Polythene terephthalate (PET) is an inexpensive thermoplastic resin manufactured in both an amorphous and semicrystalline form. The amorphous form of PET is transparent and ductile -- meaning that it can undergo stress and deformation without breaking -- while the semicrystalline form is hard and relatively inflexible, and ranges in colour from clear to opaque.

PET provides a strong gas and moisture barrier, making it a popular choice for plastic bottles for drinks, sauces and salad dressings; microwaveable food trays; and food packaging. Bottles made with PET will not shatter, and weigh about a tenth as much as their glass counterparts, which makes them ideal for beverages and personal care products. Polyester fibres made of PET comprise everything from bed sheets and pillow stuffing to draperies and tire cord. Polyester also blends easily with natural fibres in fabrics, and resists wrinkling.

Extensive testing of PET has established that a minimal amount of substance transfer occurs between PET packaging and food. Therefore, it does not pose a risk to human health. Additionally, a study conducted by the International Life Sciences Institute indicates that PET and its associated compounds are "biologically inert if ingested."

According to the National Association for Plastic Container Recovery, the average household generated 19.1 Kilogram of PET bottles in 2005. Fortunately, PET is easy to reprocess, and readily breaks down into its basic monomers. Recycled PET is a common ingredient of bottles, packaging, carpet fibre, hats, luggage, insulation, furniture and health care product containers.

A 2010 study by scientists at the University of Pittsburgh examined the environmental consequences of biopolymer production, and ranked PET last in terms of negative impact, based on such factors as biodegradability, per cent recycled, mass from renewable sources, life cycle health hazards and life cycle energy use. (Polypropylene ranked first, followed by high- and low-density polythene polymers and polyhydroxyalkanoate.)