Acrylic and Plexiglass are often used interchangeably in product literature concerning sheet plastic. While Plexiglass is made from acrylic, there are subtle differences, which can be important depending on the application. While Plexiglas is a trade or brand name, there is a difference in the way it is manufactured compared to standard acrylic.
Acrylic is manufactured in one of two ways. It is either extruded or cell cast. The extrusion method is a less expensive way to manufacture acrylic but presents two problems. Extruded acrylic is softer than cell cast acrylic, which means it is more susceptible to scratching. And extruded acrylic can have impurities in its surface. Cell cast acrylic has a harder surface because of the casting process. When acrylic is cell cast it is formed in a closed area, which reduces the chances of impurities becoming lodged in the material.
Plexiglas is the original trade or brand name for this type of acrylic. Plexiglas is a cell cast acrylic, so it has fewer impurities (tiny ripples or embedded specks). The manufacturing costs are higher with cast acrylic, which is reflected in its higher price. The term Plexiglass is more commonly used for this type of acrylic.
The primary mechanical difference between extruded acrylic and Plexiglass is its surface hardness. Standard extruded acrylic is softer, making it ideal for gluing pieces of this material together. However, softer material tends to crack or chip when drilling or cutting it. Plexiglass has a harder surface so cracking becomes less of an issue. The surface is more resistant to chemicals, including solvent cements used for gluing Plexiglass together.
Trade or Brand Names
The most confusing issue about acrylic and Plexiglass are the numerous names used in the plastics industry. Acrylic is a parent name that indicates the type of polymer used in its manufacturing. Plexiglas is a trade or brand name. It's more often called Plexiglass. Plexiglass is a common term used for cell cast acrylic (as is Lucite and Arcylite). If you walk into a store and ask for acrylic, you may get whatever the store commonly sells. Even using the word "Plexiglass" does not guarantee you will get the correct product. It is better to refer to this material as either extruded acrylic or cell cast acrylic. Using the proper terms and knowing the differences between the two ensures you'll get the right materials.
Fading and Discoloration
The limited warranty of most acrylic-based plastics is 7 to 10 years. This limited warranty covers fading and discoloration. This does not mean this material will last a full 10 years. If you live in an area with high salt content in the air (near a beach), the material may start to show signs of fading or discoloration sooner. The same applies to materials that come in contact with chemicals such as alcohol and ammonia. In general, the harder the surface, the most resistant the material is to these environmental factors.