Polycarbonate

Polycarbonate
Physical Properties
Density (ρ)	1200-1220 kg/m³
Abbe number (V)	34.0
Refractive index (n)	1.584-6
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 (1-380nm) resistance	Fair
Mechanical Properties
Young's modulus (E)	2-2.4 GPa
Tensile strength (σt)	55-75 MPa
Compressive strength (σc)	>80 MPa
Elongation (ε) @ break	80-150%
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
Thermal Properties
Melting temperature (Tm)	267°C*
Glass transition temperature(Tg)	150°C
Heat Deflection Temperature - 10 kN (Vicat B)	145°C
Heat Deflection Temperature - 0.45 MPa	140°C
Heat Deflection Temperature - 1.8 MPa	128-138°C
Upper working temperature	115-130°C
Lower working temperature	-135°C
Linear thermal expansion coefficient (α)	65-70 × 10-6/K
Specific heat capacity (c)	1.2-1.3 kJ/kg·K
Thermal conductivity (k) @ 23°C	0.19-0.22 W/(m·K)
Heat transfer coefficient (h)	0.21 W/(m²·K)
Electrical Properties
Dielectric constant (εr) @ 1 MHz	2.9
Permittivity (ε) @ 1 MHz	2.568 x10-11 F/m
Relative Permeability (μr) @ 1 MHz	0.866(2)
Permeability (μ) @ 1 MHz	1.089(2) μN/A²
Dielectric strength	15-67 kV/mm
Dissipation factor @ 1 MHz	0.01
Surface Resistivity	1015 Ω/sq
Volume Resistivity (ρ)	1012-1014 Ω·m
Near to Short-wave Infrared Transmittance Spectrum
Polycarbonate transmittance in 5/6 of the NIR & 1/5 of the SWIR regions. Also, polycarbonate is almost completely transparent throughout the entire visible region of the spectrum and very sharply cuts off to ~0% transmission at almost exactly 400 nm, blocking all UV light transmission.
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
Economic Properties
Price	5-9 €/kg

Polycarbonates are a particular group of thermoplastic polyesters. They are easily worked, molded, and thermoformed; as such, these plastics are very widely used in modern manufacturing. Their interesting features (temperature resistance, impact resistance and optical properties) positions them between commodity plastics and engineering plastics.

Chemistry

Polycarbonates got their name because they are polymers having functional groups linked together by carbonate groups (-O-(C=O)-O-) in a long molecular chain. Also carbon monoxide was used as a C1-synthon on an industrial scale to produce diphenyl carbonate, being later trans-esterified with a diphenolic derivative affording poly(aromatic carbonate)s. Taking into consideration the C1-synthon we can divide polycarbonates into poly(aromatic carbonate)s and poly(aliphatic carbonate)s. The second one, poly(aliphatic carbonate)s are a product of the reaction of carbon dioxide with epoxides, which owing to the thermodynamical stability of carbon dioxide requires the use of catalyst. The working systems are based on porphyrins, alkoxides, carboxylates, salens and beta-diiminates as organic, chelating ligands and aluminium, zinc, cobalt and chromium as the metal centres. Poly(aliphatic carbonate)s display promising characteristics, have a better biodegradability than the aromatic ones and could be employed to develop other specialty polymers.

The most common type of polycarbonate plastic is one made from bisphenol A, in which groups from bisphenol A are linked together by carbonate groups in a polymer chain. This polycarbonate is characterized as a very durable material, and can be laminated to make bullet-proof "glass", though “bullet-resistant” would be more accurate. Although polycarbonate has high impact-resistance, it has low scratch-resistance and so a hard coating is applied to polycarbonate eye-wear lenses. The characteristics of polycarbonate are quite like those of polymethyl methacrylate (PMMA; acrylic), but polycarbonate is stronger and more expensive. This polymer is highly transparent to visible light and has better light transmission characteristics than many kinds of glass. CR-39 is a specific polycarbonate material — although it is usually referred to as CR-39 plastic — with good optical and mechanical properties, frequently used for eyeglass lenses.

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%
• poor weathering in an ultraviolet (UV) light environment

Applications

Main transformation techniques for Polycarbonate resins are:

• injection moulding into ready articles
• extrusion into tubes, rods and other profiles
• extrusion with calenders into sheet (1-15 mm) and film (below 1 mm), which can be used as such, or manufactured into other shapes using thermoforming or secondary fabrication techniques, such as bending, drilling, routing, laser cutting etc.

Polycarbonate is becoming more common in housewares as well as laboratories and in industry, mainly where at least two of its three main features are required: high impact resistance, temperature resistance and optical properties. Typical injected applications are : lighting lenses sunglass/eyeglass lenses, compact discs, DVDs, automotive headlamp lenses, Nalgene bottles. It is also used for animal enclosures and cages used in research.

Typical sheet/film applications are:

• Industry: machined or formed, cases, machine glazing, riot shields, visors, instrument panels
• Advertisement: Signs, displays, poster protection
• Building : domelights, flat or curved glazing, sound walls,

Remark : for use in applications exposed to weathering or UV-radiation, a special surface treatment is needed. This either can be a coating (e.g. for improved abrasion resistance), or a coextrusion for enhanced weathering resistance.

Most common resins are LEXAN® from General Electric, CALIBRE® from DOW Chemicals, MAKROLON® from Bayer and PANLITE® from Teijin Chemical Limited. Being based on bisphenol A--a phenol based on benzene--pricing is largely dependent on phenol and benzene pricing.

Potential hazards in food contact applications

Polycarbonate may be appealing to fabricators and purchasers of food storage containers due to its clarity and toughness. Polycarbonate has been described as lightweight and highly break resistant particularly when compared to silica glass. Polycarbonate may be seen in the form of single use and refillable plastic water bottles.

More than 100 studies have explored the bioactivity of bisphenol A leachates from polycarbonates. Bisphenol A appeared to be released from polycarbonate animal cages into water at room temperature and that it may have been responsible for enlargement of the reproductive organs of female mice.

An analysis of the literature on bisphenol A leachate low-dose effects by vom Saal and Hughes published in August 2005 seems to have found a suggestive correlation between the source of funding and the conclusion drawn. Industry funded studies tend to find no significant effects while government funded studies tend to find significant effects.

Research by Ana M. Soto, professor of anatomy and cellular biology at Tufts University School of Medicine, Boston, published Dec. 6 in the online edition of Reproductive Toxicology (DOI: 10.1016/j.reprotox.2006.10.002) describes exposure of pregnant rats to bisphenol A at 2.5 to 1,000 µg per kg of body weight per day. At the equivalent of puberty for the pups (50 days old), about 25% of their mammary ducts had precancerous lesions, some three to four times higher than unexposed controls. The study is cited as evidence for the hypothesis that environmental exposure to bisphenol A as a fetus can cause breast cancer in adult women. http://pubs.acs.org/cen/news/84/i50/8450bisphenol.html Retrieved on 2007-02-26.

One point of agreement among those studying polycarbonate water and food storage containers may be that using sodium hypochlorite bleach and other alkali cleaners to clean polycarbonate is not recommended, as they catalyze the release of the Bisphenol-A. The tendency of polycarbonate to release bisphenol A was discovered after a lab tech used strong cleaners on polycarbonate lab containers. Endocrine disruption later observed on lab rats was traced to exposure from the cleaned containers.

A chemical compatibility chart shows reactivity between chemicals such as polycarbonate and a cleaning agent.[1][2] Alcohol is one recommended organic solvent for cleaning grease and oils from polycarbonate.[3] For treating mold, Borax:H₂O 1:96 to 1:8 may be effective.

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 carbonyl addition to create a tetrahedral intermediate (not shown here), after which the negatively charged oxygen kicks off a chloride ion (Cl^-) 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. Density starts at about 1.20 g/cm³.

Polycarbonate

Photo: Injection moulded safety spectacles.

Uses: Light diffusers, skylights, riot shields, machine guards, safety spectacles, signs and displays, aircraft interiors and electrical housings.

Note: Polycarbonate has high impact strength and has a good fire rating because it is self extinguishing.

Properties

Name Polycarbonate Thermoplastic yes Thermosetting yes Hardness hard Available in opaque colors yes Available as transparent yes Impact resistant yes Resistant to UV light yes Resistant to heat yes Flammable no Can be welded yes Can be glued yes Can be injection moulded yes Can be vacuum formed yes Can be strip bent yes

Interaction with other chemicals

will damage Polycarbonate	require caution	are considered safe
Acetone Acrylonitrile Ammonia Amyl acetate Benzene Bromine Butyl acetate Sodium hydroxide Chloroform Dimethylformamide Concentrated Hydrochloric acid Concentrated Hydrofluoric acid Iodine Methanol Methyl ethyl ketone Styrene Tetrachloroethylene Toluene Concentrated Sulfuric acid Xylene	alkali bleaches such as Sodium hypochlorite Cyclohexanone Diesel oil Formic acid Gasoline Glycerine Heating oil Jet fuel Concentrated Perchloric acid Sulfur dioxide Turpentine	Acetic acid Ammonium chloride Antimony trichloride Borax in H2O Butane Calcium chloride Calcium hypochlorite Carbon dioxide Carbon monoxide Citric acid 10% Copper sulphate Ethyl alcohol 95% Ethylene glycol Formaldehyde 10% Hydrochloric acid 20% Hydrofluoric acid 5% Isopropyl alcohol Mercury Methane Oxygen Ozone Sulphur Urea Water(1)

(1) At room temperature. At temperatures above 60°C hydrolysis is more present, degrading the plastic. Degradation depends on time and temperature.

Using sodium hypochlorite (bleach) and other alkali cleaners on polycarbonate is not recommended as they cause the release of bisphenol A, a known endocrine disrupter.