PET or polyethylene terephthalate

This article on PET manufacturing describes the polycondensation processes used in the world's major industrial plants. The two main routes to this polymer are distinguished by the chemical form of one of the two monomers, terephthalic acid (the other being ethylene glycol), at the start of this synthesis.

Terephthalic acid can be in the form of a methyl ester, dimethyl terephthalate (DMT), or as is, in purified acid form (PTA). Today, the new plants operate almost exclusively the continuous ex-PTA process, and are reaching very high production capacities (180 to 300,000 t/year per line), which are constantly growing.

For standard applications, such as textile fibers and films, all polycondensation takes place in the melt phase. For other applications, such as industrial yarns and hollow bodies, which require very good mechanical properties, polyester must have a high molecular weight, which can only be achieved by solid-phase postcondensation (SPPC). PCS takes place at lower temperatures, limiting degradation reactions and enabling the required high degrees of polymerization to be achieved.

The presentation will also cover the latest innovations in the PCS field, in particular those proposed by DuPont.

Lastly, we'll be taking a closer look at PET recycling, whose chemical and thermomechanical characteristics make this type of recovery possible.