Many people believe that plexiglass is a member of the glass family. This is because it has excellent light transmission and a smooth, glossy appearance, which makes it look very similar to glass. However, the composition of plexiglass is completely different from that of glass, and many of its properties are also different. The raw materials of ordinary glass are mainly soda ash, limestone, and quartz sand, which are all inorganic compounds; while plexiglass is a polymer made from a type of organic compound called methyl methacrylate. It is only because it resembles glass that it is given the popular name "plexiglass". Apart from their similar appearance, ordinary glass and plexiglass also share some properties, such as their amorphous, glass-like characteristics, and the fact that they both become soft and even flowable when heated to a certain temperature, etc.
However, ordinary glass has a high density, is hard and heavy, prone to breakage, and difficult to deform, and can hardly be dissolved in various solvents. Although plexiglass resembles glass in appearance, it is the opposite of ordinary glass in these properties. The density of plexiglass is half that of ordinary glass, making it lighter; it is not as hard, but not as prone to breaking; it is easily deformed when heated, so it can be easily shaped into various forms and maintain its shape after returning to room temperature; and because it is an organic compound, it can be dissolved in organic solvents such as chloroform and can even burn in the air.
Taking the commonly used triangular ruler or straightedge as an example, they are usually made of plexiglass. Because plexiglass has excellent light transmission and is much lighter than ordinary glass, it is very convenient and lightweight to use. Even if it is accidentally dropped on the ground, it is not easy to break. However, these rulers are prone to surface discoloration due to long-term friction, which is because plexiglass is not as wear-resistant as ordinary glass, which is also a disadvantage of plexiglass.