All acrylic sheets are made from MMA monomer, whose chemical name is methyl methacrylate. MMA monomer is a clear, transparent liquid that looks very much like water. To convert it into a solid material called a polymer, a catalyst must be added and the mixture heated.
Acrylic sheets are basically divided into two types: extruded sheets and cast sheets, which mainly refer to the processing technologies used in their manufacture. Extruded acrylic sheets have excellent thermoforming properties but are more brittle than cast sheets. Due to their poor crack resistance, chemical resistance, and resistance to hot water cycling, extruded sheets are not suitable for manufacturing bathtubs. Cast acrylic sheets are produced using liquid MMA: the MMA is poured into a glass mold cavity and polymerized into shape in a heated oven, a process known as “cavity casting”.
Sanitary ware-grade cast acrylic sheet is a special-grade sheet specifically designed for manufacturing bathtubs and other sanitary ware. It has the same high molecular weight as standard cast sheets but features cross-linking—a special chemical reaction that enhances the sheet’s resistance to household chemical cleaners and other solvents. Through careful selection of colorants, sanitary ware-grade sheets can also be dyed, ensuring that the entire surface of the final bathtubs has a uniform color that remains unchanged for many years. In contrast, ordinary acrylic sheets have poor hot water resistance; they tend to fade, lose their luster, and even crack.
It is a common misconception that plastics are inferior to traditional building materials, and people may also think that acrylic is prone to scratches. However, sanitary ware-grade acrylic sheet is one of the hardest plastics in common use. According to the ISO 2093/2 method, its Rockwell hardness is 102, and its Barcol hardness is 55. When using pencils to indicate hardness (a common testing method), sanitary ware-grade acrylic sheet has a hardness of 9H, which is comparable to that of polished aviation-grade aluminum.