Methyl Methacrylate (also known as MMA, methyl 2-methyl propenoate or 2-methylmethacrylate) is an ester of methacrylic acid. It has the formula C5H8O2 and is a clear, colourless liquid that has an acrid odour and is not known to occur naturally. It is insoluble in water, but is soluble in most organic solvents and it is also volatile and is flammable in both a liquid and vapour state. The principal application, consuming approximately 75% of the MMA, is the manufacture of polymethyl methacrylate acrylic plastics (PMMA).