High quality acrylic sheets. Perspex sheets are among the highest quality plastics manufactured in the world. These thermoplastic panels are often used as a lightweight alternative to glass and other materials because they offer excellent optical quality, high light transmission, weather resistance, and sound reflection. Like most plastics, plexiglass sheets respond to temperature changes by expanding or contracting at a far greater rate than glass. One major difference between acrylic and glass is that acrylic does not shrink with age. Some shrinkage may occur when general-purpose plexiglass is heated to forming temperature, but post-forming stability is exceptional.