Epoxy

Epoxy or polyepoxide is a thermoset polymer most widely used as an adhesive and with fiber-reinforced composites, such as carbon fiber and fiberglass containing shells, but is also frequently molded and used as a coating.

It is composed of a resin (epoxide) and a hardener (polyamine).

Technical Details
Epoxy is a copolymer, formed by two different chemicals, a resin (epoxide) and a hardener (polyamine). The resin is a group of short-chain polymers terminated on the end by an epoxide group. This is typically done with a reaction of epichlorohydrin ($$C_3H_5ClO$$) and bisphenol-A ($$C_15H_16O_2$$), however, bisphenol-A can be substituted for many other diols, frequently to replace the chemical with one that is not an endocrine disruptor. The hardener consist of polyamine monomers such as Triethylenetetramine (TETA, $$C_6H_18N_4$$). When mixed, the amine groups combine with the epoxide group to form a covalent bond in a hardening process referred to as "curing".

Synthesis
Epoxies are formed through the combination of a epoxy resin and polyamine hardener, after which the chemicals begin curing and hardening. Depending on which compounds are used, the end product can vary widely with a large range of physical properties. As such, curing time can also vary widely. Many epoxies also contain various additives to further alter properties. For instance, in industrial and outdoors applications, epoxies tend to be combined with a UV resistant additive.

Epoxy is normally used as a strong adhesive, coating, and reinforcement for fiber-reinforced composites such as fiberglass shells, although it can also be used for casting.

Epoxy composition can vary widely, so working with it can vary widely. adhesive epoxies are good for adhering most materials to each other, although specially formulated epoxies are required for some applications, such as bonding to silicone rubber. Most epoxy can be cut, but many to not take well to sanding or machining, although some stiffer, more structurally stable epoxies respond well to these methods. Many epoxies can be molded well and easily due to not hardening until mixed, and reasonable working times. However, epoxy will also bond strongly to many types of molds, requiring a specially formulated mold release, or certain, largely non-reactive mold materials such as silicon rubber.

Reference

 * http://en.wikipedia.org/wiki/Epoxy
 * Synthetic Polymer Chemistry
 * Epoxy Polymers