What is PET And The Science Behind PET


What is PET?

PET is short for polyethylene terephthalate – it’s a chemical name for polyester. PET is manufactured by transesterification reaction by combining ethylene glycol and terephthalic acid under low vacuum pressure and high temperature to form a polymer chain. It is a thermoplastic polymer resin of the polyester family.

This polymer is extremely stable, tough and inert as well. PET is highly resistant to most of the chemical or biological reaction with other substances and this is the main characteristic of the PET which makes it safe to use in almost all the applications. PET has varied applications and it’s not only used for convenience-sized and water bottles but also for packaging foods and beverages. The names and acronyms for many of these plastics are similar, but they have different properties and chemical structures.

PET-Preform, PET-Rohling, PETling
PET-Preform, PET-Rohling, PETling (Photo credit: Wikipedia)

Dispelling Myths and Misconceptions About PET

There are many misconceptions about PET which has led to nonsensical rumours and erroneous assumptions. First of all PET does not contain BPA. BPA is short for Bisphenol A which is a compound to manufacture Polycarbonate. PET does not contain BPA and never has.

PET contains no Phthalates (i.e., phthalate ester plasticizers or orthophthalates) are not used in PET, nor is PET a phthalate. Plasticizer phthalates are sometimes used to soften other types of plastic, and are believed by some to be potential endocrine disruptors although this is unproven. The confusion seems to come from PET’s chemical name, polyethylene terephthalate. Despite the suffix, PET is not a plasticizer phthalate. Phthalates are low molecular weight monoesters made from ortho-phthalic acid. PET is high molecular weight polyester made from tere-phthalic acid. They are completely different chemicals.

About Aldehydes

In PET Bottles trace amounts of acetaldehyde, and to lesser extent other aldehydes are unavoidable which are by-products of it. In the Modern manufacturing processes of the PET industry are using various methods to minimize the formation of aldehydes.

Acetaldehyde is a naturally occurring substance found in many foods, especially ripe fruits, including apples, grapes and citrus fruits. It is also a natural constituent of butter, olives, frozen vegetables and cheese, and is formed in the body when certain foods are digested.

The insignificant amounts of aldehydes that may be found in PET or PET-packaged items are far lower than the typical levels found in many of these foods or in the human body, and pose no health risk.The main concern over trace amounts of acetaldehyde in PET-bottled beverages is literally one of taste. Very few individuals with very highly developed olfactory senses can sometimes detect its faintly fruity taste in bottled water.