PETG, CPE and CPE+ are all part of the co-polyester family. However, they differ both chemically and in the properties of their respective printed parts.
PETG is a glycol modified polyethylene terephthalate. CPE is a branched version of this, while the specific polymer in CPE+ is a PCTG (polycyclohexylenedimethylene terephthalate glycol-modified).
With respect to their printability, Ultimaker PETG is the easiest to print and to achieve good visual quality, such as good bridging and overhangs, especially when using the visual (default) intent profiles in Ultimaker Cura. PETG also has the widest availability of colors, including translucent and fluorescent options, enabling a wider variety of visual applications. On the other hand, CPE+ is the most difficult to print material of the co-polyesters, which is most obvious in large or thin walled models.
If we look at the mechanical properties, Ultimaker PETG has the best all-round properties and superior stiffness. CPE+ has the best wear resistance and toughness of the co-polyester materials. CPE will provide a good stiffness and wear resistance, but a lower toughness.
All co-polyester materials have good chemical resistance against alcohols (EtOH, IPA), water, acids and bases. With longer duration or higher concentration of the chemical, CPE+ followed by CPE will provide a higher resistance before being affected. More information about chemical resistance can be found in this article.
CPE+ has the highest temperature resistance amongst these co-polyesters and is suitable for applications where the printed part is exposed up to 100°C. CPE and PETG have quite similar temperature resistance, where CPE can be used up to 78°C and PETG up to 76°C.
I am now using CPE, can I use PETG instead?
Unless you require the specific chemical resistance of CPE, it is very likely that you would prefer to use PETG instead. You will benefit from improved printability, while retaining or exceeding the mechanical properties of the printed part.
All specific data can be found in the technical data sheets of the respective materials. The differences are summarized in the overview below.