History and Discovery

Polycarbonate was accidentally discovered by American chemist Daniel Fox at General Electric in 1953. He was trying to make polyesters but produced polycarbonate instead. The first polycarbonate products were introduced into the market under the brand name Lexan in the early 1960s. Since then, polycarbonate production has ramped up significantly and it has replaced other materials in many applications due to its superior characteristics.

Manufacturing Process

Polycarbonate is produced by the reaction between bisphenol A (BPA) and phosgene in an interfacial polymerization process. BPA and phosgene dissolved in aqueous and organic solvents are contacted together at the interface under controlled temperature and reaction conditions. This leads to the formation of long carbonate chains as the polymer product. The polycarbonate molecules are further purified, dried and granulated for industrial use.

Physical and Chemical Properties

Some key physical and chemical properties of polycarbonate that make it a versatile engineering plastic include:

- High impact strength even at low temperatures down to -25°C.

- Transparency - Polycarbonate has up to 90% light transmission which makes it a good substitute for glass.

- Self-extinguishing - It has a high burning rate but stops burning immediately when the flame source is removed.

- Chemical resistance - Polycarbonate is resistant to acids, alkalis, salt solutions and aliphatic hydrocarbons at room temperature.

- Weatherability - It has excellent UV resistance and retains mechanical properties even after prolonged outdoor exposure.

- Recyclable - Polycarbonate scrap can be reused and melted down in the manufacturing process.

Engineering Applications

Due to the comprehensive material properties, Polycarbonate finds widespread use in a variety of engineering applications:

Consumer Electronics: Polycarbonate is widely used in consumer electronic device housings and components that require impact resistance as well as transparent parts. It is a preferred material for smartphone screens, laptops, TVs, etc.

Automotive: Headlight lenses, taillight lenses, interior panels, instrument panels are commonly made of polycarbonate in modern vehicles due to its high durability and safety characteristics.

Medical Devices: Polycarbonate is biocompatible so it is used to make medical equipment housings, devices for dialysis, test tubes, syringes etc. Its clarity is beneficial for parts that need visualization.

Construction: Architectural glazing (non-glass walls, skylight domes), roofing panels make use of polycarbonate’s high strength, transparency and UV resistance outdoors.

Safety Equipment: Riot shields, safety glasses, face shields, bullet proof glass, helmet visors are examples where polycarbonate provides ballistic protection along with optical clarity.

Electrical/Electronics: As an insulator, polycarbonate films and molded parts find application in switchgear, junction boxes, plugs etc. due to its self-extinguishing property.

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