PMMA Plexiglass is often used as an alternative to glass, and in competition with polycarbonate (PC). It is often preferred because of its moderate properties, easy handling and processing, and low cost, but behaves in a brittle manner when loaded, especially under an impact force. To produce 1 kg of PMMA, about 2 kg of petroleum is needed. PMMA ignites at 460°C and burns completely to form only carbon dioxide and water.

The first acrylic acid was created in 1843. Methacrylic acid, derived from acrylic acid, was formulated in 1865. The reaction between methacrylic acid and methyl alcohol results in the ester methyl methacrylate. The German chemists Fittig and Paul discovered in 1877 the polymerization process that turns methyl methacrylate into polymethyl methacrylate. In 1933 the German chemist Otto Röhm patented and registered the brand name PLEXIGLAS. In 1936 the first commercially viable production of acrylic safety glass began. During World War II acrylic glass was used for submarine periscopes, and windshields, canopies, and gun turrets for airplanes.

Some glass substitute uses:

• PMMA Acrylic glass is commonly used for constructing residential and commercial aquariums.
• PMMA is used in the lenses of exterior lights of automobiles.
• The spectator protection in ice hockey stadiums is made from PMMA.
• Motorcycle helmet visors
• Police vehicles for riot control often have the regular glass replaced with acrylic to protect the occupants from thrown objects.
• Acrylic is used for viewing ports and even complete hulls of submersibles, such as the Alicia submarine's viewing spheres and the Bathyscaphe Trieste's windows.
• Polycast acrylic sheet is the most widely used material in aircraft transparencies (windows). In applications where the aircraft is pressurized, stretched acrylic is used.
• Acrylic is an important material in the making of certain lighthouse lenses.

Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)