PETG is an immensely popular 3D printing filament, widely used for its high strength, relative flexibility, and temperature resistance compared to the ever-popular PLA.

It’s relatively easy to print, even on budget printers without enclosures. It’s perfect for practical parts that need a little bit more give before breaking than PLA can offer. Thanks to its mechanical properties, it has displaced ABS as the second most popular 3D printing filament on the market.

But what exactly is PETG? What are the best applications for it? And how the heck can we get this sticky mess printing well? We’re going to answer all those questions and more, so let’s get started with the basics.

What Is PETG?

PETG stands for glycol-modified polyethylene terephthalate. It’s similar to PET, which is used to make disposable plastic bottles, but glycol is added to aid in extrusion and printing characteristics (e.g. reducing shrinkage). Thanks to the glycol, PETG is much easier to print.

In terms of mechanical properties, the material has moderate temperature resistance: ~45 °C maximum continuous operating temperatures with low creep, depending on load. It also has moderate impact resistance, moderate ultimate tensile strength, and moderate flexibility. This makes it a good all rounder compared to PLA and ABS.

PETG is also a moderately hygroscopic material, meaning it absorbs moisture from the air. While its hygroscopy can be worse than PLA, it’s nowhere near as hygroscopic as materials like nylon.

Applications

Thanks to its mechanical properties, PETG is a material suitable for functional prototyping or end-use parts. Although it falls short compared to ABS, it redeems itself through its much more forgiving printability. For example, an enclosure isn’t required to achieve PETG parts with good mechanical properties.

PETG is often used for 3D printer parts (especially for open-air printers), parts for small robots, and for jigs and mounts. In such functional applications, parts might be exposed to slightly elevated temperatures and therefore need to exhibit low creep over long periods to remain operational.

Another interesting application of PETG is to print highly transparent printed parts. As natural PETG is transparent, this can be achieved by printing very slowly and overextruding to fill in inter-line voids to create a non-porous part, which prevents the scattering of light (which can result in cloudiness) and remaining optically clear.

Lastly, PETG is generally considered food safe, but you should check with the manufacturer to ensure that their processing conforms to food safety standards. Check out our article on food-safe filaments for a few PETG options that fit the bill. If you plan on printing kitchen items with PETG, be sure your printer, extrusion system, and nozzle (avoid brass) have been cleaned thoroughly.