A unique property of this thermoplastic is its ability to be shaped. Extruded acrylic is not as strong as cell cast, and tends to crack or splinter when being machined, so most higher quality products are made from cast acrylic. Structures can also be made with no seams, as chemical welding at the molecular level actually "melts" seams into one piece of solid material. Seams that are welded and polished correctly are invisible.
Misconceptions and Disadvantages
There are some misconceptions about acrylic, namely that it yellows, turns brittle, and cracks over time. Though this might be true of cheap forms of plastic, it is not so with acrylic. If taken care of, this material can remain new looking for several decades, regardless of age or exposure to sun. Some people worry that it scratches too easily, but unlike glass, scratches may be buffed out.
For all of its advantages, there are two disadvantages of acrylic: It is more expensive than glass, and if exposed to a direct flame, it will melt and eventually burn. Burning releases toxic fumes, so safety precautions should always be taken when it is being cut with power tools or bent using heat. When it is not cared for properly, or when inferior acrylic is used, it can scratch, and improperly made joints can be very visible.