Polycarbonate PC
Chemical composition
Section titled “Chemical composition”The repeating unit of standard polycarbonate (PC) has a molecular formula of (C₁₆H₁₄O₃)ₙ and is derived from the polycondensation of bisphenol A (BPA) with phosgene or diphenyl carbonate. The main chain contains carbonate groups (-O-CO-O-) bonded to aromatic rings that provide rigidity and transparency. Conductive grades may incorporate carbon fillers, such as carbon black, which modify the electrical resistivity without altering the base polymer structure.
Mechanical properties
Section titled “Mechanical properties”The tensile strength in injection-molded specimens ranges between 55 MPa and 75 MPa (8.0–10.9 ksi) depending on test speed and grade. Typical properties at room temperature (23 °C, as-supplied condition) are summarized below.
| Property | SI Value (min–max) | Imperial Value (min–max) | SI Unit | Imperial Unit |
|---|---|---|---|---|
| Tensile strength (σₜ) | 55–75 | 8.0–10.9 | MPa | ksi |
| Elongation at break (ε) | 80–150 | 80–150 | % | % |
| Young’s modulus (E) | 2.0–2.4 | 290–348 | GPa | 10³ ksi |
| Compressive strength (σc) | >80 | >11.6 | MPa | ksi |
| Rockwell hardness | M70 | M70 | – | – |
| Izod impact strength (notched) | 600–850 | 35.7–50.6 | J/m | ft·lb/in |
| Charpy impact strength (notched) | 20–35 | 11.9–20.8 | kJ/m² | ft·lb/in² |
| Coefficient of friction (μ) | 0.31 | 0.31 | – | – |
Physical properties
Section titled “Physical properties”The density of unreinforced polycarbonate is 1.20 g/cm³ (74.9 lb/ft³), while conductive grades with carbon filler can reach 1.38 g/cm³ (86.2 lb/ft³). It is an amorphous thermoplastic, transparent in the visible spectrum, with a light transmission of approximately 89 %.
| Property | SI Value | Imperial Value |
|---|---|---|
| Density (ρ) | 1.20–1.22 g/cm³ | 74.9–76.2 lb/ft³ |
| Water absorption (24 h, 23 °C) | 0.1 % | 0.1 % |
| Water absorption (equilibrium) | 0.16–0.35 % | 0.16–0.35 % |
| Refractive index (nD) | 1.584–1.586 | – |
| Speed of sound | 2270 m/s | 7450 ft/s |
| Abrasion resistance (Taber, CS‑17, 1000 cycles) | 10–15 mg | 0.00035–0.00053 oz |
Thermal properties
Section titled “Thermal properties”The glass transition temperature (Tg) of PC is 147 °C (297 °F), which defines its upper limit for structural use. The main thermophysical values are shown below.
| Property | SI Value | Imperial Value |
|---|---|---|
| Glass transition temperature (Tg) | 147 °C | 297 °F |
| Heat deflection temperature (HDT) at 0.45 MPa | 140 °C | 284 °F |
| HDT at 1.8 MPa | 128–138 °C | 262–280 °F |
| Continuous service temperature (upper) | 115–130 °C | 239–266 °F |
| Continuous service temperature (lower) | −40 °C | −40 °F |
| Coefficient of linear thermal expansion (α) | 65–70 × 10⁻⁶ /K | 36–39 × 10⁻⁶ /°F |
| Thermal conductivity (k) at 23 °C | 0.19–0.22 W/(m·K) | 1.32–1.53 BTU·in/(h·ft²·°F) |
| Specific heat (cp) | 1.2–1.3 kJ/(kg·K) | 0.29–0.31 BTU/(lb·°F) |
Electrical properties
Section titled “Electrical properties”Polycarbonate is an excellent electrical insulator, with a volume resistivity between 10¹² Ω·m and 10¹⁴ Ω·m under dry conditions. Its dielectric properties remain stable over a wide frequency and temperature range.
| Property | Value | Conditions |
|---|---|---|
| Dielectric constant (εr) | 2.9 | 1 MHz, 23 °C |
| Dissipation factor (tan δ) | 0.01 | 1 MHz, 23 °C |
| Surface resistivity | 10¹⁵ Ω/sq | 23 °C, 50 % RH |
| Volume resistivity (ρ) | 10¹²–10¹⁴ Ω·m | 23 °C, dry |
| Dielectric strength | 15–30 kV/mm | thickness 3.2 mm |
Chemical resistance
Section titled “Chemical resistance”PC exhibits moderate chemical resistance, being attacked by polar organic solvents and concentrated alkalis. Prolonged exposure to certain chemicals can cause environmental stress cracking (ESC). The following table summarizes its behavior towards common agents.
| Chemical agent | Resistance |
|---|---|
| Concentrated acids | Poor |
| Diluted acids | Good |
| Alkalis | Good – Poor (depending on concentration) |
| Alcohols | Good |
| Aromatic hydrocarbons | Poor |
| Ketones | Poor |
| Halogenated hydrocarbons | Good – Poor |
| Fats and oils | Good – Fair |
| Fresh water | Excellent |
| Seawater | Excellent |
| UV radiation (without protection) | Fair (yellowing) |
Applications by industry
Section titled “Applications by industry”Thanks to its unique combination of transparency, high impact strength and dimensional stability, polycarbonate is used in sectors where safety and durability are critical.
- Construction and architecture: safety glazing sheets, translucent roofs, canopies, acoustic barriers.
- Automotive and transportation: headlights, interior and exterior optics, armored vehicle windows, high-strength interior components.
- Electronics and electrical: mobile device housings, CD/DVD/Blu‑ray substrates, connectors, distribution boxes.
- Security and defense: helmet visors, riot shields, ballistic protective eyewear, aircraft windows.
- Medical and laboratory: sterilizable equipment (autoclave at 121 °C), medical device housings, BPA-free connectors for specific applications (special grades).
- Consumer and household: reusable bottles, kitchen utensils, ophthalmic lenses, appliance housings.
Comparison with similar materials
Section titled “Comparison with similar materials”Compared to other transparent thermoplastics, PC offers the best impact resistance (up to 30 times greater than glass and 10 times greater than PMMA). Compared to poly(methyl methacrylate) (PMMA), PC is tougher and withstands higher temperatures, although PMMA offers better surface scratch resistance and weathering without UV protection. Regarding ABS, PC is transparent, stiffer, and more heat resistant, while ABS provides lower cost and better processability. Compared to tempered glass, PC weighs less than half, is virtually unbreakable and can be thermoformed, although its scratch and chemical resistance is inferior.
| Material | Density (g/cm³) | Tensile strength (MPa) | Izod impact strength (J/m) | Transparency | Maximum service temperature (°C) |
|---|---|---|---|---|---|
| Polycarbonate (PC) | 1.20 | 55–75 | 600–850 | Yes, excellent | 115–130 |
| PMMA (acrylic) | 1.19 | 65–75 | 15–25 | Yes, excellent | 70–90 |
| ABS | 1.04–1.06 | 35–50 | 200–400 | Opaque (transparent in special grades) | 80–100 |
| Tempered glass | ~2.5 | 40–120 (flexure) | Brittle | Yes | >200 |
Machining and processing
Section titled “Machining and processing”Polycarbonate can be processed by injection, extrusion, thermoforming and blow molding, with injection molding being the most widespread method. For chip-removal machining (turning, milling, drilling), it is recommended to use sharp-edged tools, ample cooling and low cutting speeds to avoid overheating and stress cracking. The material requires thorough pre-drying (4 h at 120 °C) to remove moisture and prevent hydrolytic degradation during processing. Machined parts may require subsequent annealing at 120–130 °C to relieve internal stresses.
Nomenclature and designations
Section titled “Nomenclature and designations”In the industrial field, polycarbonate is recognized by the acronym PC according to ISO 1043‑1 and ASTM D7611. Some widely known trade names are Lexan™ (SABIC), Makrolon® (Covestro), Panlite® (Teijin) and Calibre™ (Trinseo). Specific grades include general purpose, flame retardant (V‑0, V‑2), UV-stabilized, glass fiber reinforced (PC‑GF) and blends such as PC/ABS or PC/PBT for engineering applications.
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What is the typical density of polycarbonate?
Section titled “What is the typical density of polycarbonate?”The density of standard unreinforced polycarbonate is 1.20 g/cm³ (74.9 lb/ft³), reaching up to 1.22 g/cm³ in some grades and up to 1.38 g/cm³ in conductive versions with carbon filler.
What impact strength does PC offer compared to other plastics?
Section titled “What impact strength does PC offer compared to other plastics?”Polycarbonate exhibits an Izod impact strength between 600 J/m and 850 J/m (11–16 ft·lb/in), making it one of the toughest thermoplastics, exceeding glass by more than 30 times and polymethyl methacrylate (PMMA) by about 10 times.
Up to what temperature can polycarbonate work continuously?
Section titled “Up to what temperature can polycarbonate work continuously?”The continuous service temperature in air ranges from 115 °C to 130 °C (239–266 °F), while the glass transition temperature (Tg) is 147 °C (297 °F), marking the limit of structural rigidity.
Is polycarbonate resistant to ultraviolet radiation?
Section titled “Is polycarbonate resistant to ultraviolet radiation?”Without protection, polycarbonate has fair UV resistance and tends to yellow with prolonged outdoor exposure. Grades stabilized by coextrusion or UV-absorbing additives significantly improve long-term performance, being classified as “UV-resistant”.
What chemicals damage polycarbonate?
Section titled “What chemicals damage polycarbonate?”PC is attacked by concentrated acids, ketones, aromatic hydrocarbons, and some concentrated alkalis. Conversely, it shows good resistance to diluted acids, alcohols, fats and oils, as well as fresh and salt water.
What is the thermal conductivity of polycarbonate?
Section titled “What is the thermal conductivity of polycarbonate?”The thermal conductivity of PC at 23 °C is low, with a value of 0.19–0.22 W/(m·K) (1.32–1.53 BTU·in/(h·ft²·°F)), making it an effective thermal insulator suitable for glazing applications requiring energy control.
References
Section titled “References”- azom.com: https://www.azom.com/properties.aspx?ArticleID=2008
- engineeringtoolbox.com: https://www.engineeringtoolbox.com/polymer-properties-d_1222.html
- steelnumber.com: https://www.steelnumber.com/en/steel_composition_eu.php?name_id=591