PeT (Polyethylene Terephthalate)
is a strong but lightweight form of clear polyester. It is used to make containers for soft drinks, juices, alcoholic drinks, water, edible oils, household cleaners and other food and non-food applications. Being a polymer, polyethylene terephthalate’s molecules consist of long chains of repeating units only containing the carbon (C), oxygen (O) and hydrogen (H) organic elements.
PET was first developed for use in synthetic fibers by British Calico Printers in 1941. The patent rights were then sold to DuPont and ICI who in turn sold regional rights to many other companies*.
PET began to be used for packaging films in the mid 1960s and then, in the early 1970s, the technique for blowing bi-axially oriented bottles was commercially developed.
Bottles now represent the most significant use of PET moulding resins. Making a PET bottle starts from the raw material: ethylene and paraxylene. These two substances’ derivatives (ethylene glycol and terephthalic acid) are made to react in order to obtain the PET resin. The resin, in the shape of small cylinders called pellets, is melted and injected into a mould to make a preform. The preform – a sort of test tube, shorter than the final bottle but with thicker walls – is then blow-moulded. During the blow-moulding phase, high-pressure air is blown into the preform allowing it to take the exact shape of the mould it is set into. The final product is, thanks to the molecular structure of the material, a transparent, unbreakable, resealable and lightweight bottle.