Molecule of the Month

August 2006: Lexan®

Lexan® is a hard plastic that was developed in 1953 by Dr. Daniel Fox at General Electric. He discovered its properties accidentally while trying to produce an insulation material for wires. Fox’s experiments yielded a gooey substance that, when hardened, was nearly unbreakable. It could be heated to the boiling point of water (100°C) without deforming, and it could be chilled to -40°C without fracturing.

Lexan® has been used to manufacture a variety of products where a hard, durable plastic is needed. It is twice as strong as ABS, PVC or polystyrene; and it generally costs twice as much. It can be made clear or it can be pigmented practically any color. Lexan® was used in the helmets worn by NASA astronauts. It has been used in everything from water bottles to bullet-proof windows. Today, one of its major uses is in CDs and DVDs.

Lexan® is GE’s trade mark, but the plastic’s generic name is polycarbonate. Chemically speaking, it is an ester formed between carbonic acid (H₂CO₃) and the hydroxyl (-OH) groups of phenols. Polycarbonate can be manufactured using a chemical reaction between phosgene and bisphenol A. The product is solid granules, which are later melted and cast into a mold.

Approximately three million tons of bisphenol A are manufactured worldwide each year, most of which is used to make polycarbonates.





Repeating structure of polycarbonate

bisphenol A

phosgene