Were introduced in 1936 in the form of hard, rigid and transparent materials. Acrylics were used in World War II as aircraft canopies. Other applications include: lighting diffusers; outdoor signs; automobile tail lights; washbasins and sinks; safety shields; furniture (e.g., tables); skylights, and large-area enclosures for shopping centers, swimming pools, restaurants, etc., and as room dividers. The outstanding resistance to long-term exposure to sunlight and weathering is one of the more important characteristics of acrylic. Also notable is the exceptional clarity and good light transmission (cast acrylic sheet transmits about 92% total light). Acrylics are a family of thermoplastic resins of acrylic esters [CH2CHCOOR] or methacrylic esters [CH2C(CH3)COOR]. The acrylates may be methyl, ethyl, butyl, or 2-ethylhexyl. Usual methacrylates are the methyl, ethyl, butyl, laural and stearyl.