3D printing with PLA vs. PETG: What's the difference?

PLA and PETG are two popular materials for FDM 3D printing. In this article, we’ll compare the two, so you can choose the best material to use for your 3D-printed custom parts.

What is PLA?

PLA (polylactic acid) is a thermoplastic that is commonly used in 3D printing. It is made from the fermented sugars of plant-derived materials, such as corn starch or sugar cane. It is also recyclable and can be composted by industrial composting facilities.

The properties of PLA include the following.

• High stiffness. PLA is stiff and brittle when compared to materials such as ABS or PETG. This means it is not always suited to parts that require high degrees of flexibility.

• Good strength. PLA is a relatively strong material, featuring a flexural strength of 103 MPa.

• Low melting point. A melting point of approximately 175°C makes PLA well-suited for 3D printing.

• Easy to print. Additionally, PLA can be printed at a range of temperatures past its melting point with good flow and end results. This makes PLA easy to print with. 

• Fine details. PLA material can be used to create parts that exhibit fine details, as it cools quickly and holds its shape well, even when past its melting point. This makes features such as sharp corners and overhangs print well. However, a minimum feature size of 1.2 mm is recommended.

• Low UV and temperature resistance. PLA will quickly deform when subjected to heat – even at temperatures as low as 50 °C – and UV light.

• Chemical resistance. PLA is fairly chemical-resistant and is not soluble in certain solvents (such as isopropyl alcohol). However, certain chemicals can cause it to release lactic acid, which can be harmful in large quantities.

• Susceptibility to creep. PLA is known to permanently deform when under constant loads over a long period of time, making it less suitable for applications such as spring clips or snap fits. 

What is PETG?

PETG (polyethylene terephthalate glycol) is a thermoplastic that offers improved mechanical properties over PLA. This is why it is often used in industrial applications. It is not biodegradable, but it is recyclable.

The properties of PETG include the following.

• High impact resistance. PETG’s high impact resistance means it is well suited to applications in which durability and toughness are needed.

• Higher flexibility. PETG is more flexible than PLA, meaning any application that requires the property, such as spring clips or plastic snap fits, are better-suited to PETG.

• Excellent chemical resistance. PETG exhibits high degrees of chemical resistance, meaning it’s a good choice if your parts will be exposed to solvents, oils, or chemicals.

• Excellent moisture resistance. Because it does not retain moisture, PETG is often used in outdoor applications. 

• Food-safe. PETG is non-toxic and food-safe, meaning it is a great fit for food and beverage industry applications.

• Good formability. PETG is ductile, and can be more easily formed into complex shapes than PLA.

What’s the difference between PLA and PETG? 

We’ll explore the main differences between PLA and PETG in the below sections. Generally, however, PLA is more suited to prototyping and applications in which durability is not essential, while PETG is a better choice for industrial applications that require toughness and functionality.

What are the advantages of PLA vs. PETG? 

Sometimes, you might not need the improved mechanical properties of PETG. In these cases, PLA is a great choice, and provides the following advantages.

• Cost considerations. PLA is usually cheaper than PETG.

• Simplicity and printability. PLA adheres well to build surfaces, has minimal warping, and generally requires less fine-tuning of printing settings. This makes PLA a preferred choice for beginners or those who prioritize hassle-free printing.

• Wide availability. Standard PLA is widely available and comes in a variety of colors and formulations. This availability can be advantageous for users who need a specific color or property readily accessible.

• Non-functional prototypes. PLA is a great material for quickly prototyping part geometry, especially when you don’t need to test the prototype’s strength or material properties.

• Better UV resistance. Compared to PLA, PETG is a bit more resistant to UV degradation, although it can still degrade over time (years).

• Better temperature resistance. PETG resists warping in moderate to high temperatures better than PLA. It starts warping around 80 °C rather than 50 °C for PLA.

What are the advantages of PETG vs. PLA?

Most of PETG’s advantages over PLA are found in its mechanical properties, which enable the material to perform better under rigorous conditions that are often found in industrial environments. Let’s take a look at a few applications in which PETG would be a preferable material over PLA.

• Functional prototypes. Whereas PLA is useful for non-functional (or visual) prototypes, you can use PETG to create a prototype with material properties that closely resemble a final product 

• Industrial components. PETG’s high impact resistance and resistance to chemicals and moisture means it often finds a place in various industrial components subjected to hardworking conditions.

• Tough consumer products. Its impact-resistance and durability make PETG a solid choice for creating consumer-focused products such as phone cases or housings for electronics.It is also often used for automotive applications, as well as other indoor-outdoor products. 

• Higher heat resistance. PETG has a higher glass transition temperature than PLA, making it a better choice for applications that are exposed to heat.

What are the disadvantages of PETG?

PETG is more prone to scratching than PLA. It is also trickier to print, as it requires higher printing temperatures, and has a tendency to stick to the print bed. It is also more prone to oozing. Additionally, it may be more difficult to remove supports (if used), because PETG tends to be a bit harder to separatethan PLA.

Surface finishes and post-processing for PLA

There are several post-processing techniques that can further enhance the appearance of PLA parts. Here are a few of the surface finishes and post-processing methods for PLA that our customers commonly use.

• Sanding. You can sand PLA parts to smooth out layer lines and imperfections on surfaces.

• Priming and painting. Applying a primer to PLA parts can create a smoother surface, and painting allows for customization with various colors and finishes.

• Epoxy coating. You can apply a thin layer of epoxy resin can provide a glossy and protective finish to PLA prints.

• Polishing. You can polish PLA parts using a buffer to create the smoothest possible surfaces.

• Vapor smoothing. When using the proper solvents and materials, PLA can be vapor smoothed, but this process is best handled by professionals with experience handling chemicals. (If you want to vapor smooth PLA, consider using an outside service such as Protolabs Network to produce your FDM parts.)

 

Surface finishes and post-processing for PETG

PETG is compatible with the post-processing techniques listed above. You can also use methods such as vapor smoothing, torch polishing, or vapor bathing – all of which are more difficult to achieve with PLA, and may cause it to deform.

Get custom PLA and PETG parts  

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For more information, learn about choosing the right materials for your application and our comprehensive guide to plastics.