Epoxy or polyepoxide is a thermosetting epoxide polymer that cures (polymerizes and crosslinks) when mixed with a catalyzing agent or "hardener". Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. 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 a 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.
The applications for epoxy based materials are extensive and include coatings, adhesives and composite materials such as those using carbon fiber and fiberglass reinforcements. The chemistry of epoxies and the range of commercially available variations allows cure polymers to be produced with a very broad range of properties. In general, epoxies are known for their excellent adhesion, chemical and heat resistance, good to excellent mechanical properties and very good electrical insulating properties, but almost any property can be modified (for example silver-filled epoxies with good electrical conductivity are available, although epoxies are typically electrically insulating).
Epoxy adhesives are a major part of the class of adhesives called "structural adhesives" or "engineering adhesives" (which also includes polyurethane, acrylic, cyanoacrylate, and other chemistries.) These high performance adhesives are used in the construction of aircraft, automobiles, bicycles, golf clubs, skis, snow boards, and other applications where high strength bonds are required. Epoxy adhesives can be developed that meet almost any application. They are exceptional adhesives for wood, metal, glass, stone, and some plastics. They can be made flexible or rigid, transparent or opaque/colored, fast setting or extremely slow. Epoxy adhesives are almost unmatched in heat and chemical resistance among common adhesives. In general, epoxy adhesives cured with heat will be more heat- and chemical-resistant than when cured at room temperature.
