The polycarbonates are one of the relatively newer varieties of plastics. The name polycarbonate means a multiple derivative of carbonic acid, or more precisely, carbonic acid ester. The prototype of the polycarbonate family was born in 1898 in the laboratory of the German chemist Einhorn. It was a white, insoluble powder which melted with decomposition at temperatures above 100 °C. It was formed by the action of the poisonous gas phosgene on hydroquinone solutions. 30 years later, Carothers, the inventor of nylon, became interested in polycarbonates. Starting from other raw materials, he obtained polyesters of carbonic acid, which melt at a temperature of 50-60 °C. Finding them worthless, he devoted himself to further work on polyamides. It was not until the 1950s that work on polycarbonates began at the Bayer factory in Germany, at General Electric and at the Mobay Chemical Company (both in the USA). The raw materials were changed and selected over a long period of time until a new, highly valuable material was finally developed. 
[001] Polycarbonate sheets.
Polycarbonates are thermoplastics and can therefore be processed using conventional methods such as injection moulding or extrusion. Transparent polycarbonates have the appearance of a white powder. Their melting point is relatively high at 250-300 °C. When the powder is melted, it forms a colourless, perfectly transparent solid with high mechanical strength. From the point of view of the usability of polycarbonates, their durability and stability under the influence of factors such as radiation of different wavelengths, air at elevated temperatures (influence of oxygen), water and other corrosive environments is very important. According to a German study, polycarbonate sheets and profiles tested over several years have not changed in appearance or dimensions. One example of research - polycarbonate sheets after 27 hours of exposure to ultraviolet rays, after being kept for 26 weeks in the air at 150 °C, for 8 weeks at 170 °C and after 4-week standstill in water - did not change their dimensions or mechanical properties within measurable limits. Polycarbonate is resistant to neutral salt water solutions, mineral acid water solutions including nitric acid and hydrofluoric acid, it is also resistant to organic acid water solutions and strong oxidants, even in an acidic environment. Polycarbonates are less resistant to alkaline environments. 
[002] The canopy of a jet fighter. The base material is a polycarbonate. Polycarbonate film, being very robust and at the same time practically impermeable to gases and water, provides light and airtight packaging. It is also characterised by constant and temperature-independent insulating properties. This is important when the insulating properties of most plastics are highly dependent on temperature. The high heat resistance, combined with the ease of colouring polycarbonates into any colour and shade, gives these plastics a leading position in the manufacture of coloured filters such as cinema and theatre spotlights. 
[003] CD - compact disc. • • •
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