When you need to bond a couple of pieces of plastic together for either professional, creative or utility purposes you’ll need an adhesive.
There are multiple forms of adhesive for plastics and some of them require external forces like heat to allow them to work.
Some of the most widely available adhesives that can chemically or cohesively bond two pieces of plastic are epoxies.
An epoxy adhesive is perfect for industrial and hobby purposes.
With a good epoxy you’ll be able fix the hull of a boat and attach a Warhammer figurine to its base.
Why Use an Epoxy?
You may be wondering why should you choose an epoxy adhesive over an acrylic adhesive like your household superglue?
Well, there are a few reasons but immediately we can look at the bond strength of each.
Epoxy adhesive is the strongest reactive adhesive on the market and can have a tensile strength almost double that of acrylic adhesives.
Epoxy adhesives don’t malform or shrink during curing, so they are great gap fillers.
Acrylic adhesives aren’t compatible with some plastics and can actually be corrosive.
Epoxies work well with most plastics; however some plastics can just reject the bond so check the label to make sure.
Epoxies are simply a better adhesive compared to cyanoacrylates (like Crazy glue), but they take longer to cure, so they might not be the best option for a quick job.
How Does an Epoxy Work?
Epoxies work because they are a reactive adhesive.
They chemically react with the surface that they are applied to, and when hardened, create strong polar bonds.
To harden an epoxy adhesive requires a hardening catalyst or hardener.
This means that all epoxy adhesives can be used to fill large gaps instead of just bonding two surfaces.
After the two parts of an epoxy have been mixed you usually have a working window (aka a pot life) within which the adhesive will not fully harden.
During that window, you can apply it to the surfaces or mold it to the necessary shape (you can get moldable epoxies – I’ll go into that a bit more later).
Once an epoxy has been applied you have to wait for it to harden, and then once it hardens, you’ll need to wait for it to cure.
This curing time allows your newly created bead of epoxy to completely harden and hold its shape, essentially creating a bead of hard plastic.
Once cured though, epoxy can be sanded, drilled, sawed, and painted.
It is highly heat resistant and unreactive with the weather so is ideal for outdoor use.
Each brand and type of epoxy has its own setting time and curing time, so make sure you read the packaging carefully to ensure you don’t waste any.
Depending on the intended use of the epoxy you might want one that either sets quicker, cures faster, can be shaped easier, or is a specific color.
Epoxy adhesives are versatile enough that you are sure to find one that meets your requirements fairly easily.
I’ll go over some of the best options currently available and which one may be better for your specified use.
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In a Rush?
Have you got a trip to the lake coming up soon and you’ve found a small crack in your kayak?
Not to worry. I’ve got my top pick right here with just a few reasons why I love it.
This epoxy is a great adhesive from a great company. With plenty of working time and a decent curing time, this epoxy will fit most of your needs.
- Easy-to-use, two-barrel extruder.
- Five-minute set time.
- Strong enough for external automotive applications.
- Works on steel, aluminum, glass, wood, ceramics and importantly most plastics.
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This two-part epoxy from Gorilla is great for almost any adhesion task you might need to carry out.
Gorilla has rated it for use on small appliances, large indoor projects, and even automotive repairs.
The dried product is weatherproof, heatproof up to 185°F and extremely durable to wear and tear.
It is also solvent resistant when dry, so make sure to clean up any spills or overfills during the curing process.
Most two-part epoxies will share a similar tensile strength, but this one comes out at above average in terms of strength.
It sets in five minutes and cures in 24 hours, so you’ll have plenty of time to apply the epoxy and maneuver the pieces being adhered before you’ll have to worry about your epoxy drying.
This also gives you the right amount of time for setting, in that you won’t need clamps or grips to keep the pieces of material fused together.
The five-minute set time means you only need to keep the pieces together for that long, and then you can walk away from your project and leave it to cure for 24 hours.
All two-part epoxies on this list will require a 1:1 ratio of hardener to solvent, which can be tricky to measure out in small volumes.
Gorilla has implemented a two-barrel syringe that by design extrudes an equal amount of each, removing all stress from yourself to measure out the exact quantities.
With the syringe design you also get an included cap that fits over both heads.
As long as you clean the nozzles after each use this epoxy from Gorilla will keep working for a couple of years.
The nature of this epoxy allows it to act as a gap filler, meaning that large cracks or gaps won’t be an issue to you.
The fact that it dries to the hardness of a tough plastic means that you can replace structurally integral parts with this epoxy and rest assured that it’ll hold.
The epoxy also dries clear, which is perfect for projects where you want to hide the joint or adhesion point.
It is also sandable, drillable, and paintable so you can hide it in plain sight.
You get 0.85 fluid ounces of epoxy (when mixed), which is enough to fill in larger gaps.
The only plastics this epoxy isn’t rated for are polyethylene and polypropylene.
These plastics are reactive with the solvent and can cause uneven adhesion, or the solvent in the epoxy could cause wear on the plastic.
- This epoxy offers an extremely strong, permanent, gap-filling solution to household needs.
- With a set time of five minutes, this is ideal for quick repair jobs.
- The easy-to-use, two-barrel syringe takes the pressure off of you to mix the parts in exactly a 1:1 ratio.
- The included cap and separating tubes keep the epoxy useful for a couple of years.
- The versatility of the dried product makes this epoxy ideal for standard and nonstandard uses.
- Can take some practice to get the application of the mixed product exactly right.
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This two-part epoxy from Loctite works almost identically to the epoxy from Gorilla.
Loctite has over 50 years of experience in adhesives, and it really shows in this epoxy.
You only get 0.47 fluid ounces of epoxy in this syringe, so it may not be amazing for larger gluing jobs.
Similar to the Gorilla epoxy, the Loctite version has a five-minute setting period and 24-hour curing period.
However, with a maximum set strength of 3,200 psi, this epoxy falls slightly short of the high standards already set.
You are able to bond all types of material with this epoxy ranging from metal, glass, ceramic, wood, many rigid plastics, china, tile, fiberglass, concrete and even to stone.
This epoxy is ideal for smaller projects – more specifically for visual uses like in small-scale modeling.
(See some of the most in-demand model kits here.)
Loctite includes a precision tip with the epoxy that you can attach to ensure you only apply your mixed epoxy to the desired areas.
You still get the same two-barrel syringe extruder design that was useful in the Gorilla epoxy.
Loctite gives you two of the precision-nozzle heads to make sure that you can still use this feature even if one of the nozzle heads gets blocked by dried epoxy.
This epoxy dries clear, so you don’t have to worry about it standing out.
Interestingly, Loctite states that this epoxy can actually be tinted before application to ensure you get the correct color.
If you use epoxy pigment, you won’t have to be concerned about changing the composition of the epoxy. It will still set and cure in the same amount of time.
The fact that you can customize the epoxy and still sand, drill, and paint it makes it perfect for miniature modeling in things like Warhammer or even precise-scale airplane modeling.
- You get an easy-to-use two-barrel design that helps to mix the epoxy in the perfect ratio.
- Loctite includes two precision-nozzle heads that allow you to apply the epoxy in much smaller areas.
- The epoxy sets fast (five minutes) but not so fast that you’ll have to rush the placement.
- The epoxy is strong enough to be sanded, drilled, and painted.
- You can mix pigments into the epoxy before application to make it more visually suitable.
- You only get 0.47 fluid ounces per syringe, so you may need multiple packs for larger jobs.
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The PlasticWeld epoxy putty from J-B Weld is the first putty on our list.
Epoxy putty works identically to the liquid version of epoxy adhesive except that it is completely workable and shapeable before application.
It also has a much longer working time and a much shorter curing time, but this basically means that it won’t achieve as high a tensile strength.
Because the putty comes slightly mixed before use you have a shorter shelf life once opened.
Instead of having to worry about mixing the epoxy with the hardener in a perfect 1:1 ratio, J-B Weld has packaged both putties together.
You simply have to mix both components into one solid mass of uniform color, and this is when the epoxy’s pot life/setting starts.
You have around half an hour of working time so don’t worry about rushing to mold and place this epoxy haphazardly.
You can use the putty to sculpt landscape or to fill in larger spaces in a damaged car bumper.
It adheres instantly but remains malleable for up to 30 minutes after mixing.
As with the other epoxies, this one can be sanded, cut, drilled, and painted for whichever finish you’re going for.
It cures to an off-white color, so you can apply any paint over top and it will take it fairly easily.
It also is completely waterproof and mostly heat resistant once cured, so it is ideal for external applications.
As this is still an epoxy, it is recommended to use gloves when working the putty as it can be slightly corrosive.
- It comes premixed so you don’t have to measure quantities.
- It is completely moldable and shapeable after mixing.
- The epoxy cures relatively quickly compared to liquid epoxy (~3 hours).
- Just like the other epoxies, this one is sandable, drillable, and paintable once cured.
- You get about 2 ounces of putty per package, which is perfect for larger jobs.
- Once used this epoxy has a shorter shelf life as you cannot avoid mixing some of the unused epoxy with its hardener.
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This epoxy from Devcon is extremely similar to our number one pick and works almost as well.
You get 0.84 fluid ounces per syringe, and it can be used to adhere most materials.
As with the other epoxies, you will have a tough time bonding polyethylene and polypropylene.
It almost matches the Gorilla Two-Part Epoxy in tensile strength at 3,200 psi and is great for most indoor and outdoor applications.
The epoxy and hardener come packaged in a familiar way (two barrels, single plunger, and extruder), which removes the need for you to measure out the two components.
The major difference between this epoxy and the other two liquid epoxies is in its application.
The Devcon epoxy is water resistant even before curing, meaning you can use it in less-than-ideal weather conditions.
This epoxy also gives you a bit extra working time, allowing you 15 minutes before it sets.
This means you can take a step back, make sure your bond is perfect, and make small adjustments if necessary.
- Extremely high durability and tensile strength.
- The setting time allows you 15 minutes to make small adjustments.
- Water resistant before and after curing.
- The two-barrel syringe extruder helps to mix the components in the correct ratio for you.
- No included cap for multiple uses.
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This two-part, quick-setting epoxy is the second entrant on the list from J-B Weld.
Just because this is the last entrant to our list does not by any means mean that it is a bad epoxy.
This is actually a great epoxy for quick jobs, and J-B Weld boast a large amount of features that make it good.
Just as with the other high-end epoxies, you get 0.84 fluid ounces of epoxy per syringe, and you get the commonplace two-barrel syringe design.
The PlasticWeld Quick-Setting Epoxy comes with a no-waste, resealable cap that ensures proper application and the best option for long term storage.
A huge selling point for this epoxy is its quick setting and quick curing time.
J-B Weld claims that this epoxy sets to full hardness is an hour and sets with a tensile strength of 3,900 psi, which is a huge figure.
- Sets quickly and cures quicker than any other epoxy on the list.
- It has an extremely high tensile strength.
- Comes with two-barrel extruder design for precise measurements.
- Has a resealable cap that twists into place.
- The fitted cap blocks attachments like mixing tubes.
When using an epoxy to bind plastics you need to take a few extra precautions and do some preparation to ensure you get a solid bond.
Epoxies work amazingly well for binding most materials as they don’t require specific conditions to set and can set as quickly as five minutes.
Certain plastics, like polyethylene and polypropylene, won’t take to the adhesion of an epoxy as they don’t chemically bond.
If you’re looking for something to bind these plastics, an acrylic adhesive or urethane adhesive will almost always work better.
You can tell which type of plastic you’re trying to bond by looking for the recycling triangle.
If it has a PE or PP written inside the triangle, then epoxy will not work.
Performing a test on small pieces of the plastic is always recommended regardless of which type you’re using.
Before you mix and apply your glue, there are a few things you’ll need to do to ensure the most secure bond.
The last thing you want is to be paddling in the middle of a lake and that old crack starts to leak again.
- Clean the surfaces to which you’ll be applying the epoxy. Use dish soap or a rubbing alcohol to ensure there is no grease or build up.
- Rough up the surface with some sanding paper, steel wool, or chemical activator.
- Mix the two parts of your epoxy together. If you’re using a putty, start to knead the putty.
- If you’re trying to stick a very precise area, use some masking tape and a small brush to apply the adhesive.
- Before the setting period is up make sure to clean any excess epoxy off before it cures as you’ll be chipping away at it with a hammer and chisel once it hardens.
- If you can clamp the two components together, you’ll be ensuring the most secure bond. The more your components are held together during cure time, the more securely they’ll be bonded.
If you’ve followed this guide, you’ll almost assuredly be able to stick anything together.
Epoxies are some of the best adhesives out there, so take care while you use them. You don’t want your five fingers to become one flipper.