Polycarbonate

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Polycarbonates are a particular group of thermoplastics. belonging to the family polyeasters, they are produced via step polymerisation.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-CO-O-) in a long molecular chain. The beta transition occuring at -110 °C leads to increased toughness. Polycarbonate like other [amorphous] polymers do not have a Tm. As there are no crystals to melt.

The most common type of polycarbonate plastic is one made from [[Bisphenol A]and [phosgene]], 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 N/A°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.

Polycarbonate
Density	1220 kg/m³
Young's modulus(E)	2-2.2 G Pa
Tensile strength(σ_{t_)</td>}	60-65 M Pa
Elongation @ break	80-150%
notch test	20-35 k J/m^{2^</td></tr>}
Glass temperature	150°C
[[beta transition temperature]	-110°C
Melting temperature	n/a an amorphous polymer*	-
Vicat BTemplate:Ref	145
heat transfer coefficient (λ)	0.21 W/m.K
linear expansion coefficient (α)	6.5 10^{-5^/K</td></tr>}
Specific heat (c)	1.3 k J/kg.K
Water absorption (ASTM)	0.16
Price	5-9 €/kg
# Template:Note Deformation temperature at 10kN needle load </th></tr>
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

1 Potential hazards in food contact applications
2 Synthesis
3 Interaction with other chemicals
4 External link

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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. Howdeshell et. al. found that 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. http://ehp.niehs.nih.gov/members/2003/5993/5993.html

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 appear to tend to find no significant effects while government funded studies tend to find significant effects. http://ehp.niehs.nih.gov/docs/2005/7713/abstract.html

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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.

Image:Bisphenol A plus NaOH.PNG

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.

Image:Bisphenolate A plus Phosgene.PNG

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.

Image:Adding Bisphenolate A to Chloroformate.PNG

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.

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Interaction with other chemicals

will damage Polycarbonate	require caution	are considered safe
Acetone Acrylonitrile Ammonia Amyl acetate Benzene Bromine Butyl acetate Caustic soda Chloroform Dimethylformamide Concentrated Hydrochloric acid Concentrated Hydrofluoric acid Iodine Methanol Methyl ethyl ketone Styrene Tetrachloroethylene Toluol Concentrated Sulfuric acid Xylene	Cyclohexone 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% Mercury Methane Oxygen Ozone Sulphur Urea Water

Using Sodium hydroxide and other alkali cleaners on polycarbonate is not recommended as they cause the release of Bisphenol-A, a known endocrine disrupter.

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