If you went out and bought a bottle of water right now, there is a high chance the bottle would be made from PET plastic. 30 percent of the world’s plastic bottles are made from PET.
It is the most commonly used plastic, finding its way into everything from clothing to the clamshell packaging fast food restaurants use.
Polyethylene terephthalate glycol or PETG is a thermoplastic polyester derived from PET. Thanks to the glycol added to PET, PETG is stronger, lasts longer and is more heat and impact resistant. These characteristics make it a ready alternative to other 3D printing filaments when printing items used outdoors.
PETG can however, be a little complicated to print with. This is why it is not as popular as either ABS or PLA. But what specific material advantages does PETG offer and how does it perform when exposed to water or heat from the sun?
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Is PETG Filament Waterproof?
Depending on its application, waterproofing can be an essential feature of a 3D printed item. Plastic that needs to be used in wet environments like swimming pools or cisterns should be able to function without breaking down. PETG is one of several filaments that can be used to print waterproof items.
Most plastic is waterproof. This is actually one of the reasons why plastic is considered a big environmental problem. It takes plastic up to 450 years to decompose in water. With that said, plastic becomes weaker as it is exposed or submerged in water for long periods.
With some plastics, the degradation is increased or slowed down by the temperature of the moisture. PLA, for example, breaks down quicker when exposed to hot rather than cold water.
Like most printing materials, PETG can also be coated to improve its weather resistance. Powder coating and clear acrylic sealant are popular options for giving outdoor PETG prints an extra layer of protection. Source
Will PETG Melt In The Sun?
The ultraviolet (UV) resistance of a material gives an indication of how it will react to the sun. Sunlight gives off UV radiation which breaks down plastic material. One of the characteristic qualities of PETG is its high UV resistance. PETG has a heat deflection temperature of 70 degrees Celsius and a glass transition of 85 degrees Celsius.
Heat deflection and glass transition temperature are two of three measures of a material’s reaction to heat. Fused deposition modeling (FDM) 3D printers apply heat to filament to melt it and extrude it to produce a print. This is the melting or printing temperature of a filament.
The glass transition temperature (Tg) on the other hand is the temperature at which a 3D print goes from hard to soft due to exposure to heat. The glass transition of a material is important because it determines how well a print will perform under heat.
It’s a major consideration when choosing a material that will be used to print anything that will be used outdoors or anywhere subject to extreme heat. Materials used in the automotive and aerospace industries for example, need to have a high glass transition as they experience intense heat.
| FILAMENT | PRINTING TEMPERATURE (°C) | GLASS TRANSITION TEMPERATURE (°C) |
| PETG | 220 – 250 | 85 |
| PLA | 180 – 230 | 55 – 60 |
| ABS | 210 – 250 | 105 |
While ABS has a higher glass transition, PETG has shown to be more robust when exposed to the sun’s UV radiation. It typically lasts longer than ABS which tends to weaken under UV radiation.
For more on this, check out our post on ” Does ABS Warp In The Sun? Can It Be Used Outdoors !“