Epoxy, also known as polyepoxide, is a polymer used to create protective coatings, fillers, and scratch-resistant adhesive products for a variety of applications. It is composed of a liquid epoxy resin and a chemical hardener that cures the resin in hardened plastic. Epoxy resin is viscous when in liquid form, cures quickly and adheres to a wide range of substrate materials including wood, metal, glass, concrete and stone. In its most basic form, epoxy is composed of a liquid epoxy resin and a chemical hardener that cures the resin in hardened plastic. The epoxide functional group is also collectively referred to as epoxy.
Epoxy resins are thermosetting polymers with unique mechanical and strength properties. They are the result of a chemical reaction called “curing”, which involves epoxides and other chemicals more commonly known as “hardeners” or curing agents. Various substances can be used as hardeners, including polyamines, aminoamides or phenolic compounds. Epoxy is an organic compound formed by carbon chains linked to other elements such as hydrogen, oxygen or nitrogen. This bond occurs through a covalent bond, in which the elements share a pair of electrons to stay together.
Epoxy resins are formed from a long chain molecular structure similar to vinyl ester with reactive sites at each end. However, in epoxy resin, epoxy groups instead of ester groups form these reactive sites. The absence of ester groups means that the epoxy resin has a particularly good water resistance.The epoxy molecule also contains two groups of rings in its center that are better able to absorb mechanical and thermal stresses than linear groups and therefore give the epoxy resin very good stiffness, toughness and heat resistance properties. Once hardened, epoxy is extremely strong, dimensionally stable and resistant to chemicals. Epoxy reactions offer advantages such as fast curing, which is often necessary for rapid polymer repair.
Although casting and coating epoxies exhibit similar characteristics, it is important to select the epoxy resin that best suits the material and application. However, if used in higher proportions as reactive diluents, this often leads to reduced chemical and thermal resistance and poorer mechanical properties of cured epoxides. In general, primary and secondary alcohols can be produced, since, in theory, both carbons of the epoxide ring are likely to react with the nucleophile or electrophile. Also known as mercaptans, thiols contain a sulfur that reacts very easily with the epoxide group, even at room temperature or below room temperature. Glycidylamine epoxy resins are higher functional epoxies that are formed when aromatic amines are reacted with epichlorohydrin. Epoxies are used in a variety of industrial and consumer applications due to their durability, strong adhesion, chemical resistance and other specialized properties.
Workers may be exposed to uncured epoxy resins if they are not adequately protected or are not handling epoxy resins with the right tools. One of the best examples was a system of using solvent-free epoxies for the priming of ships during construction; this used a spray system without hot air with premix on the head. The reaction of polyepoxides with themselves or with polyfunctional hardeners forms a thermosetting polymer, often with favorable mechanical properties and high thermal and chemical resistance. Large-scale epoxidized vegetable oils such as soybean oils and epoxidized lenses are largely used as secondary plasticizers and cost stabilizers for PVC. Cycloaliphatic epoxides contain one or more aliphatic rings in the molecule in which the oxirane ring is contained (e.g.). Epoxy thermosets are reactions between an epoxy resin, a small molecule or prepolymer that is functionalized with epoxy end groups, and a hardener or crosslinking agent. Because of their ability to adhere to a wide variety of materials, their high strength, their resistance to chemicals and the environment, and their ability to resist creep under sustained load; epoxies are the most widely used structural adhesive.