Polycarbonate
| Polycarbonate | |
|---|---|
Repeating chemical structure unit of
Polycarbonate made from bisphenol A  |
|
| Physical Properties | |
| Density (ρ) | 1.20–1.22 g/cm3 |
| Abbe number (V) | 34.0 |
| Refractive index (n) | 1.584–1.586 |
| Flammability | V0-V2 |
| Limiting oxygen index | 25–27% |
| Water absorption—Equilibrium (ASTM) | 0.16–0.35% |
| Water absorption—over 24 hours | 0.1% |
| Radiation resistance | Fair |
| Ultraviolet (1–380 nm) resistance | Fair |
| Mechanical Properties | |
| Young's modulus (E) | 2.0–2.4 GPa |
| Tensile strength (σt) | 55–75 MPa |
| Elongation (ε) at break | 80–150% |
| Compressive strength (σc) | >80 MPa |
| Poisson's ratio (ν) | 0.37 |
| Hardness—Rockwell | M70 |
| Izod impact strength | 600–850 J/m |
| Notch test | 20–35 kJ/m2 |
| Abrasive resistance ASTM D1044 | 10–15 mg/1000 cycles |
| Coefficient of friction (μ) | 0.31 |
| Speed of sound | 2270 m/s |
| Thermal Properties | |
| Glass transition temperature (Tg) | 147 °C (297 °F) |
| Heat deflection temperature |
|
| Vicat softening point at 50 N | 145–150 °C (293–302 °F) |
| Upper working temperature | 115–130 °C (239–266 °F) |
| Lower working temperature | −40 °C (−40 °F) |
| Thermal conductivity (k) at 23 °C | 0.19–0.22 W/(m·K) |
| Thermal diffusivity (a) at 25 °C | 0.144 mm²/s |
| Linear thermal expansion coefficient (α) | 65–70 × 10−6/K |
| Specific heat capacity (c) | 1.2–1.3 kJ/(kg·K) |
| Electrical Properties | |
| Dielectric constant (εr) at 1 MHz | 2.9 |
| Permittivity (ε) | 2.568 × 10−11F/m |
| Relative permeability (μr) at 1 MHz | 0.866(2) |
| Permeability (μ) at 1 MHz | 1.089(2) μN/A2 |
| Dissipation factor at 1 MHz | 0.01 |
| Surface resistivity | 1015Ω/sq |
| Volume resistivity (ρ) | 1012–1014Ω·m |
| Chemical Resistance | |
| Acids—concentrated | Poor |
| Acids—dilute | Good |
| Alcohols | Good |
| Alkalis | Good-Poor |
| Aromatic hydrocarbons | Poor |
| Greases & Oils | Good-fair |
| Halogenated Hydrocarbons | Good-poor |
| Halogens | Poor |
| Ketones | Poor |
| Gas permeation at 20 °C | |
| Nitrogen | 10–25 cm3·mm/(m2·day·Bar) |
| Oxygen | 70–130 cm3·mm/(m2·day·Bar) |
| Carbon dioxide | 400–800 cm3·mm/(m2·day·Bar) |
| Water vapour | 1–2 gram·mm/(m2·day) @ 85%–0% RH gradient |
| Economics | |
| Price | 2.6–2.8 €/kg |
Polycarbonates (PC) are a group of thermoplastic polymers containing carbonate groups in their chemical structures. Polycarbonates used in engineering are strong, tough materials, and some grades are optically transparent. They are easily worked, molded, and thermoformed. Because of these properties, polycarbonates find many applications. Polycarbonates do not have a unique resin identification code (RIC) and are identified as "Other", 7 on the RIC list. Products made from polycarbonate can contain the precursor monomer bisphenol A (BPA). Polycarbonate is also known by a variety of trademarked names, including Lexan, Makrolon, Hammerglass and others.
Polycarbonates received their name because they are polymers containing carbonate groups (−O−(C=O)−O−). A balance of useful features, including temperature resistance, impact resistance and optical properties, positions polycarbonates between commodity plastics and engineering plastics.
The main polycarbonate material is produced by the reaction of bisphenol A (BPA) and phosgene COCl
2. The overall reaction can be written as follows:
The first step of the synthesis involves treatment of bisphenol A with sodium hydroxide, which deprotonates the hydroxyl groups of the bisphenol A.
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