Food-Grade 3D printing: Is PETG Food-Safe?

Desktop FDM 3D printers are amazing machines that enable people to bring all kinds of plastic objects and tools into existence, from brackets and replacement parts, to figurines, to household goods. But while you technically could 3D print many things for your home—including a plate, fork, or coffee cup—the question is: should you?

There are special considerations for any product or object that is intended to come into contact with food. It makes sense. You don’t want products in your kitchen to leach toxic chemicals into the food you eat and you don’t want innocuous kitchen items to become a breeding ground for potentially harmful bacteria. In this article, we’re looking specifically at PETG filament and answering the question: “is PETG food-safe?”.

What is PETG?

Let’s start with the basics. PETG, or Polyethylene terephthalate glycol, is a thermoplastic material from the polyester (PET) family. If you haven’t heard of PET, you will undoubtedly have come into contact with it. The plastic is one of the most widely used in the world: for instance, 70% of bottled drinks (like soda, juice, water) are packaged in PET bottles.[1] PETG shares many characteristics with PET but differs due to the addition of glycol. The glycol makes PETG stronger, more durable, and more impact and temperature resistant than regular PET.[2]

In a 3D printing context, PETG is among the most popular filaments. It combines the aforementioned properties (strength, durability, resistance) with good printability. If we look at PETG compared to other ubiquitous filaments, it is stronger and more resistant than PLA filament and easier to print than ABS. It is also competitive in terms of cost.

Is PETG filament food-safe?

As a raw material, PETG is considered food-safe. This means that there are no toxic chemicals or ingredients in the pure polymer that will contaminate food or pose a danger to humans.

That being said, there are other factors that can influence how food-safe PETG filament actually is. As we’ll see below, things like additives in the filament, porosity in the 3D printed component, and contaminants on your 3D printer can determine whether or not your PETG print can safely come into contact with food. In short, the material PETG is food-safe, but a printed part made from PETG may not be.

Recommended reading: Food-Grade 3D Printing: Is PLA Food-Safe?

What are the food-safe risks of PETG?

There are important reasons that kitchenware manufacturers must follow and meet food safety standards. Any lapses can cause food poisoning and serious health problems for consumers. The same is true for objects you 3D print at home: any missed precaution can have negative outcomes. Here are the three main food safety risks associated with PETG 3D printing filament that you should be aware of.

1. Gaps or holes in 3D prints can become breeding grounds for bacteria

You may think your 3D print is solid when you remove it from the print chamber, but FDM 3D prints are almost always porous. Tiny gaps between layer lines and cracks invisible to the naked eye can quickly become breeding grounds for harmful bacteria. You may also feel assured that washing your 3D print with dish soap would decontaminate it after food contact, but it can actually lead to more moisture trapped inside the part. With a glass transition temperature of about 85°C, PETG is not able to withstand very high temperatures and cannot be sterilized using boiling water (100°C). 

Additives and dyes in PETG filament can affect how food-safe it is

2. 3D printer can contaminate PETG filament

3D printer filament is not the only consideration when printing a custom cookie cutter, bowl, or spork. The 3D printer itself must also be taken into account, particularly the nozzle. Nozzles can become clogged with debris from other 3D printing filaments as well as dust and dirt. Particles from this buildup can contaminate fresh PETG filament as it is melted and passes through the extruder. This is particularly risky if you have previously 3D printed non-food-safe filaments. 

The nozzle material is also important. Brass nozzles are prone to wear and can leach toxic substances into your 3D print. Some of the cheaper brass nozzles have even been found to contain trace amounts of lead, which is highly toxic to humans. Finally, if you are using a glue or hairspray on your print bed to improve first layer adhesion and avoid warping, that can also increase the food safety risk.

3. Additives in PETG filament can contaminate food

While PETG is considered a food-safe material, many filaments contain additives that can reduce the purity of the thermoplastic. If those additives are not themselves food-safe, your PETG filament could no longer be safe for food handling applications. For example, some filament dyes are made from non-food-safe chemicals. It is therefore a good idea to look for additive-free filaments, virgin filaments (i.e. undyed), and PETG filaments that are officially labeled as food-safe.

Recommended reading: How PETG melting point influences 3D printing

How to ensure food-safe 3D printing?

Fortunately, there are measures you can take—both in the pre-printing and post-processing stages—to minimize and even eliminate the potential health risks of your 3D printed objects coming into contact with food.

1. Use an FDA approved food-safe filament

One of the first things you can do to help ensure your 3D print will be food-safe is to invest in an FDA-approved food-safe brand of filament. This certification not only guarantees that there are no additives or dues in the spool of filament that will pose any health risk if they touch food, it also guarantees the filament was safely manufactured at a clean manufacturing facility that meets industry standards. There are various options when it comes to FDA-approved food-safe PETG filaments—just have a browse online or ask at your local filament supplier. 

2. Use a food-grade nozzle

In addition to buying certified food-safe PETG filament, you’ll also want to invest in a 3D printer nozzle that meets food and health standards. As we said, your standard brass nozzle won’t cut it. Instead, invest in a nozzle made from a food-safe material like stainless steel.[3] As an added measure, don’t use the stainless steel nozzle with any non-food-safe filament. This will help to ensure that your 3D print is kept safe from any contaminants during the 3D printing process.

Applying a food-safe coating will ensure that your 3D print is watertight.

3. Treat 3D prints as single-use items

You can also reduce the risk of any food-borne illnesses by only using your 3D printed kitchenwares once. In other words, if you follow the first two tips, the part that comes off the 3D printer bed should be food-safe. Once food has touched it, however, there is a risk that particles of food or moisture will get trapped in the print’s porous structure, which can lead to bacterial or mold growth. It’s not a great option in terms of sustainability, but treating 3D prints as single-use items will minimize any potential contamination risks. 

4. Apply a food-safe coating to seal 3D prints

The best way to ensure your PETG 3D print is food-safe is to combine the use of an FDA-approved filament with a stainless steel nozzle and a food-safe coating. Applying a coating to the printed object will seal any cracks or pores, resulting in a watertight surface. This prevents food particles from finding their way into the 3D print and facilitates washing. 

There are a few different coating options, including epoxy resins or silicone coatings. When choosing a sealant, it is important to find one that is food-safe certified and to follow usage instructions closely. We should point out that because food-safe coatings wear down over time, you should not use your 3D printed part frequently over the long-term. For example, a novelty cookie cutter is better suited to printing than a food container you use and wash everyday.

Key takeaways

Ultimately, the answer to the question “is PETG food-safe” isn’t quite as simple as yes or no. Yes, PETG as a material is food-safe, but when 3D printing comes into the equation, it gets more complicated. Here is a summary of what we covered:

• PETG (Polyethylene terephthalate glycol) is a popular thermoplastic material that is itself food-safe

• Additives and dyes in PETG filament can negatively impact how food-safe the material is, so it is important to seek out FDA-approved food-safe PETG filament brands.

• 3D printed parts are prone to small gaps and pores that can become breeding grounds for mold and bacteria. Using a food-safe coating to seal 3D prints can prevent this from happening.

• Brass 3D printer nozzles can leach harmful chemicals into PETG 3D prints. It is therefore vital to swap to a food-safe stainless steel nozzle when printing food-safe PETG.

• Food-safe epoxy and silicone coatings can wear down over time, so 3D printed parts should not be in contact with food over the long term.

Resources

[1] https://www.recycletheone.com/what-is-pet

[2] https://www.twi-global.com/technical-knowledge/faqs/what-is-petg 

[3] https://formlabs.com/blog/guide-to-food-safe-3d-printing/