are a particular group of
Thermoplastic s. They are easily worked,
Molded , and
Thermoformed ; as such, these
Plastic s are very widely used in modern
Manufacturing . They are called '''polycarbonates''' because they are
Polymer s having functional groups linked together by
Carbonate Group s (-O-CO-O-) in a long molecular chain.
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 :
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 Disc s,
DVD s, 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 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
Polycarbonate can be synthesized from
Bisphenol A and
Phosgene (carbonyl dichloride, COCl
2). The first step in the synthesis of polycarbonate from bisphenol A is treatment of bisphenol A with
Sodium Hydroxide . This deprotonates the
Hydroxyl Group s 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/cm
3.
Using
Sodium Hydroxide and other alkali cleaners on polycarbonate is not recommended as they cause the release of
Bisphenol-A , a known
Endocrine disrupter.
