PET is converted into PETG, which stands for "polyethylene terephthalate-modified" because some of the ethylene glycols are substituted with CHDM (cyclohexanedimethanol), a substance you may be familiar with from plastic water bottles. The end product is a filament PETG that is clearer, less fragile, and more extrudable than PET. It does, however, have the unfortunate side effect of altering the recycling process. PETG is not commonly recycled, even though PET is; the minute variations in these materials lead to a problematic contaminant in recycling operations.
