PET is a polyester polymer that is used in plastic packaging and molded products. It is a clear and transparent plastic that is lightweight, strong and has excellent mechanical properties. It can be shaped into bottles, jars and other containers and is virtually shatterproof.
It can be recycled many times over and is one of the most commonly used polymers for consumer packaged goods. The polymer is made from the polymerization of terephthalic acid and ethylene glycol. The two are heated in a low vacuum pressure to form molten PET.
The polymer can be modified in several ways to improve performance. For example, cyclohexanedimethanol can be added to the polymer backbone in place of ethylene glycol. This creates a kink in the polymer chain that interferes with crystallization and lowers the melting temperature.
Another common modification is isophthalic acid, which replaces some of the 1,4-linked terephthalate units. This produces a 1,2-(ortho) or 1,3-(meta-) linked terephthalate unit that creates an angle in the polymer chain. This lowers the melting point and also helps to improve strength and stiffness of the polymer.
PET is an essential component of the circular economy and is widely used to package beverages, food and other consumer products. Almost 60% of the waste we produce can be recycled and PET is a good choice for this purpose.