POLYMETHYL METHACRYLATE (PMMA)
Poly (methyl methacrylate) (PMMA) is a transparent thermoplastic, often used as a light or shatter-resistant alternative to glass. It is sometimes called acrylic glass.
Chemically, it is the synthetic polymer of methyl methacrylate.
PMMA is an economical alternative to polycarbonate (PC) when extreme strength is not necessary. Additionally, PMMA does not contain the potentially harmful bisphenol-A subunits found in polycarbonate.
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, and is more prone to scratching compared to conventional inorganic glass.
More information available at http://en.wikipedia.org/wiki/Poly (methyl_methacrylate)