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Is PETG Hygroscopic?

Is PETG Hygroscopic? | 3D Printing Spot

Updated by

William Stone


January 13, 2023

PETG is one of the best and most widely used filaments in 3D printing. It has many qualities that make it ideal for any project, but is it Hygroscopic?

Though PETG has lots of great qualities that make it a  great choice for anyone who wants their 3D prints to be strong and durable in all but the most extreme of conditions. But If the filament absorbs water before being used, it can cause all sorts of problems both aesthetically and structurally, so is PETG hygroscopic?

Unfortunately, PETG is hygroscopic so you will need to be careful about the conditions it is stored in. Luckily, there are things you can do to preserve your PETG filament while not in use, so you can avoid dealing with any of the problems that come with its hygroscopicity.

PETG is very versatile, but damage that happens in storage can really affect the final product that comes out of your 3D printer. Learning more about what PETG is and what hygroscopic means can help you to better understand how to handle and store your filament. After all, your final print will be much better off if the filament you’re using is in tip top shape.

Over the years, I’ve worked with all of the most common materials used in 3D printing, including ABS, PLA and of course PETG. Through my experiences with these materials, I’ve had plenty of time to experiment with the best ways to store and maintain them. By the time you are done reading, you’ll be able to counteract all of the most common problems associated with the hygroscopic nature of PETG.

Table of Contents

What Is PETG And What's So Good About It?

PETG is one of the most commonly used materials in 3D printing, and there are plenty of reasons for that. Like most of the other materials used in 3D printing, PETG is a thermoplastic capable of being molded and remolded into any number of shapes and sizes. These properties are why thermoplastics are commonly used for 3D printing.

In addition to its thermoplastic properties, PETG has a number of qualities that make it favorable to use in all sorts of applications. PETG is very strong, resistant to impact and able to withstand high pressures,  so it will hold its shape in all but the harshest of conditions. It's chemical resistant so it has no problem being exposed to all sorts of harmful acids and bases, not to mention that if used correctly, any object you make with it will be waterproof. PETG is even resistant to heat and UV radiation, making it a great choice for any object that's going to be spending a lot of time outside and exposed to the sun.

All of these qualities plus PETG’s general cheapness to produce and buy make it no wonder that this material has taken over the world of 3D printing and is used in countless everyday products we use every day. It would be surprising if you didn’t have at least a few products made of PETG laying around your home right now.

Outside of 3D printing, PETG is heavily used in the packaging of food and drink products. PETG is non toxic and food safe, making it the perfect material for use in water bottles, take out containers and the packaging for any other consumable good that you can think of.

PETG is also often used in the medical industry, both in the packaging of medical devices and actual medical implants. The rigidness and strength of PETG allow it to withstand even the harshest of sterilization procedures, making the material perfect for anything that will be used in the medical field.

What Does Hygroscopic Mean?

Now that we know everything the PETG is resistant to and what it's used for, we can focus on one of the biggest drawbacks of PETG, the fact that it is Hygroscopic.

But what does Hygroscopic mean? Basically, if an object is hygroscopic, it means that the object will continuously absorb water from the air until it is fully saturated and unable to take on any more water. The opposite of this is hydrophobic, meaning that even if water is dumped on top of the material, it will not absorb and simply bead up and slide off the surface.

Saturated or water logged PETG filament can cause a lot of problems in the outcome of your prints. Firstly, PETG that's absorbed too much water may not lay properly causing mild dimensional differences in your print that you did not design. Water can cause some of the bonds in the PETG and its layers to break down, meaning that your print will be significantly weaker than it should be.

How Should You Store PETG?

As stated before, PETG is hygroscopic, meaning that it absorbs water from the air over time. This can cause all sorts of problems so it’s important to make sure that you are storing your PETG properly.

Since the main problem here is the absorption of water, moisture and humidity are your two biggest enemies here. Simply living in a particularly humid region of the world can make it a lot harder to successfully care for your PETG.

Because of this, you should store your PETG in an enclosed container in a cool and dry part of your home. Obviously, having a dehumidifier close by can help prevent your PETG absorbing moisture and the use of vacuum sealing and dry boxes can be useful here too. Though these are the ideal conditions for storage, if you don’t live in a particularly humid area, you don’t have to get too fancy. Just make sure that your filament is stored in the driest part of the house possible away from any possible sources of moisture.

How Do You Know If Your PETG Is Wet?

Though it’s not blatantly obvious that a spool of PETG is saturated with water just by looking at it, there are a few obvious signs that you’ll notice if you are using wet PETG to print.

First, you might notice that the quality of your print is getting worse and the layers of your print aren’t adhering to each other as well as they should be. It will be even more obvious if compared to a good print that you have laying around. If all else is the same but your print is of significantly lesser quality than normal, it is most likely that this is the issue.

Another way you can tell if by simply listening as you print. If you hear any sort of crackling or popping noises coming from the hot end of your printer, this is most likely water evaporating as the plastic is being melted. If you’re hearing these sorts of noises as you're printing, there’s no doubt that the PETG being used is too wet.

What Do You Do If Your PETG Is Wet?

Luckily, even though the absorption of water can cause a lot of problems for your PETG filament, it's not the end of the world if your filament gets wet.

Filament dryers can be used on entire spools of filament to get rid of all moisture that was absorbed. These machines are easy to use and allow you to make your wet PETG filament as good as new again. Two of the best filament dryers on the market are the Sovol SH01 Filament Dryer and the PrintDry Pro Filament Drying System. These filament dryers, along with many others, allow you to get around the hygroscopic nature of PETG so that you don’t have to be so worried about storing your PETG in the best conditions possible.


William Stone

William Stone

William has spent 20 plus years in the custom manufacturing industry as a COO, CEO and Owner of various custom product businesses. His experience has exposed him to all types of manufacturing from die cast, die struck, injection molding, CNC machining, laser etching, engraving and of course 3D printing.

Learn more about William Stone

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Is PETG Hygroscopic?

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