PETG Filament for 3D Printing
PETG filament belongs to the PET family of thermoplastics used for 3D printing. Do you wonder if this is the same PET symbol that we see on plastic bottles or sailcloths? Well, you are partially correct because PETG is a variation in PET(Polyethylene Terephthalate) thermoplastics enriched with glycol during polymerization. The glycol content keeps the plastic from crystallizing and makes it a bit softer. This also reduces the melting point of the thermoplastic.
Melting Point
PET - 260°C
PETG - 230°C
The PETG filament has an outstanding adhesion between layers which results in great improvement of the impact resistance, strength, and durability. “It’s an excellent filament choice for printing objects that need to be sturdy, have a smooth surface, and require lower shrinkage.”
Formation of PETG
PETG is formed by the copolymerization of PET thermoplastic. During this process cyclohexane dimethanol (CHDM) is added to the composition instead of ethylene glycol. Thus, resulting in a block of longer atoms, where the adjacent chains do not fit as the ethylene glycol. With this, crystallization can be stopped when an effort is applied to this material. Due to the ease of extrusion and thermal stability, PETG is a good choice for a filament.
When to use PETG filament?
If you want your 3D printed structure to be physically stronger and durable, PETG is the correct option for you. It has an excellent temperature tolerating capacity that makes it favorable for high temperature and outdoor 3D printing applications. Transparency is easier to achieve with PETG filaments due to their layer fusing capacity. PETG filament is highly chemical resistant, so the 3D printed models are difficult to dissolve using acidic substances.
There are different blends of PETG filaments with different properties. For more information visit this article.
Is PETG filament ideal?
PETG filament is not ideal for all 3D printing applications, it has some drawbacks. It is a less dense material because of its high impact resistance and bendable property. This feature makes it easily scratchable than acrylic sheets and glass. PETG filament is not ideally suitable for aesthetic applications and is comparatively expensive than the PLA filament. PETG filament cannot be vapor smoothed like the ABS filament. However, it can survive more intense post-processing than PLA.
When the temperature in the print head is too high then the filament becomes viscous and leaks out of the print nozzle. This causes the formation of strings when the nozzle moves between two points during the printing process. Hence, PETG is “notorious for stringing as it requires a relatively higher temperature to ensure good flow.” There are many ways to prevent stringing, these can be found in this article.