Epoxy glues
Introduction
The term epoxy refers to both any of the components and the final (cured) product of the so-called epoxy resins. It is also the colloquial name for the epoxide functional group.[1] Epoxy resins, also called polyepoxides, are a class of reactive polymers and prepolymers, containing epoxide groups.
They can be reacted (cross-link) both with themselves, through catalytic homopolymerization, and with co-reagents including polyfunctional amines, acids, acid anhydrides, phenols, alcohols and thiols. These co-reagents are often called hardeners or curing agents; and the "cross-linking" reaction as "curing".[2] The reaction of polyepoxides with themselves or with polyfunctional hardeners gives rise to thermostable polymers,[3] which usually have good mechanical properties and high chemical and thermal resistance. They have a wide range of applications including metallic coatings, use in electronic/electrical and LED components, insulators in high voltage installations, in paints, in fiber reinforced materials and as structural adhesives.
The most common epoxy resins are the product of a reaction between epichlorohydrin and bisphenol A.
History
The first commercial production attempts took place in 1927 in the United States.
The condensation of epoxides and amines was described and patented by Paul Schlack of Germany in 1934.[4] The merit of the first synthesis of a resin based on bisphenol-a was shared in 1936 by the Swiss Pierre Castan (patented in 1938) and the American S.O. Greenlee (patented 1948).
Castan's work was licensed by the Swiss chemical company Ciba, Ltd., which quickly became one of the top three producers of epoxy resins in the world, marketing them under the name Araldite. Ciba's epoxy business was separated and then sold in the late 1990s and is now an Advanced Materials business unit of Huntsman Corporation of the United States.
Greenlee, working for the small American company Devoe-Reynolds, patented a resin derived from bisphenol-A and epichlorohydrin.[5] Devoe-Reynolds, which was active in the early days of the epoxy resin industry, was sold to Shell Chemical (now Momentive Specialty Chemicals, formerly Hexion, Resolution Polymers and others).