How polycarbonate is made

Polycarbonate is a clear plastic built from a molecule called bisphenol A, joined by a carbonate link.

stations: 5
things upstream: 17
raw sources: 7
steps from the ground: 6

The short version

Polycarbonate is made by joining bisphenol A, a molecule made of phenol and acetone, to carbonate groups. In the main factory route, the bisphenol is first dissolved in caustic soda, then reacted with a chlorine-based reagent in a solvent. The polymer is washed, dried and extruded into clear pellets.

Make bisphenol A

Phenol and acetone, both made from propylene and benzene, are condensed into bisphenol A. Crystals are purified until they are very clean.

Goes in
Phenol Propylene Acetone
Dissolve it in lye

The bisphenol A is treated with sodium hydroxide, which prepares its hydroxyl groups to link up. This turns the crystals into a water-soluble salt.

Goes in
Caustic soda
Join it with the carbonate unit

The salt reacts with a chlorine-based carbonyl reagent made from chlorine. A closed, tightly controlled reactor grows the chains where water and solvent meet.

Goes in
Chlorine
Wash out the salts

The polymer solution is washed free of salt and leftover reagents. The solvent is then evaporated and recycled.
Extrude and pellet it

An extruder melts the polymer, filters it, and cuts it into clear pellets. Molders turn the pellets into lenses, sheet, headlight covers and discs.

End of the linePolycarbonate Next it goes into led light bulb, camera drone, eyeglass lens and 11 more.

Worth repeating

About 10 million tonnes of bisphenol A were produced worldwide in 2022.
Making polycarbonate is the largest single use of bisphenol A, accounting for 65 to 70% of all of it.
Polycarbonate is used instead of glass in some displays, though other screens still need glass for its higher melting temperature.