High impact resistance and excellent transparency make polycarbonate the material of choice for water bottles, windshields, and eyeglasses.
In 1953, polycarbonate resin was invented twice. It was first created in Germany by Dr. Hermann Schnell of Bayer, and then, just one week later in the United States, Dr. Daniel Fox of General Electric announced his discovery. Both companies applied for a patent for the gooey substance, which hardened into a nearly unbreakable solid. Both companies agreed that whichever received the patent would pay a royalty to the other, which allowed Bayer and GE to each develop and market products based on the resin.
Polycarbonate is a thermoplastic, which is a class of polymers that turn to liquid at higher temperatures and solidify into a glass-like phase when cooled. Polycarbonates tend to begin to soften around 150 ˚C and liquefy around 300 ˚C. In spite of this property, polycarbonates are often worked at room temperature using processes similar to those used for sheet metals since polycarbonates are able to withstand large amounts of stress without cracking or breaking.
Polycarbonate has two especially valuable properties: it is highly impact resistant and extremely transparent to visible light. Unfortunately, polycarbonate is easily scratched, but with a protective coating it may be used for sunglasses, eyeglasses, automotive headlight lenses, and sports helmets. A different coating is used to make the bullet-resistant glass in cars and the bullet-proof glass that protects bank tellers. Polycarbonate was even used in the bubble helmets worn by the Apollo astronauts when they walked on the moon.
Polycarbonate is also much more commonly known. It is the polymer that makes up the containers that hold many commercial, bottled waters and also CDs, DVDs, and Blu-ray discs. Polycarbonate is marketed under the trade names Lexan and Makralon.