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Does Epoxy Stick to PLA? A Detailed Explanation

Epoxy is one of the most durable, long-lasting adhesives available on the market, and many people use it to glue pieces of 3D prints together or to seal up the inside of their printed objects. However, epoxy doesn’t stick to everything, which begs the question – can you use epoxy on PLA?

Epoxy sticks to PLA. PLA is porous enough that the epoxy creates a solid bond with it. Because epoxy works so well with PLA prints, it is ideal for gluing your prints together or sealing them. 

The rest of this article will explain how epoxy sticks to PLA materials, the different kinds of epoxy, and how each epoxy type works. 

What Materials Does Epoxy Stick To? 

Epoxy is a highly reactive and thermosetting compound called epoxide. That means that when exposed to air and differing temperatures, its form and properties change quickly due to a chemical reaction.

Epoxy sticks to various materials, including PLA, PETG, ABS, wood, glass, and aluminum. However, it won’t stick to nylon, TPU, polyethylene, polypropylene, Teflon, and certain kinds of plastics. 

It’s commonly paired with a curing agent that triggers the hardening of the epoxy, which results in a strong adhesive.

Epoxy works as an adhesive by penetrating the pores of a material’s surface and bonding with it. So, if your filament or print is not porous enough, the epoxy will peel straight off. 

When they cure on a suitable object, epoxy bonds are powerful, which is why once the epoxy has solidified, it’ll be nearly impossible to break apart the pieces that you’ve stuck together.

The curing or hardening period can either be rapid (a few minutes) or take a while (up to 24 hours), depending on the type of epoxy you use and the temperature in the surrounding environment.

However, since epoxy hardens as it dries, it’s not advisable to use epoxy on pliable surfaces, as the cured epoxy will make the applied areas solid and prone to breaking when stretched. 

Also, if the material isn’t strong enough, stretching can cause it to become brittle and break.

What Are Different Types of Epoxy?

The different types of epoxy are pure epoxy, polyester resin, and epoxy acrylates. Understanding how each type of epoxy works will help you choose the kind that’ll work best with specific types of materials.

So, let’s look at these adhesives and discuss their optimal applications when you’re sticking with PLA: 

Pure Epoxy

Pure epoxy is probably the most common type you’ll find on the market. It’s epoxy resin and a hardener or curing agent. When using this type, you’ll need to mix the epoxy resin with the hardener before applying it to the surfaces that you need to stick together.

It typically has a more extended curing period, which means that it’s not the best type to use in cooler environments (because this will make the curing period even longer). 

A tip when using this type of epoxy: turn up the heat around the material you’re sticking together to hasten the curing process.

However, one primary advantage to the slow curing process is that this type of epoxy isn’t prone to shrinking as it hardens. Because of this, the epoxy doesn’t pull on the PLA when curing. 

Take note that some materials are more susceptible to disfigurement or pulling (such as when they are too thin) and will, therefore, benefit more from this type of adhesive. 

Another advantage to this epoxy type is its high adhesive strength. So if you’re looking for something that can handle not just your PLA prints but even concrete, brick, or even metal, this is the one to reach for. 

It’s also less prone to cracking and more resistant to moisture, making it more durable than other types of epoxy.

Polyester Resin

Remember not to confuse epoxy resin with polyester resin – they’re two completely different things. 

Polyester resin is a polymer that cures through a process called polymerization. Polymerization expedites the curing process, making it more convenient for quick uses, such as in model drafts or sample prints. 

However, unlike pure epoxy, it gives significantly lower adhesive strength, so it should be used more as a temporary hold and not for final prints that you intend to stay intact. 

Moisture can easily permeate through the polyester resin, making it easy to crack or break.

Moreover, if you’re particularly sensitive to strong odors or working in a place with poor ventilation, you should stay away from polyester resin as it gives off a pungent smell. Note that the smell may remain long after the resin has cured. 

Epoxy Acrylate

The third type of epoxy is epoxy acrylate, also called UV resin. While the polyester resin is a polymer, the epoxy acrylate is an oligomer that results from polymerization. Epoxy acrylate is commonly touted as the best type of epoxy, as it combines the best features of pure epoxy and polyester resin in one product.

It can provide high adhesive strength, making for a longer shelf-life and less maintenance. Also, it’s not water permeable and isn’t prone to cracking or becoming brittle over time. 

Despite this, it doesn’t take long to cure, which is very convenient when producing large volumes over a short time.

Epoxy acrylates also have high chemical resistance, making them suitable for highly acidic materials or materials prone to exposure.

However, unlike pure epoxy, epoxy acrylates cure when exposed to ultraviolet light or with the use of a thermal beam. They also generally cost a lot more than the two previous types of epoxy, so they’re not ideal for a simple DIY project at home.

This type of epoxy is more suitable for business use or industrial productions that require high strength, durability, and resistance.

Conclusion

You can use any epoxy with PLA since PLA has a rough texture that lends itself well to adhesives.  

You should reach for pure epoxy or epoxy acrylate for high durability and firm hold. However, epoxy acrylates tend to cost significantly more and are better for professional use. 

On the other hand, if you’re looking for something to use in sample prints, drafts, and even as a temporary fix, you can opt for the cheaper polyester resin instead.