methacrylates

Methacrylates are a class of esters derived from methacrylic acid. They are used both as monomers for polymerization and as specialty chemicals. The defining feature is the methacrylate group, with the general structure CH2=C(CH3)COOR, where R is an alkyl group. Common methacrylate monomers include methyl methacrylate (MMA), ethyl methacrylate, butyl methacrylate, and hydroxyethyl methacrylate (HEMA).

These monomers polymerize by free radical mechanisms to form poly(methacrylate) resins. The most widely produced is polymethyl methacrylate (PMMA), known for clarity and toughness. PMMA and copolymers are prepared by bulk, solution, or emulsion polymerization, and can be crosslinked for higher hardness. Industrial routes also employ esterification of methacrylic acid with various alcohols to yield different methacrylate esters.

Applications span plastics, coatings, adhesives, dental and medical materials, and optical uses. PMMA is used as a glass substitute, in lighting diffusers and lenses; methacrylate resins are also employed in dental acrylics and bone cements. Other methacrylates are used in specialty coatings, electronics encapsulants, and sealants.

Safety and handling: methacrylate monomers are reactive and can be skin sensitizers and irritants. They are typically stored with inhibitors to prevent premature polymerization. Residual monomer in polymers may pose health or environmental concerns; appropriate controls and ventilation are required during processing.

Environmental considerations: methacrylates and PMMA are relatively persistent in the environment and can accumulate as plastics. They are not readily biodegradable, and incineration with proper controls is common. Recycling pathways exist but are not universal.