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FDM 3D Printing Materials Part 2: PETG

By Mitch

September 27th, 2023


Several spools of PETG filament on a white background
(Image: iStock)/Mitch)

What is PETG Filament?

In this article we’ll look at a different type of filament that you may well be aware of but haven’t yet used; PETG.


PETG (Polyethylene Terephthalate Glycol) is a durable, hard-wearing polyester combination that can be used as a filament in FDM 3D printing.


Now, here’s the science part!


PET was first formulated in 1941 by the British scientists Dickson and Whinfield who patented their product for the manufacture of fibres. These fibres were intended to replace cotton as a source material for uses in textile manufacturing. It did however take until 1946 for PETG to be settled into the industry but it is still widely used today.


By 1952 use of PET had expanded into food packaging in the form of transparent film and then in 1976 in the use of rigid drinks bottles. Drinks with low oxygen sensitivity were particularly best suited such as carbonated soft drinks, mineral water, and beer. The significance of this can’t be understated as it made PET the most used plastic in the world.


PETG itself is a copolymerisation of the original PET. The addition of ethylene glycol (the “G”) made the PET less prone to crystallization and reduced its melting point. It also had a better thermal stability allowing it to be used to create flexible extruded parts as made by FDM 3D printers.


Why choose PETG Filament for 3D printing?


A selection of different coloured plastic bottles
(Image: Adobestock)

As a printing material PETG has excellent flexibility, durability, and chemical resistance. This makes it an ideal choice for 3D printing enthusiasts who may want to try more than just model making.


That being said, it is still a good choice for those modellers who need good impact resistance and additional strength in their creations. It’s also great for models requiring snap together or movable parts.


The use of PETG filament in 3D printing is much the same as that of PLA (Polylactic Acid); particularly if you are mainly interested in producing models for display etc. However, due to the properties of PETG mentioned previously, it is ideal for producing usable parts for machinery, medical devices, food containers and drinks receptacles.


The most common uses of PETG for the hobbyist 3D printing enthusiast could include:


• Cups – PETG is water resistant

• Lunch boxes – heat resistance can help prevent wilted sandwiches!

• Key fobs – good strength properties are ideal for an everyday item

• Outdoor plant pots – temperature resistance and water resistance combined

• Small handheld tools – pliers or handles for saws can be ideally suited

• Moving parts for models – snap together parts or those needed for items such as RC cars etc.


The uses in prototyping are also plain to see as the above items show the durability of PETG and its strength as a printing material.



How do I choose PETG filament?


When deciding to buy or use anything, it’s always worth taking a look at the Pros and Cons. In the case of PETG that’s no different and there are a lot of things to consider before you decide if PETG is the right choice for your project.


Let's then take a brief look at both sides of the coin.


PROS

CONS​

Strength and resistance to impact

Can cause greater wear and tear to printer parts

Flexibility

Higher printing temperatures

Thermal resistance

Possible “stringing” issues when printing

Good adhesion between layers

Not ideal for supporting structures

Food grade

Can stick “too well” to build plates

Minimal deformation when printing

Can become brittle

Water resistance

Scratches more easily

Resistance to wear and degradation

Low odour

How to conserve PETG filament


Several rolls of different coloured PETG printer filament
(Image: Shutterstock)


With any product you might purchase external factors., you’re going to want to know how long it will last. Now for most people who are enthusiastic about 3D printing, a spool of filament might not last longer than 24 hours before it’s been used up! However, in this case, we’re not talking how much you use and how quickly but more about how long the integrity and quality of your PETG will remain intact.


Once you’ve purchased a roll of PETG it will have a natural shelf life of about 2 years under normal conditions. Atmospheric conditions and how well you store the filament will have an impact on that time span so keeping it stored correctly will be to your benefit. Damp, humidity or exposure to UV light and heat will have an affect on the quality of the PETG and in turn, the quality of your prints. Apart from trying to ensure your print workshop keeps the perfect environmental conditions, there are a few options available to you in terms of storage which will help you to avoid these external factors.


• Filament Drying Box: There are many of these on the market of varying types and cost and are basically electrical devices designed to dry and avoid humidity issues which may affect your filament. You could also make your own drying box and there are a few YouTube tutorials online to show you how.


• Vacuum Storage Bag: These are basically small, sealed bags specifically designed to fit a roll of filament and then use a vacuum pump to extract all the air. A small bag of desiccant is also added to help with damp.


Conclusion


So, there you have it, a guide to PETG and all its properties both good and bad. As an alternative to PLA it's definitely worth a go especially if you’re wanting to print hard wearing and weather resistant items. The settings on your printer may take some time to perfect and there’s definitely a bit more wear and tear on the nozzle etc. but all in all PETG filament is a good choice for any 3D printing enthusiast.






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