PETG vs PLA Filament

Today we will be looking at the differences between two common 3D printer materials, PETG and PLA. Though at first glance these materials may seem similar, they are in fact surprisingly different. Let’s talk about it!

PLA:

So firstly let’s take a look at PLA. PLA stands for PolyLactic Acid and is a naturally derived plastic made from cornstarch. This differs from most materials which are oil based which leads to this material being more environmentally friendly.

One major benefit of PLA as a material is that it is Biodegradable, other oil based plastics can take over 400 years to biodegrade also leave behind toxins in the ground, in the right conditions PLA only takes 60 and leaves no toxins behind.

So you may be asking, is it a good material to print with? Well generally yes. PLA is now the most common material people print with. The main reason for this is that is is really easy to print with. When printing other plastics such as ABS, the plastic warps massively when cooled, this is not an issue with PLA and it can even be printed with no heated bed. Due to this almost every FDM Printer can print this material which is why it is so widely used. As the material is so easy to print, it can often be printed faster than other types of materials.

PLA also has other benefits such as it having little to no smell when being printed, the only smell released is a sweet scent. The material also offers a resistance to the environment around it, the filament does not soak up moisture and can be left open for large amounts of time however, it is recommended to keep it sealed in a bag.One other benefit to PLA is its high hardness, a feature that is useful when you want no flex in your prints.
Finally PLA just looks good. Prints come out crisp and well formed which is a massive pro for anyone looking to make beautiful models without any artefacts.
There is also a wider range of filaments in PLA such as Flame retardant filament or Conductive filament.
So let’s get onto some of the downsides to this magical material! We know that PLA is very hard but unfortunately it is also very brittle. This causes prints under strain to snap relatively easily.

Another common problem with PLA is the temperature resistance. Prints that are made from PLA will deform if left in the heat. I have personally had this happen when leaving a print in direct sunlight on a hot summers day.

Apart from that there really are no other downsides to PLA as a filament.

PETG

So now let’s move onto PETG! PETG stands for PolyEthylene Terephthalate Glycol, quite a mouthful but let’s digest it. You may be used to seeing a very similar material to this called PET. This is used in water bottles and other recyclable single use plastics. PETG is very similar to this but with the addition of the Glycol. Glycol is added to the material to make it printable, without it the filament would be cloudy and weak.

Pros:

So what are the pros of PETG, Well thanks to the added glycol, this material is a reasonably durable. This material is capable of withstanding quite a bit of damage due to the added flexibility. Though not too flexible this material does have a bit of give. Along with the extra durability these materials are also are quite scratch resistant. This would be perfect if you are using it a situation where your part is being used in a rough situation and you do not want damage to show.
Another great feature when using PETG is its heat resistance. The glass transition temperature (the temperature where a material softens) is around 80 degrees Celsius. This is an enormous benefit if you are planning to store your printed part somewhere warm like a car or an attic. And that is about it for the positives for PETG.

Cons:

Now let’s get onto some of the cons about the material. Unfortunately there are quite a few but all of these issues I am about to explain are not major, just slightly irritating.

Firstly PETG is hygroscopic – a fancy word for it being absorbent. This means that it can easily get damaged in damp situations. This causes the materials to pop when the water goes through the hotend and leaves prints with an unwanted texture. Luckily this is easy to prevent and fix.  To dry your filament just stick your filament in the oven at 60 degrees Celsius for 4 hours. To store you Filament correctly it is always good practice to keep it in a sealable bag.

Another issue with PETG is stringing. Stringing is when small residues parts of plastic are left on your prints. These look like little hairs. This is also not a massive issue as it is entirely possible to remove them with heat and some snippers. Unfortunately this does effect the quality of the print though. Surfaces are also not usually very good looking, this is due the PETG naturally being very translucent. This sometimes makes prints appear to have scars from the light being reflected on the print.

Finally, the last issue I would like to talk about is post processing with this material. Unfortunately PETG is a very slippery filament, this means that it is very hard to post process. When painting PETG, the paint will not stick very well to the material. As we talked about earlier, PETG does not scratch very easily, this is also a negative when you would like to sand your prints. Lastly, many glues and epoxy resins will not adhere to this materials which makes it hard to stick parts together. The only way that I have managed to get parts to stick is by friction welding them, this used heat to merge two parts together to form one.

So let’s summarise what we have looked at today! Firstly let’s talk about heat resistance, when you want to print something that needs to be able to withstand heat, I recommend that you use PETG. If you are looking to print some awesome models and you need detail, accuracy and the ability to be post processed I recommend that you use PLA as it can take paint and glue well and the surface finish is generally much better than PETG.

If you want a material that is just easy to use I recommend you use PLA, you don’t really need to store it in a special way and it prints at relatively low temperatures and has little to no stringing. If you are looking to print some tough models that need to take a bit of wear and tear I recommend that you use PETG due to its slight flexibility and scratch resistance. If you are concerned about the waste of 3D printing, don’t be! Both of these materials will not harm the environment if disposed of safely.

So to conclude, it really depends on what you print. I generally use PLA more than PETG just because it is easy to print and it doesn’t require me to do any cleanup after the print is done. My prints don’t normally get beaten around or over heated so for my prints I use PLA.

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