Polyester is a category of polymers that contain the ester funcitonal Group in their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). [1]
Polyesters important in conservation
Polylactic acid (PLA)
Poly(lactic acid) or polylactic acid or polylactide (PLA) is a biodegradable and bioactive thermoplastic aliphatic polyester derived from renewable resources, such as corn starch (in the United States and Canada), cassava roots, chips or starch (mostly in Asia), or sugarcane (in the rest of the world). [2]
This polyester might right now not be used in conservation but maybe in its environment as it is used for 2d printing and injection molding. It is decomposable. A film made of PLA shrinks upon heating.
References
Photograph: Polyester Cloth from Wiki Commons, Attribution: Damieng at the English language Wikipedia
[1] Wikipedia Polyester
[2] Wikipedia Polylactic acid