Polycarbonates (PC) are a group of thermoplastic polymers containing carbonate groups in their chemical structures. They are known for their unique combination of properties, making them versatile materials used in various applications[1].
Structure and Production
Polycarbonates derive their name from the carbonate groups (-O-(C=O)-O-) in their polymer chains. The main production methods are:
- Phosgene route: Reaction of bisphenol A (BPA) with phosgene (COCl2)[1].
- Transesterification route: Reaction of BPA with diphenyl carbonate[1].
Properties
Polycarbonates exhibit a range of desirable properties:
- High impact resistance
- Optical transparency
- Temperature resistance
- Dimensional stability
- Electrical insulation
Key physical and mechanical properties include:
| Property | Value |
|---|---|
| Density | 1.20–1.22 g/cm³ |
| Refractive index | 1.584–1.586 |
| Young’s modulus | 2.0–2.4 GPa |
| Tensile strength | 55–75 MPa |
| Glass transition temperature | 147 °C (297 °F) |
Polycarbonates can undergo large plastic deformations without cracking or breaking, allowing for room temperature processing using sheet metal techniques[1].
Applications
Polycarbonates find use in numerous applications across various industries:
- Electronic components: Used in power systems and telecommunications hardware due to their electrical insulation properties[1].
- Construction: Employed in domelights, glazing, roofing sheets, and sound walls[1].
- 3D Printing: Extensively used in FDM printing for producing durable, strong plastic products[1].
- Data storage: Major application in the production of CDs, DVDs, and Blu-ray discs[1].
- Automotive and aircraft: Used in headlamp lenses, decorative bezels, and optical reflectors. The F-22 Raptor jet fighter’s cockpit canopy is made from high-quality polycarbonate[1].
- Security components: Used in bullet-resistant windows and barriers in banks[1].
- Consumer goods: Found in eyewear lenses, safety goggles, and sports equipment[1].
- Medical applications: Used in various medical devices, complying with ISO 10993-1 and USP Class VI standards[1].
- Mobile phones: Employed by manufacturers like Nokia, Samsung, and Apple in phone casings[1].
Processing Techniques
Main transformation techniques for polycarbonate resins include:
- Extrusion into tubes, rods, and profiles
- Sheet and film extrusion
- Injection molding
- Thermoforming[1]
History
Polycarbonates were first discovered in 1898 by Alfred Einhorn but were not commercialized until the 1950s. Key milestones include:
- 1953: Independent discoveries by Hermann Schnell (Bayer) and Daniel Fox (General Electric)
- 1958: Bayer begins commercial production under the name “Makrolon”
- 1960: GE starts production under the name “Lexan”[1]
Potential Hazards
The use of polycarbonate in food storage containers has been controversial due to the potential leaching of bisphenol A (BPA) at high temperatures. This has led to the development of “BPA-free” alternatives in various formulations[1].
In conclusion, polycarbonates are versatile materials with a wide range of applications across multiple industries. Their unique combination of properties, including high impact resistance, optical clarity, and temperature resistance, makes them valuable in many fields. However, concerns about BPA leaching have led to ongoing research and development of safer alternatives for food-contact applications.
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