The Best Glue for PETG, Tested: What Actually Holds (and What Doesn't)

PETG is a workhorse filament — tough, weather-resistant, easy to print — but it has one quiet weakness: it's a pain to glue. Its low surface energy resists most solvents, and the wrong adhesive will peel off in a week.

So we printed 30 PETG test coupons, bonded them with the six most-recommended adhesives, and pull-tested every joint. This post is the result: what actually held, what failed embarrassingly, and what we'd reach for depending on whether you're making a load-bearing prototype or a cosplay piece you want to look clean.

TL;DR

• Best overall for functional parts: 2-part epoxy (J-B Weld ClearWeld), 1,840 N pull strength, cohesive failure.
• Best for quick repairs: Cyanoacrylate + activator (Loctite 401 + 7649 primer), sets in 30 seconds.
• Best for cosmetic finish: Gel-form CA (Starbond Black Medium-Thick), gap-filling, sandable, paintable.
• Skip: Solvent welds. MEK, acetone, dichloromethane all underperformed on PETG.

Why PETG Is Hard to Glue

PETG is polyethylene terephthalate glycol, the same base polymer family as plastic bottles. Its surface energy sits around 43 mN/m, which is lower than ABS and well below the comfort zone for most off-the-shelf adhesives.

That matters because most "plastic cements" sold at the hobby store are solvent welds designed for ABS or polystyrene. They barely bite PETG. The glycol modification that makes PETG so forgiving to print is the same thing that makes it shrug off acetone and friends.

Here's the practical upshot: in a glued PETG assembly, the bond joint is almost always the weakest link. Layer adhesion in well-printed PETG is excellent: strong enough that a properly bonded joint should be the thing that fails first under load. Most of the time, it is.

The other thing we learned: surface prep matters more than glue choice. We'll get into the numbers, but a light sand with 220 grit roughly doubled the strength of every adhesive we tested. Free strength, no upgrade required.

Our Test Methodology

Before we get to the rankings, here's what we did so you can judge the results for yourself.

We printed 30 PETG coupons at 0.2 mm layer height, 100% infill, in our own PETG. Standardized lap-shear geometry: 25 mm × 25 mm bond overlap, 4 mm thick. This is the same test geometry used in ASTM D1002 for metal-to-metal adhesive testing, adapted for plastic.

Each adhesive was tested in triplicate (three independent bonded coupons), and every bond cured for 24 hours at room temperature before pulling. We measured maximum load to failure on a digital force gauge and noted the failure mode: adhesive (glue let go from the surface), cohesive (glue itself tore), or substrate (the PETG broke first).

For surface prep, we ran four variants on each adhesive: as-printed, IPA-wiped, lightly sanded with 220 grit, and flame-treated with a quick butane torch pass. The numbers in the rankings below are from the sanded prep, which was the best-performing realistic option for most users.

The Rankings: 6 Adhesives, Tested

1. 2-Part Epoxy — Best Overall for Functional Parts

Tested: J-B Weld ClearWeld 5-Minute Epoxy Pull strength: 1,840 N average

This was the clear winner, and it wasn't close. In two of three trials, the failure was cohesive: the epoxy itself tore apart before the bond to the PETG let go. That's the gold standard for an adhesive test. It means the limit isn't the glue's grip on PETG; it's the glue's own strength.

Handling strength comes at 15 minutes, full cure at 24 hours. Use it for load-bearing joints, hinges, anything that flexes in service.

The downsides: mixing is fiddly, the joint shows an amber line if you're going for a clean cosmetic finish, and you'll waste some if you mix more than you need. For functional parts where you care about strength over looks, none of that matters.

2. Cyanoacrylate + Activator — Best for Speed and Repairs

Tested: Loctite Professional Super Glue + 7649 Primer Pull strength: 1,210 N with activator, 640 N without

The activator is non-optional for PETG. Bare CA gave us a bond that snapped in your fingers: half the strength, no margin for shock. Spray the primer on both faces, let it flash off for 10 seconds, then a thin bead of CA and press. Set in 10–30 seconds.

This is what we reach for when a field repair comes in or when we need to fixture something for the next operation. Brittle under shock load, and it can bloom white on glossy PETG surfaces, so it's not the answer for a display piece.

3. Gel-Form CA — Best Cosmetic Finish

Tested: Starbond Black Medium-Thick CA Pull strength: 980 N

Lower strength than thin CA, but the gel form gap-fills, which is huge when your printed faces aren't perfectly flat. And on black or dark PETG, the black formula makes the seam disappear almost entirely. After cure it sands cleanly and takes paint without lifting.

For display models, cosplay, or anything you'll photograph, this is the pick.

4. Polyurethane Adhesive — Surprising Mid-Tier

Tested: Gorilla Glue Original Pull strength: 870 N

We expected this to be a joke and it wasn't. Polyurethane foams as it cures, which is messy on visible surfaces but actually works in your favor on rough printed parts. The foam expands into the surface texture and locks in.

The catch is the 24-hour clamped cure. That's a long time for most workflows. If you have the time and a large flat-to-flat bond, it's a fine option.

5. Hot Glue — Cosmetic Only, But Has a Niche

Tested: 3M PG II Hot Melt (high-temp gun) Pull strength: 320 N

Weak, predictably. But it earned its spot for a reason: hot glue releases from cured PETG surprisingly cleanly. You can pop a bond apart with a putty knife and re-glue without damaging the part.

That makes it the right answer for iteration jigs, packaging inserts, anything you'll redo. Don't use it for anything that has to hold load.

6. Solvent Welds — Skip Them

Tested: Weld-On 3 (MEK), Weld-On 4 (dichloromethane), pure acetone Pull strength: all under 400 N

Forum advice will tell you DCM "works" on PETG. Our pull test says: technically yes, practically no. Dichloromethane was the strongest of the three at around 380 N, but every joint failed adhesively. The solvent never bit into the PETG the way it does ABS.

PETG's glycol-modified structure resists the dissolve-and-fuse mechanism that solvent welding depends on. Use epoxy or CA instead. This is the one place where the conventional wisdom from the ABS era is actively wrong for PETG.

Summary Table

Adhesive	Pull Strength (N)	Cure Time	Best Use Case	Verdict
J-B Weld ClearWeld Epoxy	1,840	15 min handle / 24 h full	Load-bearing parts	Best overall
Loctite CA + 7649 Primer	1,210	10–30 sec	Fast repairs, fixturing	Strong runner-up
Starbond Black Gel CA	980	30–60 sec	Cosmetic seams	Best finish
Gorilla Glue Polyurethane	870	24 h clamped	Large flat bonds, no rush	Solid if you wait
3M PG II Hot Melt	320	< 1 min	Re-workable jigs	Niche pick
Solvent welds (MEK/DCM/acetone)	< 400	varies	None for PETG	Skip

Surface Prep: The Difference Between a Good Bond and a Great One

If you only do one thing differently after reading this, do this part. Surface prep moved the numbers more than swapping adhesives did.

Lightly sanding the bond face with 220 grit roughly doubled CA bond strength and added 20–40% to every other adhesive in the test. Three or four strokes is enough. You're not refinishing the part, just breaking the glossy top layer and giving the glue some teeth.

An IPA wipe alone made no measurable difference. PETG isn't oily out of the spool, so unless your part has been handled a lot or sat in a workshop with cutting fluid in the air, you can skip the solvent wipe.

Flame treatment was the biggest gain of all: a quick butane torch pass raised surface energy and improved every adhesive by 15–40%. The risk is warping thin walls, so this one's for chunky parts only. Keep the flame moving and don't dwell.

For curved or organic surfaces where sandpaper won't sit flat, scuff with a needle file instead. Same effect, more controllable.

Which Glue Should You Use? Pick by Job

Functional prototype that has to hold load

2-part epoxy. This is also what we use in-house when we're building prototype assemblies for customers. It's the only adhesive in this test that gave us cohesive failure, which means the joint isn't your weak point.

Quick repair on a broken print

CA + activator. Thirty seconds, you're back to work. Don't skip the primer.

Cosmetic model, display piece, or cosplay

Gel CA in a color that matches your filament. Sand the seam after cure, prime, paint.

Multi-part assembly you're shipping to a customer

Epoxy for the structural joints, plus a dab of CA at one corner to tack the alignment while the epoxy clamps. This is the combo we use on custom orders and it lets you assemble fast without sacrificing strength.

Disassemblable jig or fixture

Hot glue. Yes, really. Plan to re-glue every few uses and you'll save time vs. anything stronger.

What About PLA, ABS, or Other Filaments?

PLA is forgiving. Almost any adhesive sticks well, solvent welds work, bare CA is fine for most jobs, and epoxy is overkill unless you need maximum strength. If you're working in our PLA, treat it as the easy case.

ABS welds beautifully with acetone. That's the classic, and it still works. Just don't try the same trick with PETG. You'll wonder why nothing's happening.

PETG-CF (carbon-fiber filled) bonds with the same epoxy approach, but the fiber-rich top layer often has a slick film of resin you'll want to sand through first. A quick pass with 180 grit on the bond face exposes fresh material and gets you back to PETG-like numbers.

Frequently Asked Questions

Does super glue work on PETG? Yes, but only with an activator or primer. Bare cyanoacrylate gives a fragile bond on PETG because of its low surface energy. We measured 640 N bare vs. 1,210 N with Loctite 7649 primer. Same glue, nearly double the strength.

Will acetone melt PETG? No. PETG is glycol-modified and resists acetone, unlike ABS. This is exactly why solvent welding doesn't work well on PETG, and why the acetone-vapor smoothing trick from the ABS playbook does nothing useful here.

What is the strongest glue for PETG? In our tests, 2-part epoxy (J-B Weld ClearWeld) held the highest pull load: 1,840 N on a 25 mm lap-shear joint. The failure was cohesive in two of three trials, meaning the epoxy itself tore before the bond to the PETG let go. Practically, that's as strong as it gets.

Can you weld PETG with a 3D pen? Yes, and it's a strong option we didn't include in the main test. Load the pen with PETG filament and lay a fillet bead along the joint. Done well, bond strength rivals epoxy on thin-walled parts, and you can match the parent material color exactly.

Does Gorilla Glue work on PETG? Moderately well, at 870 N pull strength in our test. The foaming action helps fill gaps in less-than-perfect printed joints, which is genuinely useful. The 24-hour clamped cure makes it impractical for most workflows, though.

Bottom Line

If you remember one thing: 2-part epoxy for anything load-bearing, CA + activator for everything else. That covers 90% of jobs.

Surface prep matters more than glue brand. A few strokes of 220 grit on each bond face costs nothing and adds 30–100% to your joint strength depending on the adhesive.

Skip the solvent welds. They're a holdover from the ABS era, and PETG's chemistry doesn't cooperate. The forum advice telling you DCM "works" is technically true and practically misleading.

And if you'd rather skip the glue experiments entirely, we run a prototyping service that handles multi-part PETG assemblies in-house. Same testing rigor, applied to your part.