Poly(methyl methacrylate) (PMMA) is a transparent thermoplastic often used as a lightweight or shatter-resistant alternative to soda-lime glass. Although not a type of familiar silica-based glass, the substance, like many thermoplastics, is often technically a type of glass (a non-crystalline vitreous substance) and historically has often been called acrylic glass. Chemically, it is the synthetic polymer of methyl methacrylate. The material was developed in 1928 in several different laboratories by many chemists such as William Chalmers, Otto Röhm and Walter Bauer and was first brought to market in 1933 by the Rohm and Haas Company, under the trademark Plexiglas. It has since been sold under many different names, including Acrylite, Lucite, and Perspex. 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. Non-modified PMMA behaves in a brittle manner when loaded, especially under an impact force, and is more prone to scratching than conventional inorganic glass, but modified PMMA can achieve high scratch and impact resistance.