PETG vs. PLA: Differences and Comparison
Learn more about the differences between these two materials and the advantages and uses of each.
PETG is a glycol-modified variant of polyethylene terephthalate. PLA, poly(lactic acid) or polylactide, on the other hand, is a thermoplastic derived from lactic acid. Both materials are classed as polyesters. The main differences between the two are their properties, applications, and material costs. PETG is stronger and more resilient than PLA. PLA, on the other hand, is widely used as FDM/FFF filaments because of its better melt and cooling properties. In terms of cost, PETG is more expensive than PLA.
This article will discuss the differences between PETG vs. PLA, their advantages and disadvantages, as well as their alternative materials.
PET or polyester (DuPont Dacron) was first discovered in 1931. It was commercialized as Terylene, stretched sheet material, and for blow-molded bottles in the succeeding years. PETG is manufactured from crude oil-derived materials. The addition of the glycol group (PETG – PETGlycol) improves the thermal properties by making a less uniform polymer chain. This addition results in a lower melting point and lowers residual stress from cooling. Despite poorer cosmetic qualities, PETG is often preferred over PLA because of its greater resistance to creep, and resistance to scratching.
PETG has these advantages over PLA:
- PETG is more elastic, making it better at resisting shock loading.
- PETG is more chemically stable than PLA.
- PETG has higher impact strength than PLA, reducing the risk of fracture.
- PETG has higher hardness than PLA, making it more able to resist abrasion.
The following are the disadvantages of PETG vs. PLA:
- PETG is harder to hand finish than PLA.
- PETG requires higher processing temperatures than PLA
PLA was first discovered in the 1930s at the same DuPont lab as PET/Dacron. But it was not commercialized until the 1980s by Cargill Inc. PLA is a polymer that is essentially a polyester, related to PET. The lactic acid source material can be derived from a number of natural and renewable sources such as corn starch and sugar cane. PLA was specifically commercialized as a “green” substitute for PET. This is due to PLA being made from renewable materials and having the characteristic of degrading quickly. PLA also makes an excellent filament for FDM as it has very low viscosity at the nozzle and cools to a hard and resilient finish.
The advantages of PLA vs. PETG are:
- PLA produces higher cosmetic quality parts than PETG when processed using FDM.
- PLA is more environmentally friendly than PETG.
- PLA requires a lower temperature to melt, making it compatible with a wider range of machines.
- PLA is more amenable to hand finishing than PETG.
Below are the disadvantages of PLA vs. PETG:
- PLA is weaker and more prone to fracture than PETG.
- Inter-layer bonding of PLA is poorer. PLA parts are more anisotropic than those made from PETG.
- PLA is more prone to stringing than PETG. This requires tuning in some printer settings.
- PLA parts are susceptible to moisture and UV and are less temperature stable than those made from PETG.
Greater intra-slice bonding and material strength (tensile strength)
Yes at 53.08 MPa
No at 49.98 MPa
More elastic and has a higher yield strength
Yes at 238 J/m
No at 152 J/m
High print cosmetic quality
Has more tendency to leak during non-printing movements, leaving strands (stringing)
$20–25 per kg
$15–20 per kg
Usable on more and lower-cost machines
Makes models that are more easily sanded
Table 1: PETG vs. PLA Comparison
Model strength and resilience are considerably higher for PETG. The cosmetic quality of model surfaces, however, is generally better for PLA.
PETG is better for strength, wear resistance, and chemical resistance. Stressed components and moving parts are better when made in PETG. Model parts in motion and contact against other components will be more resilient in PETG. Parts that will experience either water, sunlight, or heat exposure will also be better in PETG. PLA is better suited to low-stress, cosmetic applications, and components that require a better finish quality.
PLA is better suited to maintaining part precision. This is because of its better printability and lower warping. It should be noted, however, that under steady load, PLA tends to creep. For smaller features, PETG bonds better, as it is more viscous in the melt state and achieves better intra-layer coupling.
PETG is more sensitive to print speed than PLA. Newly extruded material may not stick to the layer below or the last strands if the print speed is high. PLA is more sticky, due to its lower viscosity. This results in PETG model build speeds being lower than those of PLA.
Both materials produce similar surface finish quality. Although in many cases, PLA models appear smoother because of the lower melt viscosity.
PETG has a considerably higher melting point than PLA (180 °C for PETG, 165 °C for PLA).
PETG is derived from crude oil and is environmentally stable. Its life in landfills is measured in centuries. It does experience some degree of UV degradation, shortening the breakdown. PLA is a fragile polymer, and its environmental resistance is so short that it can influence the shelf life of the packaged product.
PETG and PLA meet the GRAS (Generally Recognized As Safe) standard and are food safe. Two considerations may influence the application of FDM/FFF parts in food safety terms:
- Depolymerization occurs when plastics are overheated, producing non-food-safe results. This is more likely to occur in the case of PLA, as the polymer chains are more prone to scorching during extrusion.
- Coloring agents used in the polymers are likely to NOT be food-safe – and PLA may allow these dye agents to leak.
These factors do NOT imply that printed parts are not food safe. But care should be taken to minimize the use of FDM and FFF parts in food contact.
PETG has a typical cost range of $20 to $25 per kg. This depends on the material class, supplier, and volume purchased. Standard PLA, on the other hand, costs around $15 to $20 per kg.
Below are the mutual alternatives to both PETG and PLA:
- ABS: Acrylonitrile butadiene styrene (ABS) is a popular alternative to both PETG and PLA. It can produce good quality, high-strength models. Although, there's a risk of warping and strong smell, requiring tight control of settings. ABS is also much harder to use than either PETG or PLA.
- ASA: Acrylonitrile styrene acrylate (ASA) is related to ABS, except that it has greater UV resistance, making it ideal for outdoor uses. ASA suffers the same setup and printing issues as ABS and they are both considered good alternatives to both PETG and PLA.
- PC: Polycarbonate (PC) is also an alternative to PETG and PLA. It has high clarity but requires high-temperature extrusion, limiting its application.
PETG and PLA do have significant similarities, which are :
- Their extrusion temperatures are within 15°C of each other, making them interchangeable on most machines.
- They can both be transparent or colored.
- They are the low-cost materials of choice for the majority of FDM/FFF modeling.
One not very commonly available material directly compares with PETG:
- PETG vs PCTG: PCTG (Polycyclohexylenedimethylene terephthalate) is considered a good alternative to PETG. It offers higher bonds, tensile strength, and clarity. PCTG, however, has a 250–270 °C nozzle temperature, which is out of reach for some printers. Interestingly, PCTG is able to print matte or gloss depending on extruder temperature.
The material that most closely compares with PLA is enhanced PLA (or PLA+):
- PLA vs. PLA+: PLA+ is a family of easy-to-print materials with enhanced properties compared to PLA. It is made from PLA with a range of additives. Examples of additives are:
- Calcium carbonate to improve tensile strength
- Carbon fibers to enhance flexural strength
- Metal flakes to make metallic-looking prints
- Nucleating agents to enhance layer bonding
This is a wide family of materials – whose costs reflect the complexity of manufacture and enhanced performance.
This article compared PETG vs. PLA as a material for use in 3D printing applications. To learn more about the differences and similarities between PETG vs. PLA and how these can be applied to your products, contact a Xometry Representative for guidance and expert advice.
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