One of the most common uses of epoxy resin is for adhesive purposes. This is because epoxy's strong properties allow for structural and engineering adhesives. Commonly, epoxy resin is used in the construction of vehicles, snowboards, airplanes and bicycles. Epoxy resin is usually a two-part adhesive that can be used for repairs.
Often used to repair broken objects or to create a sealant. The adhesive will harden and form a strong bond once mixed. This makes epoxy resin ideal for repairing items such as vases, figurines, ornaments and more. Epoxy resin is a versatile adhesive that can be used for various repairs.
It is easy to use and hardens quickly, forming a strong bond. Whether you're repairing a broken object or creating a sealant, epoxy resin is an ideal choice for the job. Epoxy resins are used in art to design paints and jewelry, produce varnishes and create castings. Epoxies can be used to finish drawings, photos and images and protect art from ultraviolet light.
Epoxy resin casting allows artists to embed natural materials such as flowers, plants and stones into the foundry. Their strength and durability allow them to withstand sculpting and carving at high and low temperatures. 3.Epoxy resin has come a long way since its original formula. Nowadays, you can buy epoxy adhesives at hardware stores everywhere, and epoxy resin is now widely used for floor coverings and as a binder for countertops.
Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers that contain epoxy groups. The epoxy functional group is also collectively referred to as epoxy. The IUPAC name for an epoxide group is oxirane.
Epoxy resins can be reacted (crosslinked) with themselves through catalytic homopolymerization, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols and thiols (commonly referred to as mercaptans). These coreactants are often referred to as hardeners or curing agents, and the cross-linking reaction is commonly referred to as curing. 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. Epoxy has a wide range of applications, including metal coatings, composites, use in electronics, electrical components (e.g.
For on-board chips), LEDs, high-voltage electrical insulators, brush making, fiber-reinforced plastics and adhesives for structural and other purposes. Health risks associated with exposure to epoxy resin compounds include contact dermatitis and allergic reactions, as well as respiratory problems from breathing steam and sanding dust, especially when they are not fully cured. Most commercially used epoxy monomers are produced by the reaction of a compound with acidic hydroxy groups and epichlorohydrin. First, a hydroxy group reacts in a coupling reaction with epichlorohydrin, followed by dehydrohalogenation.
Epoxy resins produced from such epoxy monomers are called glycidyl based epoxy resins. The hydroxy group can be derived from aliphatic diols, polyols (polyether polyols), phenolic compounds, or dicarboxylic acids. Phenols can be compounds such as bisphenol A and novolac. Polyols can be compounds such as 1,4-butanediol.
Di- and polyols lead to glycidyl ethers. Dicarboxylic acids, such as hexahydrophthalic acid, are used for diglycide ester resins. Instead of a hydroxy group, the nitrogen atom of an amine or amide can also be reacted with epichlorohydrin. The epoxide group is also sometimes referred to as an oxirane group.
The most common epoxy resins are based on the reaction of epichlorohydrin (ECH) with bisphenol A, resulting in a different chemical known as diglycidyl ether of bisphenol A (commonly known as BADGE or DGEBA). Resins based on bisphenol A are the most widely marketed resins, but other bisphenols are likewise reacted with epichlorohydrin, for example, bisphenol F. In this two-step reaction, epichlorohydrin is first added to bisphenol A (bis (3-chloro-2-hydroxypropoxy), bisphenol A is formed), then a biepoxide is formed in a condensation reaction with a stoichiometric amount of sodium hydroxide. The chlorine atom is released as sodium chloride (NaCl) and the hydrogen atom as water.
A product comprising a few repeating units (n%3D 1 a) is a transparent, viscous liquid; this is called a liquid epoxy resin. A product comprising more repeating units (n%3D 2 to 30) is at room temperature a colorless solid, which is correspondingly referred to as a solid epoxy resin. Instead of bisphenol A, other bisphenols (especially bisphenol F) or brominated bisphenols (e.g. Tetrabromobisphenol (A) can be used for such epoxidation and prepolymerization.
Bisphenol F can undergo epoxy resin formation in a manner similar to that of bisphenol A. These resins typically have a lower viscosity and a higher average epoxy content per gram than bisphenol A resins, which (once cured) gives them greater chemical resistance. Important epoxy resins are produced from the combination of epichlorohydrin and bisphenol A to give diglycidyl ethers of bisphenol A. An important criterion for epoxy resins is the epoxy value, which is related to the content of the epoxy group.
This is expressed as the epoxide equivalent weight, which is the ratio between the molecular weight of Rorar and the number of epoxide groups. This parameter is used to calculate the mass of coreactant (hardener) to be used when curing epoxy resins. Epoxies are typically cured with stoichiometric or near stoichiometric amounts of hardener to achieve the best physical properties. Novolacs are produced by reacting phenol with methanal (formaldehyde).
The reaction of epichlorohydrin and novolacs produces novolacs with glycidyl residues, such as epoxyphenol novolac (EPN) or epoxycresol novolac (ECN). These highly viscous to solid resins typically carry 2 to 6 epoxy groups per molecule. By curing, highly crosslinked polymers are formed with high temperature and chemical resistance but low mechanical flexibility due to the high functionality and, therefore, the high crosslink density of these resins. Cycloaliphatic epoxides contain one or more aliphatic rings in the molecule in which the oxirane ring is contained (e.g.
They are produced by the reaction of a cyclic alkene with a peracid (see above). Cycloaliphatic epoxides are characterized by their aliphatic structure, high oxirane content and absence of chlorine, which results in low viscosity and (once cured) good weather resistance, low dielectric constants and high Tg. However, aliphatic epoxy resins polymerize very slowly at room temperature, so higher temperatures and suitable accelerators are usually required. Because aliphatic epoxies have a lower electron density than aromatics, cycloaliphatic epoxies react less easily with nucleophiles than epoxy resins based on bisphenol A (which have aromatic ether groups).
This means that conventional nucleophilic hardeners, such as amines, are hardly suitable for crosslinking. Therefore, cycloaliphatic epoxides are typically thermally homopolymerized or UV-initiated in an electrophilic or cationic reaction. Due to low dielectric constants and the absence of chlorine, cycloaliphatic epoxides are often used to encapsulate electronic systems, such as microchips or LEDs. They are also used for radiation-cured paints and varnishes.
However, due to its high price, its use has so far been limited to this type of application. Low molar mass aliphatic epoxy glycidyl resins (mono-, bi- or polyfunctional) are formed by the reaction of epichlorohydrin with aliphatic alcohols or polyols (glycidyl ethers are formed) or with aliphatic carboxylic acids (glycidyl esters are formed). The reaction is carried out in the presence of a base such as sodium hydroxide, analogous to the formation of bisphenol A-diglycidyl ether. In addition, aliphatic glycidyl epoxy resins typically have a low viscosity compared to aromatic epoxy resins.
Therefore, they are added to other epoxy resins as reactive diluents or as adhesion promoters. Epoxy resins made of polyols (long chain) are also added to improve tensile strength and impact resistance. A related class is cycloaliphatic epoxy resin, which contains one or more cycloaliphatic rings in the molecule (e.g. This class also shows a lower viscosity at room temperature, but offers significantly higher temperature resistance than aliphatic epoxy diluents.
However, the reactivity is quite low compared to other classes of epoxy resin, and high temperature curing using suitable accelerators is usually required. Because aromaticity is not present in these materials as it is in bisphenol A and F resins, UV stability is greatly improved. Halogenated epoxy resins are blended to obtain special properties, in particular brominated and fluorinated epoxy resins are used. Glycidylamine epoxy resins are higher functional epoxies that form when aromatic amines are reacted with epichlorohydrin.
Important industrial grades are triglycidyl-p-aminophenol (functionality) and N, N, N′, N′-tetraglycidyl-bis- (4-aminophenyl) -methane (functionality). Resins are low to medium viscosity at room temperature, making them easier to process than EPN or ECN resins. This, together with the high reactivity, plus the high temperature resistance and mechanical properties of the resulting cured network, makes them important materials for aerospace composite applications. Hardeners that show only low or limited reactivity at room temperature, but which react with epoxy resins at elevated temperature are called latent hardeners.
When using latent hardeners, the epoxy resin and hardener can be mixed and stored for some time before use, which is advantageous for many industrial processes. Highly latent hardeners allow one-component (1K) products to be produced, so the resin and hardener are supplied premixed to the end user and require only heat to initiate curing. One-component products generally have a shorter lifespan than standard 2-component systems, and products may require refrigerated storage and transportation. The epoxy resin can be reacted with itself in the presence of an anionic catalyst (a Lewis base such as tertiary amines or imidazoles) or a cationic catalyst (a Lewis acid such as a boron trifluoride complex) to form a cured network.
This process is known as catalytic homopolymerization. The resulting network contains only ether bridges and exhibits high thermal and chemical resistance, but is brittle and often requires an elevated temperature for the curing process, so it finds only niche applications at the industrial level. Epoxy homopolymerization is often used where there is a requirement for UV curing, since cationic UV catalysts (e.g. Polyphenols, such as bisphenol A or novolacs, can react with epoxy resins at elevated temperatures (130—180°C, 266—356 °F), usually in the presence of a catalyst.
The resulting material has ether bonds and shows greater chemical and oxidation resistance than that typically obtained by curing with amines or anhydrides. Because many novolacs are solid, this class of hardener is often used for powder coatings. Also known as mercaptans, thiols contain a sulfur that reacts very easily with the epoxide group, even at or below ambient temperature. While the resulting network typically does not exhibit high temperature or chemical resistance, the high reactivity of the thiol group makes it useful for applications where hot curing is not possible, or very fast curing is required, e.g.
For DIY household adhesives and chemical rock bolt anchors. Thiols have a characteristic odor, which can be detected in many two-component household adhesives. As with other classes of thermosetting polymeric materials, mixing different grades of epoxy resin, as well as the use of additives, plasticizers, or fillers is common to achieve the desired processing or final properties, or to reduce cost. The use of blends, additives and fillers is often referred to as formulation.
Two-component epoxy coatings were developed for heavy duty on metal substrates and use less energy than heat-cured powder coatings. These systems provide a tough protective coating with excellent hardness. One-part epoxy coatings are formulated as an emulsion in water and can be cleaned without solvents. Polyester epoxies are used as powder coatings for washing machines, dryers and other white goods.
Fusion Bonded Epoxy (FBE) powder coatings are widely used for corrosion protection of steel pipes and fittings used in the oil and gas industry, drinking water (steel) transmission pipelines, and concrete rebar. Epoxy coatings are also widely used as primers to improve the adhesion of automotive and marine paints, especially on metal surfaces where resistance to corrosion (oxidation) is important. Metal cans and containers are often epoxy coated to prevent rust, especially for foods such as tomatoes that are acidic. Epoxy resins are also used for decorative flooring applications, such as terrazzo floors, chip floors, and colored aggregate floors.
One of the best examples was a system of using solvent-free epoxies to prime ships during construction, this used a spray system without hot air with premix on the head. This avoided the problem of solvent retention under the film, which caused adhesion problems later on. Some epoxies are cured by exposure to ultraviolet light. Such epoxies are commonly used in optics, fiber optics, and optoelectronics.
Epoxy systems are used in industrial tool applications to produce molds, master models, laminates, castings, fixtures and other industrial production aids. This plastic tool replaces traditional metal, wood and other materials and generally improves efficiency and reduces total cost or shortens lead time for many industrial processes. Epoxies are also used in the production of composite or fiber-reinforced parts. They are more expensive than polyester resins and vinyl ester resins, but generally produce stronger and more temperature-resistant thermosetting polymer matrix composite parts.
Flexible epoxy resins are used to encapsulate transformers and inductors. By using vacuum impregnation on uncured epoxy, wind-to-coil, wind-to-core, and wind-to-insulation air voids are eliminated. Cured epoxy is a much better electrical insulator and conductor of heat than air. Transformer and inductor hot spots are significantly reduced, giving the component a longer and more stable service life than the product without packaging.
Epoxy resins are applied using resin dispensing technology. Epoxies are sold in hardware stores, usually as a separate package containing resin and hardener, which must be mixed immediately before use. They are also sold in boat stores as repair resins for marine applications. Epoxies are not normally used in the outer shell of a ship because they deteriorate from exposure to ultraviolet light.
They are often used during boat repair and assembly, and then coated with conventional or two-component polyurethane paint or marine varnishes that provide UV protection. Normal gelcoat formulated for use with polyester resins and vinylester resins does not adhere to epoxy surfaces, although epoxy adheres very well if applied to polyester resin surfaces. Flocoat, which is normally used to coat the interior of polyester fiberglass yachts, is also compatible with epoxies. Although it is common to associate polyester resins and epoxy resins, their properties are sufficiently different that they are properly treated as separate materials.
Polyester resins are typically of low strength unless used with a reinforcing material such as fiberglass, are relatively brittle unless reinforced, and have low adhesion. Epoxies, on the other hand, are inherently strong, somewhat flexible, and have excellent adhesion. However, polyester resins are much cheaper. “By contrast, polyester resins are generally available in a “” promoted "” form, so that the progress of pre-blended resins from liquid to solid is already underway, albeit very slowly.”.
The only variable available to the user is to change the speed of this process using a catalyst, often methyl ethyl ketone peroxide (MEKP), which is very toxic. The presence of the catalyst in the final product actually detracts from desirable properties, so small amounts of catalyst are preferable, provided that curing proceeds at an acceptable rate. Thus, the curing speed of polyesters can be controlled by the amount and type of catalyst, as well as by temperature. These basic epoxy manufacturers mentioned above generally do not sell epoxy resins in a form usable for smaller end users, so there is another group of companies that purchase epoxy raw materials from major producers and then composes (mixes, modifies, or otherwise customizes) the epoxy systems of these raw materials.
These companies are known as formulators. Most epoxy systems sold are produced by these formulators and represent more than 60% of the dollar value of the epoxy market. There are hundreds of ways in which these formulators can modify epoxies by adding mineral fillers (talc, silica, alumina, etc.). These modifications are made to reduce costs, improve performance, and 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. Raw materials for epoxy resin production are largely petroleum-derived, although some plant-derived sources are now commercially available (for example,. Plant-derived glycerol (used to make epichlorohydrin). Curing with phenolic compounds to make drum liners, cure esters with amine resins, and pre-cure epoxies with amino resins to make tough topcoats.
China is the world's leading producer and consumer, consuming almost 35% of global resin production. Wessex Resins and Adhesives has been developing and manufacturing high quality epoxy products since 1981.However, if used in greater proportions as reactive diluents, this often leads to lower chemical and thermal resistance and poorer mechanical properties of cured epoxides. Like the other projects mentioned above, making the resin jewelry simply involves mixing the epoxy resin, having a series of molds to use, and experimenting with paint, glitter and other fun pieces in the molds with the resin. When resin (often called “steel”) is mixed with the hardener, the result will transform, over the course of 24 hours, from a thick liquid into a putty and, finally, into a fully cured and hardened material.
Epoxy resin diluents are typically formed by glycidylation of aliphatic alcohols or polyols and also aromatic alcohols. Research is underway to investigate the use of epoxies and other recycled plastics in mortars to improve properties and recycle waste. In the field of fiber-reinforced polymers, or plastics, epoxy is used as a resin matrix to efficiently hold the fiber in place. Most epoxies are waterproof when hardened, but some are specifically designed so that they can cure even when exposed to water.