Epoxies are polymer materials that begin life as liquids and are converted to the solid polymers by a chemical reaction. An epoxy based polymer is mechanically strong, chemically resistant to degradation of the chemical elements in the solid form and highly adhesive during conversion from liquid to solid. There are a wide range of basic epoxy chemicals from which an epoxy system can be formulated.

Physically epoxy systems contain two components, resins and hardeners. The resin component is usually light, sometimes almost clear colored and almost odour free. Hardeners are usually dark and have a characteristic 'ammonia-like' smell. When these two components are brought together and mixed intimately in a prescribed way, they will react chemically and link together irreversibly, and after the chemical reaction has been completed, they will form a rigid plastic material.

Applications of epoxy based materials are extensive and include coatings, adhesives and composite materials like carbon fiber and glass-reinforced plastic (although polyester, vinyl ester, and other thermosetting resins are also used for glass-reinforced plastic). Epoxies are known for their excellent adhesion, chemical and heat resistance, good to excellent mechanical properties and very good electrical insulating properties. Almost any property can be modified.