Polycarbonates are a particular group of thermoplastics. They are easily worked, mold, and thermoformed; as such, these plastics are very widely used in modern manufacturing. They are called polycarbonates because they are polymers having monomers groups linked together by carbonate groups (-O-CO-O-) in a long molecular chain.

The most common type of polycarbonate plastic is one made from Bisphenol A, where groups from Bisphenol A are linked together by carbonate groups in a polymer chain. This polycarbonate is a very durable material, and can be laminated to make bullet-proof "glass", though “bullet-resistant” would be more accurate. The characteristics of polycarbonate are quite like those of polymethyl methacrylate (acrylic), but polycarbonate is stronger and thus more expensive. This polymer is mainly transparent and has better light transmission characteristics than glasses.

Polycarbonate has :

• a density of 1.20 g/cm³
• a use range from -100°C to +135°C
• a melting point around 250°C
• a refractive index equal to 1.585 ± 0.001
• a light transmission index equal to 90% ± 1%

Polycarbonate is becoming more common in housewares as well as laboratories or industries. It is often used to create protective features, for example in banks as well as vandal-proof windows and lighting lenses for many buildings. Other products made from polycarbonate include sunglass/eyeglass lenses and compact discs.

LEXAN® is the registered trademark for polycarbonate plastic manufactured (from Bisphenol A) by General Electric. MERLON® is the registered trademark used by the Mobay Chemical Company .

Synthesis

Polycarbonate can be synthesized from bisphenol A and phosgene (carbonyl dichloride, COCl₂). The first step in the synthesis of polycarbonate from bisphenol A is treatment of bisphenol A with sodium hydroxide. This deprotonates the hydroxyl groups of the bisphenol A molecule.

The deprotonated oxygen reacts with phosgene through a back-side attack to create a tetrahedral intermediate (not shown here) followed by elimination of a chloride ion (Cl^-) as a leaving group to form a chloroformate .

The chloroformate is then attacked by another deprotonated bisphenol A, eliminating the remaining chloride ion and forming a dimer of bisphenol A with a carbonate linkage in between.

Repetition of this process yields polycarbonate, a polymer with alternating carbonate groups and groups from bisphenol A. Polycarbonate is also widely known since it is a major material that makes up the popular Nalgene Bottles. Density starts at about 1.20 g/cm³.

External link

• European polycarbonate industry

---