Polyester (PET)

Semi-crystalline thermoplastic

Polyester is a category of polymers that contain the ester functional group in their main chain. Although there are many types of polyester, use of the term "polyester" as a specific material most commonly refers to polyethylene terephthalate (PET). Depending on the chemical structure, polyester can be a thermoplastic or thermoset; however, the most common polyesters are thermoplastics.