In chemistry, epoxy or polyepoxide is a thermosetting epoxide polymer that cures (polymerizes and crosslinks) when mixed with a catalyzing agent or "hardener". Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Thermosetting plastics thermosets are Polymer materials that irreversibly cure form An epoxide is a cyclic Ether with only three ring atoms This ring approximately is an Equilateral triangle, i A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. Epichlorohydrin is a reactive Organic compound. It is an Epoxide and an Organochloride. Bisphenol A, commonly abbreviated as BPA, is an Organic compound with two Phenol Functional groups It is a difunctional building block of The first commercial attempts to prepare resins from epichlorohydrin were made in 1927 in the United States. Resin, not to be confused with Rosin, is a Hydrocarbon Secretion of many Plants particularly coniferous trees. Year 1927 ( MCMXXVII) was a Common year starting on Saturday (link will display full calendar of the Gregorian calendar. The United States of America —commonly referred to as the Credit for the first synthesis of bisphenol-A-based epoxy resins is shared by Dr. Pierre Castan of Switzerland and Dr. Switzerland (English pronunciation; Schweiz Swiss German: Schwyz or Schwiiz Suisse Svizzera Svizra officially the Swiss Confederation S. O. Greenlee of the United States in 1936. Year 1936 ( MCMXXXVI) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian calendar. Dr. Castan's work was licensed by Ciba, Ltd. Ciba is a Chemical company based in and near Basel, Switzerland. of Switzerland, which went on to become one of the three major epoxy resin producers worldwide. Ciba's epoxy business was spun off and later sold in the late 1990s and is now the advanced materials business unit of Huntsman Corporation of the United States. Huntsman Corporation is one of the world's largest Chemical companies Dr. Greenlee's work was for the firm of Devoe-Reynolds of the United States. Devoe-Reynolds, which was active in the early days of the epoxy resin industry, was sold to Shell Chemical (now Hexion, formerly Resolution Polymers and others). Royal Dutch Shell plc, commonly known simply as Shell, is a multinational oil company of Dutch and British origins

Industry

As of 2006, the epoxy industry amounts to more than US$5 billion in North America and about US$15 billion world-wide. The United States dollar ( sign: $; code: USD) is the unit of Currency of the United States; it has also been The Chinese market has been growing rapidly, and the market size is more than 30% of the total worldwide market. It is made up of approximately 50–100 manufacturers of basic or commodity epoxy resins and hardeners of which the three largest are Hexion (formerly Resolution Performance Products, formerly Shell Development Company; whose epoxy tradename is "Epon"), The Dow Chemical Company (tradename "D. A commodity is anything for which there is demand but which is supplied without qualitative differentiation across a market The Dow Chemical Company () is an American Multinational corporation headquartered in Midland Michigan. E. R. "), and Huntsman Corporation's Advanced Materials business unit (formerly Vantico, formerly Ciba Specialty Chemical; tradename "Araldite"). In 2007 Huntsman Corporation agreed to merge with Hexion (owned by the Apollo Group)^[1][2]. KUKDO Chemical is one of the largest epoxy manufacturers in Asia, and recently their capacity has been increased up to 210,000 MT/Y (Korea 150,000 MT/Y, China 60,000 MT/Y and will be increased totally 300,000 MT/Y by 2009). Nanya Plastic also has the capacity of over 250,000 MT/Y (Taiwan and China), which is mostly for captive use. There are over 50 smaller epoxy manufacturers primarily producing epoxies only regionally, epoxy hardeners only, specialty epoxies, or epoxy modifiers.

These commodity epoxy manufacturers mentioned above typically do not sell epoxy resins in a form usable to smaller end users, so there is another group of companies that purchase epoxy raw materials from the major producers and then compounds (blends, modifies, or otherwise customizes) epoxy systems from these raw materials. Manufacturing (from Latin manu factura, "making by hand" is the use of tools and labor to make things for use or sale A raw material is something that is acted upon or used by Organisms, or by human labour or Industry, for use as a Building material to create some product These companies are known as "formulators". The majority of the epoxy systems sold are produced by these formulators and they comprise over 60% of the dollar value of the epoxy market. There are hundreds of ways that these formulators can modify epoxies—by adding mineral fillers (talc, silica, alumina, etc. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Talc (derived from the Persian via Arabic talq) is a Mineral composed of Hydrated Magnesium Silicate with The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide ), by adding flexibilizers, viscosity reducers, colorants, thickeners, accelerators, adhesion promoters, etc. Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. A colourant or colorant is something added to something else to cause a change in Colour. Adhesion is the tendency of certain dissimilar molecules to cling together due to Attractive forces. These modifications are made to reduce costs, to improve performance, and to improve processing convenience. As a result a typical formulator sells dozens or even thousands of formulations—each tailored to the requirements of a particular application or market.

The applications for epoxy-based materials are extensive and include coatings, adhesives and composite materials such as those using carbon fiber and fiberglass reinforcements (although polyester, vinyl ester, and other thermosetting resins are also used for glass-reinforced plastic). Glue or adhesive is a compound that adheres or bonds two items together Composite materials (or composites for short are engineered Materials made from two or more constituent materials with significantly different physical or chemical Fiberglass (also called fibreglass and glass fibre see Spelling differences) is material made from extremely fine Fibers of Glass. Polyester is a category of Polymers which contain the Ester Functional group in their main chain Thermosetting plastics thermosets are Polymer materials that irreversibly cure form Resin, not to be confused with Rosin, is a Hydrocarbon Secretion of many Plants particularly coniferous trees. 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. An insulator, also called a Dielectric, is a material that resists the flow of Electric current. Many properties of epoxies can be modified (for example silver-filled epoxies with good electrical conductivity are available, although epoxies are typically electrically insulating). Silver (ˈsɪlvɚ is a Chemical element with the symbol " Ag " (argentum from the Ancient Greek: ἀργήντος - argēntos gen Electrical conductivity or specific conductivity is a measure of a material's ability to conduct an Electric current.

Epoxies find significant use in many applications which are described in following sections.

Paints and coatings

"2 part waterborne epoxy coatings" are used as ambient cure epoxy coatings. These non-HAP, two-part epoxy coatings are developed for heavy duty service on metal substrates and use less energy than heat cured powder coatings. Powder coating is a type of dry coating which is applied as a free-flowing dry powder These systems use a more attractive 4:1 by volume mixing ratio. The coating dries quickly providing a tough, UV resistant, protective coating with excellent ultimate hardness, and good mar and abrasion resistance. They are designed for rapid dry protective coating applications. Ambient cure 2 Part waterborne epoxy coatings provide excellent physical properties in exterior applications. These products have excellent adhesion to various metal substrates. Its low VOC and water clean up makes it a natural choice for factory cast iron, cast steel, cast aluminum applications and reduces exposure and flammability issues associated with solventborne coatings.

Polyester Epoxies are used as powder coatings for washers, driers and other "white goods". Powder coating is a type of dry coating which is applied as a free-flowing dry powder Fusion Bonded Epoxy Powder Coatings (FBE) are extensively used for corrosion protection of steel pipes and fittings used in the oil and gas industry, potable water transmission pipelines (steel), concrete reinforcing rebar, et cetera. Fusion bonded epoxy coating, also known as fusion-bond epoxy powder coating and commonly referred to as FBE coating, is an Epoxy based Powder coating A rebar, or reinforcing bar, is a common Steel bar and is commonly used in Reinforced concrete and reinforced Masonry structures Epoxy coatings are also widely used as primers to improve the adhesion of automotive and marine paints especially on metal surfaces where corrosion (rusting) resistance is important. Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings Metal cans and containers are often coated with epoxy to prevent rusting, especially for foods like tomatoes that are acidic. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are Epoxy resins are also used for high performance and decorative flooring applications especially terrazzo flooring, chip flooring ^[3] and colored aggregate flooring. Terrazzo is a Faux - Marble flooring or Countertopping material ^[4]

Adhesives

Special epoxy is strong enough to withstand the extreme force transferred from a surfboard fin to the fin mount. Surfboards are elongated platforms used in the sport of Surfing. This epoxy is waterproof and capable of curing underwater. The blue-coloured epoxy on the left is still undergoing curing.

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. Glue or adhesive is a compound that adheres or bonds two items together A polyurethane, commonly abbreviated PU, is any Polymer consisting of a chain of organic units joined by urethane links In Organic chemistry, the acryl group is the Functional group with structure H 2 C =CH-C(= O)- it is the Acyl group Cyanoacrylate is the generic name for cyanoacrylate based fast-acting Glues such as ethyl-2-cyanoacrylate (commonly sold under trade names like Superglue and Krazy ) These high-performance adhesives are used in the construction of aircraft, automobiles, bicycles, boats, golf clubs, skis, snow boards, and other applications where high strength bonds are required. Epoxy adhesives can be developed to suit 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 setting. In Optics, transparency (also called pellucidity) is the Material property of allowing Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation especially visible Light. 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 those cured at room temperature.

Some epoxies are cured by exposure to ultraviolet light. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Such epoxies are commonly used in optics, fiber optics, optoelectronics and dentistry. An optical fiber (or fibre) is a Glass or Plastic fiber that carries Light along its length Optoelectronics is the study and application of electronic devices that source detect and control Light, usually considered a sub-field of Photonics. Dentistry' is the "evaluation diagnosis prevention and/or treatment (nonsurgical surgical or related procedures of diseases disorders and/or conditions of the oral cavity

Industrial tooling and composites

Epoxy systems are also used in industrial tooling applications to produce molds, master models, laminates, castings, fixtures, and other industrial production aids. Molding is the process of Manufacturing by shaping pliable raw material using a rigid frame or model called a pattern. A laminate is a material constructed by uniting two or more layers of material together Casting is a manufacturing process by which a liquid material is (usually poured into a mold which This "plastic tooling" replaces metal, wood and other traditional materials and generally improves the efficiency and either lowers the overall cost or shortens the lead-time for many industrial processes. Epoxies are also used in producing fiber reinforced or composite parts. They are more expensive than polyester resins and vinyl ester resins, but generally produce stronger and more temperature resistant composite parts.

Electrical systems and electronics

An epoxy encapsulated hybrid circuit on a printed circuit board. A hybrid integrated circuit, HIC, hybrid microcircuit, or simply hybrid is a miniaturized electronic circuit constructed of individual devices such A printed circuit board, or PCB, is used to mechanically support and electrically connect Electronic components using conductive pathways or traces

Epoxy resin formulations are also important in the electronics industry, and are employed in motors, generators, transformers, switchgear, bushings, and insulators. Epoxy resins are excellent electrical insulators and protect electrical components from short circuiting, dust and moisture. In the electronics industry, epoxy resins are the primary resin used in overmolding integrated circuits, transistors and hybrid circuits, and making printed circuit boards. Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals A hybrid integrated circuit, HIC, hybrid microcircuit, or simply hybrid is a miniaturized electronic circuit constructed of individual devices such A printed circuit board, or PCB, is used to mechanically support and electrically connect Electronic components using conductive pathways or traces The largest volume type of circuit board — an "FR-4 board" — is a sandwich of layers of glass cloth bonded into a composite by an epoxy resin. FR-4, an abbreviation for Flame Retardant 4 is a type of material used for making a Printed circuit board (PCB Epoxy resins are used to bond copper foil to circuit board substrates, and are a component of the solder mask on many circuit boards. Additionally, flexible epoxy resins are used for potting transformers and inductors. By using vacuum impregnation on uncured epoxy, air voids in winding to winding, winding to core and winding to insulator are eliminated. The cured epoxy, as above, is an insulator and a much better conductor of heat than air. Transformer and inductor hot spots are greatly reduced which gives the component a stable and longer life than unpotted product.

Epoxy resins are applied using the technology of resin casting. A resin casting system is a technical installation to process Casting resin for the purpose of filling sealing covering or soaking technical parts especially in the field

Consumer and marine applications

Epoxies are sold in hardware stores, typically as two component kits. They are also sold in boat shops as repair resins for marine applications. Epoxies typically are not used in the outer layer of a boat because they deteriorate by exposure to UV light. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays They are often used during boat repair and assembly, and then over-coated with conventional or two-part polyurethane paint or marine-varnishes that provide UV protection.

There are two main areas of marine use. Because of the better mechanical properties relative to the more common polyester resins, epoxies are used for commercial manufacture of components where a high strength/weight ratio is required. The second area is that their strength, gap filling properties and excellent adhesion to many materials including timber have created a boom in amateur building projects including aircraft and boats.

Normal gelcoat formulated for use with polyester resins and polyester resins does not adhere to epoxy surfaces, though epoxy adheres very well if applied to polyester resin surfaces. A gelcoat is a material used to provide a high quality finish on the visible surface of a fibre-reinforced Composite material. "Flocoat" that is normally used to coat the interior of polyester fibreglass yachts is also compatible with epoxies.

Polyester thermosets typically use a ratio of at least 10:1 of resin to hardener (or "catalyst"), while epoxy materials typically use a lower ratio of between 5:1 and 1:1. Polyester is a category of Polymers which contain the Ester Functional group in their main chain Thermosetting plastics thermosets are Polymer materials that irreversibly cure form A ratio is an expression which compares quantities relative to each other Epoxy materials tend to harden somewhat more gradually, while polyester materials tend to harden quickly.

The classic epoxy reference guide is the Handbook of epoxy resins by Henry Lee and Kris Neville. Kris Ottman Neville better known as Kris Neville is a Californian Science fiction writer Originally issued in 1967, it has been reissued repeatedly and still gives an excellent overview of the technology. Some basic tips are given here:www.epoxy.com/install.htm.

Aerospace applications

In the aerospace industry, epoxy is used as a structural matrix material which is then reinforced by fiber. Typical fiber reinforcements include glass, carbon, Kevlar, and boron. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Kevlar is the registered Trademark for a light strong para-aramid Synthetic fiber, related to other Aramids such as Nomex and Boron (ˈbɔərɒn is a Chemical element with Atomic number 5 and the chemical symbol B. Epoxies are also used as a structural glue. Glue or adhesive is a compound that adheres or bonds two items together Materials like wood, and others that are 'low-tech' are glued with epoxy resin. Wood is hard fibrous lignified structural tissue produced as secondary Xylem in the stems of Woody plants notably trees but also shrubs One example, a homebuilt aircraft, would be the RJ.03 IBIS. This design is based on a classic wooden lattice structured fuselage and a classic wooden spar, internally stiffened with foam and completely covered with plywood. Except for the plywood covering the wings, everything is glued with epoxy resin.

Chemistry

Structure of unmodified epoxy prepolymer. n denotes the number of polymerized subunits and is in the range from 0 to about 25

When epoxies are mixed with the appropriate catalyst, the resulting reaction is exothermic, and the oxygen on the epoxy monomers is "flipped. " This occurs throughout the epoxy, and a matrix with a high stress tolerance is formed, and "glues" the materials together.

Cleanup

When using epoxy resin and hardener, vinegar is an effective and safe solvent to clean up tools, brushes and most surfaces. Vinegar is an acidic liquid processed from the Fermentation of Ethanol in a process that yields its key ingredient Acetic acid (also called ethanoic acid Acetone can also be used, but it is very volatile and flammable. Acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and β-ketopropane) is a colorless mobile flammable Vinegar is much better for cleaning epoxy resin from human skin than acetone. Both liquids will dissolve the resin, but if using acetone, the resin/acetone solution can easily pass through the skin into the bloodstream. This doesn't happen with vinegar. Also vinegar is much cheaper and safer than acetone, since vinegar is not flammable. DME (Dimethoxyethane) is also a good solvent for epoxy resin and hardener that gives off very little vapor. Dimethoxyethane, also known as glyme, monoglyme, dimethyl glycol, ethylene glycol dimethyl ether, dimethyl cellosolve, and White vinegar can even clean up epoxy resin that is beginning to cure/harden. Vinegar is an acidic liquid processed from the Fermentation of Ethanol in a process that yields its key ingredient Acetic acid (also called ethanoic acid However, once cured, vinegar, acetone and DME are no longer effective solvents for dissolving epoxy. A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution.

Health risks

The primary risk associated with epoxy use is sensitization to the hardener, which, over time, can induce an allergic reaction.

Both epichlorohydrin and bisphenol A are suspected endocrine disruptors. Endocrine disruptors (sometimes also referred to as hormonally active agents) are Exogenous substances that act like Hormones in the Endocrine system

According to some reports ^[5] Bisphenol A is linked to the following effects in humans:

• oestrogenic activity;
• alteration of male reproductive organs;
• early puberty induction;
• shortened duration of breast feeding;
• pancreatic cancer

See also

• Thermosetting plastic
• Plastic

References

External links

• Epoxy Resin health hazards (California Department of Health Services)
• The chemistry of epoxide, simple to understand