Their original purpose was something entirely different whereas PETG is that category of thermoplastics which is specially developed for 3D printing.
Its key features have subtle differences as compared to its counterparts, but they make all the difference. It produces little to no odor during printing and has real strength combined with enhanced flexibility and durability.
It has better layer adhesion for improved surface finish and has a higher melting point than PLA.
It is ideal for building mechanical parts and has more flexibility than ABS, PLA and even PET. The general temperature range for this thermoplastic is 220-235C. It does not require a heating bed, and there is minor shrinkage after cooling. It is eco-safe and can be properly recycled. It rarely warps and is known for its clarity and bridging properties.