Polyethylene terephthalate (PET) is a thermoplastic polymer resin and a member of the polyester family. It is the material used for most single-use beverage bottles and many other containers found on store shelves. PET’s prevalence is due to a unique combination of physical properties that make it an economical, lightweight, and efficient packaging choice. The material is designated by the Resin Identification Code “1” and is a primary focus of plastic recycling efforts worldwide.
Understanding the Material Polyethylene Terephthalate
PET is synthesized through a chemical reaction called polymerization, which combines two monomer building blocks: purified terephthalic acid and ethylene glycol. This process links these molecules into long, repeating chains that give the final plastic its strength and stability. The resulting chemical structure is a linear polymer with repeating ester groups.
The material’s physical characteristics make it ideal for bottling liquids. PET is exceptionally lightweight, which significantly reduces shipping weight and transportation costs. It possesses high mechanical strength and is shatter-resistant, making it a safer alternative to glass for consumer products.
Crucially for the beverage industry, PET provides an excellent barrier against gases like oxygen and carbon dioxide. This gas barrier property allows carbonated drinks to retain their fizz over time and protects sensitive contents from degradation due to atmospheric oxygen. Depending on how the polymer is processed, it can be manufactured to be either amorphous and glass-clear or semi-crystalline for enhanced strength and rigidity.
Widespread Use Beyond Beverages
While PET is best known for beverage bottles, its properties lend themselves to a wide array of other applications. It is routinely molded into rigid food containers for products like peanut butter, cooking oils, and salad dressings. Its clarity and durability also make it a popular choice for packaging cosmetics and personal care items, such as mouthwash and shampoo.
The material’s use extends far beyond containers into the textile industry, where it is known as polyester. Polyester fibers are woven into various fabrics for clothing and are used as fiberfill for pillows, furniture, and sleeping bags. A stretched, thin form of PET is also manufactured into durable films, which have applications in everything from packaging films to magnetic recording tape.
Safety, Health, and Reusability
Safety evaluations by regulatory bodies worldwide, including the U.S. Food and Drug Administration (FDA), have deemed PET safe for food and beverage contact. The polymer is free of Bisphenol A (BPA). BPA is an ingredient associated with other types of plastic.
Public concern regarding chemical leaching from PET bottles often stems from a misunderstanding of the material’s composition. Trace amounts of acetaldehyde, a residual byproduct from manufacturing, can sometimes migrate into the contents, but these levels are below safety thresholds. Repeated use of a PET bottle is discouraged, not due to chemical leaching, but because physical degradation, such as scratches and cracks, can harbor bacteria. This mechanical wear makes proper cleaning difficult, increasing the risk of microbial contamination.
The Recycling Process and Environmental Status
PET is one of the most widely recycled plastics and is easily identifiable by its Resin Identification Code #1. The mechanical recycling process begins with the collection and sorting of used bottles, separating them from other plastics and contaminants. The sorted bottles are then washed to remove labels, caps, and adhesive residue.
Next, the cleaned bottles are shredded into small fragments called flakes. These flakes are subjected to decontamination, often involving heat and vacuum, to ensure the resulting material is safe for new food-contact applications. The purified flakes are then melted and pelletized into a material known as recycled PET, or rPET.
This rPET can be incorporated into the production of new beverage bottles, creating a closed-loop system known as bottle-to-bottle recycling. It is also a primary source material for manufacturing new polyester fibers, which are used to make items like carpet and clothing. The lightweight nature of PET contributes to a lower carbon footprint during transportation compared to heavier packaging materials like glass, making it a preferred material for achieving circular economy goals.