Polycarbonate

Polycarbonate
Physical Properties
Density	1200-1220 kg/m³
Abbe number	34.0
Refractive index	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 G Pa
Tensile strength (σ_t₎	55-75 M Pa
Compressive strength (σ_c₎	>80 M Pa
Elongation @ break	80-150%
Poisson's ratio	0.37
Hardness - Rockwell	M70
Izod impact strength	600-850 J/m
notch test	20-35 k J/m²
Abrasive resistance - ASTM D1044	10-15 m g/1000 cycles
Coefficient of friction	0.31
Thermal Properties
Melting temperature (T_m)	267°C*
Glass transition temperature(T_g)	150°C
Heat Deflection Temperature - 10 k N(Vicat B)	145°C
Heat Deflection Temperature - 0.45 M Pa	140°C
Heat Deflection Temperature - 1.8 M Pa	128-138°C
Upper working temperature	115-130°C
Lower working temperature	-135°C
Linear thermal expansion coefficient (α)	65-70 x10^-6/K
Specific heat capacity (c)	1.2-1.3 k J/kg·K
Thermal conductivity @ 23°C	0.19-0.22 W/(m·K)
Heat transfer coefficient (λ)	0.21 W/(m²·K)
Electrical Properties
Dielectric constant @ 1 M Hz	2.9
Dielectric strength	15-67 k V/mm
Dissipation factor @ 1 M Hz	0.01
Surface Resistivity	10¹⁵ Ohm/sq
Volume Resistivity	10¹²-10¹⁴ Ohm·m
Chemical Resistance
Acids - concentrated	Good
Acids - dilute	Good
Alcohols	Good
Alkalis	Good-Poor
Aromatic hydrocarbons	Poor
Greases & Oils	Good-Fair
Halogenated Hydrocarbons	Good-Poor
Halogens	Poor
Ketones	Poor
Economical Properties
Price	5-9 €/kg
# Deformation temperature at 10kN needle load Source: A.K. vam der Vegt & L.E. Govaert, Polymeren, van keten tot kunstof, ISBN 90-407-2388-5 Marchant RE, Wang I (1994). Physical and chemical aspects of biomaterials used in humans. in ISBN 0849344328

Polycarbonates are a particular group of thermoplastics. They are easily worked, molded, and thermoformed; as such, these plastics are very widely used in modern manufacturing. They are called polycarbonates 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-esterificated with a diphenolic derivative affording poly(aromatic carbonate)s. Taking into consideration the C1-synthon we can devide polycarbonates on poly(aromatic carbonate)s and poly(aliphatic carbonate)s. The second one, poly(aliphatic carbonate)s are a product of the reactuion of carbon dioxide with epoxides, what 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 a very durable material, and can be laminated to make bullet-proof "glass", though “bullet-resistant” would be more accurate. 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 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

Polycarbonate is becoming more common in housewares as well as laboratories and in industry. It is often used to create protective features, for example in banks as well as vandal-proof windows and lighting lenses for many buildings. Other products made from polycarbonate include sunglass/eyeglass lenses, compact discs, DVDs, and automotive headlamp lenses. It is the major component of one variety of Nalgene bottles. It is also used for animal enclosures and cages used in research.

LEXAN® is the registered trademark for polycarbonate plastic manufactured (from Bisphenol A) by General Electric. MERLON® is the registered trademark used by the Mobay Chemical Company. MAKROLON® is the registered trademark for polycarbonate from Bayer, which is also referred to as "macrolon". PANLITE® is the registered trademark for polycarbonate plastic manufactured from Teijin Chemical Limited, which is also the major producer for optical grade polycarbonate.

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.

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.

Interaction with other chemicals

will damage Polycarbonate	require caution	are considered safe

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.

References

Plastics | Optical materials | Polycarbonates | dielectrics

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Potential hazards in food contact applications

Synthesis

Interaction with other chemicals

References