within 24 hours. On the other hand, epoxy must cure for 7 days before you can use or clean it. 

However, epoxy isn’t affected by humid conditions, while polyurethane is. So, if the humidity levels are too high, it will take longer to dry.

Paint Adhesion

Epoxy has better bonding qualities than polyurethane, especially for concrete surfaces. That’s because it is made from two compounds that improve paint adhesion; resin and hardener. When mixed, these two compounds produce a finish that will bind to any material. 

Polyurethane also has good adhesive qualities but doesn’t stick as well because it doesn’t penetrate the surface as much as other sealants.

However, for both sealants to stick, you must prep the surface before applying them. 

Durability

Both sealants are durable and strong enough. For instance, polyurethane is more flexible and can adapt to temperature changes. So, if used outdoors, it is more durable than epoxy.

However, for basement floors or indoor concrete, epoxy is more durable than polyurethane because it forms a thick layer that is strong, hard, and durable. Since indoor surfaces aren’t exposed to temperature changes, the epoxy finish will last years before it starts to chip off. 

Paint Hardness

Epoxy is harder than polyurethane. When dry, 2-part epoxy forms a hard sheen layer that is hard, durable, and strong. Its hardness makes it ideal for surfaces that will see heavy usage.

On the other hand, polyurethane has a thick plastic-like finish that is softer.

Paint Application

To apply polyurethane, you can use a spray gun, paint roller, paintbrush, or a rag (wiping it on the surface). However, epoxy paint can only be applied with a roller.

Paint Variety

Polyurethane offers more shades, types, and finishes. It comes in two types; oil and water-based. But, you can choose different sheen finishes; satin, medium-gloss, or high-gloss. 

On the other hand, epoxy has a limited range of choices. All you get is a strong and hard coating since the paint isn’t designed for decor or aesthetics.

Indoor or Outdoor Use

For outdoor, polyurethane is better than epoxy because it is flexible and can cope with temperature changes. 

For indoors, epoxy is better than polyurethane because it forms a hard, rigid coating that can withstand heavy weights and high foot traffic. That’s why it is used in warehouses or factories.

Which One Do You Need?

Before you make that decision, ask yourself a few questions.

  1. Budget – Get the finish you can afford. Polyurethane is cheaper.
  2. Indoor or Outdoors – For indoor floors, use epoxy. For outdoor floors, use polyurethane.
  3. Surface You Will Paint – Use polyurethane for decorative, kitchen, or dining surfaces as it offers a more decorative finish. For concrete floors in your garage, use epoxy.
  4. High-traffic Areas – For surfaces exposed to heavy weights, such as cars, use epoxy as it can withstand more weight than polyurethane. However, for patios or walkways, use polyurethane because it’s more flexible.

Related Read: Can You Put Epoxy Floor Over Paint?

Using Polyurethane Over Epoxy

You can use polyurethane over epoxy. You will get a hard, strong, durable, and flexible finish. Since epoxy has better paint adhesion, you can apply it first and then seal it.

Epoxy is stronger and can be a great undercoat option. When it cures, you can seal it with 1-2 coats of polyurethane to make it resistant to water, moisture, scratches, and UV lights.

So, if you apply polyurethane over epoxy, you will get a durable finish that is strong enough to withstand heavy weights. But, also flexible enough to cope with temperature changes. So, it’s the best of the two worlds.

Tip: The best polyurethane to use over it is oil-based polyurethane.

Final Words

The main difference between these finishes is the flexibility of polyurethane and the rigidity of epoxy. Polyurethane is more flexible and can cope with temperature changes; this makes it ideal for outdoor surfaces. While epoxy has a harder and more durable finish, it is ideal for indoor surfaces such as basement floors.

However, you can apply polyurethane over an epoxy finish to get the features of both sealants. 

Tony Adams
Tony Adams

Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,

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