Acrylic is the most common name for polymethyl methacrylate. Acrylic is a so-called thermoplastic, which means that it becomes softer when heated. Acrylic sheets are an ideal substitute for glass because they are 30 times more impact resistant. The substance is also known under brandnames Perspex® or Altuglas®.
Replacement for glass
Acrylic can be manufactured in the most diverse forms. It is an ideal replacement for glass because it offers great advantages. In the first place, acrylic sheet weighs much less than glass, it is 50% lighter. Acrylic sheets are also much more resistant to impact, at least 30 times more impact-resistant than glass. If acrylic breaks, it doesn’t splinter like glass, but with a single break. A third advantage of acrylic sheets is that they allow more light through than glass, with a light transmittance of 90%. Certainly, with larger sheet thicknesses, this plastic noticeably lets more light through than glass of the same thickness.
Almost a century old
The production of acrylic began in the 1930s: in 1936, it was first marketed by the American company Rohm and Haas. The base materials are sulphuric acid, hydrogen cyanide, methanol and acetone. Not the safest substances, but the end product is completely harmless. Acrylic sheet is flammable, but when it burns, doesn’t form any harmful substances at all. The residual products are carbon dioxide and water.
There are also some disadvantages to acrylic: we’ve already mentioned that the material deforms under the influence of high temperatures. It isn’t heat-resistant and so can’t be used for safety applications such as glazing in vehicles for passenger transport. Because of its weight, strength and relatively low price, acrylic sheets are often used for glazing large surfaces, such as wind and noise barriers. Because of its strength, acrylic is widely used in very large aquariums and ponds in zoos. They require a glass thickness of up to 30 centimetres so if ordinary glass were used for this, the transparency would be too low and the glazing would also be much too heavy.
Points to note when buying
There are two types of acrylic sheet available on the market, cast and extruded types. These are also called acrylic GS (cast) or acrylic XT (extruded); the cast version is poured into a flat plate after the production process while the extruded type is rolled to thinner thicknesses after pouring. When the thickness is reduced, the plate surface increases, making it easier to make a larger sheet. The disadvantage is that the stresses in the sheet material increase, so during machining, extruded sheets will break and crack easily – these are sold as ‘cheap acrylic sheets‘.