PET vs PETG: The Main differences: PET and PETG – this family of polymers is practically everywhere in our lives. While it’s not surprising that water bottles, food containers, and soap dispensers are made from this material, automotive parts, electrical devices, and textiles also rely on PETs.
All this popularity, undoubtedly linked to low cost and great properties, has also attracted the attention of 3D printing creators and enthusiasts. PETG is often the first choice for medium-range temperatures and mechanical strength on a low budget, as it is cheap, easily available, and easy to print.
The basic formula for producing polyesters such as PET and PETG is a combination of acid and glycol monomers. In the case of PET, the acid is usually DMT (dimethyl terephthalate), and the glycol is ethylene glycol. These two monomers are building blocks for the final long-chain polymer: polyethylene terephthalate.
In the case of PETG, the same monomers are used, but a certain amount of ethylene glycol (30-60% according to the literature) is replaced with another glycol monomer, CHDM (cyclohexane dimethanol). So it’s not that PETG has significantly more or less glycol than PET, it simply has a different type of glycol. Therefore, the -G in PETG stands for the chemical modification of the typical PET structure with CHDM glycol units, or simply “glycol-modified”.
PET and PETG – what are they and what are the differences?
PET (polyethylene terephthalate) is a plastic material that is a popular choice for 3D printing. It is impact-resistant and perfect for printing high-detail parts. PET is also very easy to print and its cost is affordable.
PETG (glycol-modified polyethylene terephthalate) is a material with similar properties to PET, but with the addition of glycol, which improves its impact resistance. PETG is also more flexible and scratch-resistant than PET. However, its price is slightly higher than that of PET.
Semi-crystalline materials are usually stiffer compared to completely amorphous counterparts, as the crystalline areas can act as reinforcement. This applies to semi-crystalline PET and amorphous PETG. Although the mechanical properties of these two polymers are usually very similar, PETG can be stretched slightly more.
Which material to choose?
If you’re looking for a material for printing parts that require high detail, PET is a good choice. It is also cheaper than PETG, which means it can be used for printing larger projects. On the other hand, if you need a material that is more impact-resistant and scratch-resistant, as well as more flexible, PETG is a better choice.
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