EPOXY RESIN

A Technical Report
Presented to
Prof. Jaime Dilidili
Department of Management
College of Economics, Management and Development Studies
Cavite State University
Indang, Cavite

In partial fulfillment of the requirements in CENG 28
(Materials of Engineering)

ERJHON C. DINGLASAN
October 2015 ABSTRACT Knowledge of the materials has always been necessary for those who design. With today’s stringent demand on quality regarding manufacture, materials and execution, it is often assumed that purchasers, architects and contractors posses the necessary knowledge of that with which they work. This paper described one of the commonly used engineering materials nowadays. Epoxy resin which is routinely used as adhesives, coating encapsulates, casting materials, potting compounds and binders. INTRODUCTION Epoxy resins were first commercialized in 1946 and are widely used in industry as protective coatings and for structural applications, such as laminates and composites, tooling, molding, casting, bonding and adhesives, and others. The ability of the epoxy ring to react with a variety of substrates gives the epoxy resins versatility. Treatment with curing agents gives insoluble and intractable thermoset polymers. Some of the characteristics of epoxy resins are high chemical and corrosion resistance, good mechanical and thermal properties, outstanding adhesion to various substrates, low shrinkage upon cure, good electrical insulating properties, and the ability to be processed under a variety of conditions. Depending on the specific needs for certain physical and mechanical properties, combinations of choices of epoxy resin and curing agents can usually be formulated to meet the market demands. HISTORY Epoxy plastic has its roots far back in history, to be specific, in 1936, when Dr. Pierre Castan in Switzerland succeeds in synthesizing an epoxy resin that he hardened with phthalic acid anhydride. In 1939, Dr. S.O. Greenlee in the USA developed epoxy resins of epichlorohydrin and bisphenol, the type of epoxy we use today. The purpose of development was to find a binding agent for coatings that were resistant to alkali, but it was soon shown that the epoxy had significantly more good properties than this. Today epoxy has its given place in aerospace, electronics and the automotive industry, as well as in foodstuffs, pharmaceuticals, manufacturing, offshore and marine industry. Most people are familiar with the word epoxy and associate it with something that is strong.
EPOXY RESIN Epoxy is a term used to denote both the basic components and the cured end products of epoxy resins, as well as a colloquial name for the epoxide functional group. Epoxy resins, also known as polyepoxides are a class of reactive prepolymers and polymers which contain epoxide groups. Epoxy resins may be reacted (cross-linked) either with themselves through catalytic homopolymerisation, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols and thiols. These co-reactants are often referred to as hardeners or curatives, and the cross-linking reaction is commonly referred to as curing. Reaction of polyepoxides with themselves or with polyfunctional hardeners forms a thermosetting polymer, often with high mechanical properties, temperature and chemical resistance. Epoxy has a wide range of applications, including metal coatings, use in electronics / electrical components, high tension electrical insulators, fiber-reinforced plastic materials and structural adhesives. An epoxy resin is defined as a molecule with more than one epoxy group, which can be hardened into a usable plastic. The epoxy group, which is also called glycidyl group, has through its characteristics appearance given the name epoxy.

What we see is an oxygen atom on the outside of the carbon chain. Epi means “on the outside of” and the second part of the word comes from oxygen. There are two spellings, namely epoxy and epoxy. The first comes from the oxygen bond with the carbon chain being called an oxide. Epoxy resin is manufactured from simple basic chemicals that are readily available.

By varying the relation between bisphenol A and epichlorohydrin, various molecular weights are obtained for the completed epoxy resin. The lowest molecular weight an epoxy resin of the DGEBA type can have 340, but if two elements together can form different molecular weights when they react, the epoxy resin will contain a mixture of epoxy molecules of varying lengths. One therefore does not refer to the epoxy resins’ molecular weight, but rather to their mean molecular weight. Epoxy resin with a mean molecular weight over 700 is called high molecular while mean molecular under 700 is low molecular. Epoxy resins can be allergens, and it is the molecular weight that determines how great the risk. The higher the molecular weight, the lower the probabilities for allergies. Molecular weight of epoxy resin also determines where it can be used for. A low molecular epoxy resin with a mean molecular weight of 380 is fluid at room temperature. It can be handled without solvent additives, which evaporate and therefore used for casting, thick coatings, gap filling glues, etc. while an epoxy with a mean molecular weight of 1000 is solid at room temperature. It must as a rule to dissolve it in organic solvents to be manageable, which limits usage to paints and lacquers.
Common types of Epoxy resin * Bisphenol A epoxy resin
The most common and important class of epoxy resins is formed from reacting epichlorhydrin with bisphenol A to form diglycidyl ethers of bisphenol A. The simplest resin of this class is formed from reacting two moles of epichlorhydrin with one mole of bisphenol A to form the bisphenol A diglycidyl ether (commonly abbreviated to DGEBA or BADGE). DGEBA resins are transparent colourless-to-pale-yellow liquids at room temperature, with viscosity typically in the range of 5-15 Pa.s at 25°C. Industrial grades normally contain some distribution of molecular weight, since pure DGEBA shows a strong tendency to form a crystalline solid upon storage at ambient temperature.

Structure of bisphenol-A diglycidyl ether epoxy resin: n denotes the number of polymerized subunits and is typically in the range from 0 to 25
Increasing the ratio of bisphenol A to epichlorhydrin during manufacture produces higher molecular weight linear polyethers with glycidyl end groups, which are semi-solid to hard crystalline materials at room temperature depending on the molecular weight achieved. As the molecular weight of the resin increases, the epoxide content reduces and the material behaves more and more like a thermoplastic. Very high molecular weight polycondensates (ca. 30 000 – 70 000 g/mol) form a class known as phenoxy resins and contain virtually no epoxide groups (since the terminal epoxy groups are insignificant compared to the total size of the molecule). These resins do however contain hydroxyl groups throughout the backbone, which may also undergo other cross-linking reactions, e.g. with aminoplasts, phenoplasts and isocyanates. * Bisphenol F epoxy resin
Bisphenol F may also undergo epoxidation in a similar fashion to bisphenol A. Compared to DGEBA, bisphenol F epoxy resins have lower viscosity and a higher mean epoxy content per gramme, which (once cured) gives them increased chemical resistance. * Nevolac epoxy resin
Reaction of phenols with formaldehyde and subsequent glycidylation with epichlorhydrin produces epoxidised novolacs, such as epoxy phenol novolacs (EPN) and epoxy cresol novolacs (ECN). These are highly viscous to solid resins with typical mean epoxide functionality of around 2 to 6. The high epoxide functionality of these resins forms a highly crosslinked polymer network displaying high temperature and chemical resistance, but low flexibility.

* Aliphatic epoxy resin
Aliphatic epoxy resins are typically formed by glycidylation of aliphatic alcohols or polyols. The resulting resins may be monofunctional (e.g. dodecanol glycidyl ether), difunctional (butanediol diglycidyl ether), or higher functionality (e.g. trimethylolpropane triglycidyl ether). These resins typically display low viscosity at room temperature (10-200 mPa.s) and are often referred to as reactive diluents. They are rarely used alone, but are rather employed to modify (reduce) the viscosity of other epoxy resins. This has led to the term ‘modified epoxy resin’ to denote those containing viscosity-lowering reactive diluents. A related class is cycloaliphatic epoxy resin, which contains one or more cycloaliphatic rings in the molecule (e.g. 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate). This class also displays low viscosity at room temperature, but offers significantly higher temperature resistance than the aliphatic epoxy diluents. However, reactivity is rather low compared to other classes of epoxy resin, and high temperature curing using suitable accelerators is normally required. * Glycidylamine epoxy resin
Glycidylamine epoxy resins are higher functionality epoxies which are formed when aromatic amines are reacted with epichlorhydrin. Important industrial grades are triglycidyl-p-aminophenol (functionality 3) and N,N,N,N-tetraglycidyl-4,4-methylenebis benzylamine (functionality 4). The resins are low to medium viscosity at room temperature, which makes them easier to process than EPN or ECN resins. This coupled with high reactivity, plus high temperature resistance and mechanical properties of the resulting cured network makes them important materials for aerospace composite applications.

CO-REACTANTS OR HARDENERS
In general, uncured epoxy resins have only poor mechanical, chemical and heat resistance properties. However, good properties are obtained by reacting the linear epoxy resin with suitable curatives to form three-dimensional cross-linked thermoset structures. This process is commonly referred to as curing. Curing of epoxy resins is an exothermic reaction and in some cases produces sufficient heat to cause thermal degradation if not controlled.
Curing may be achieved by reacting an epoxy with itself (homopolymerisation) or by forming a copolymer with polyfunctional curatives or hardeners. In principle, any molecule containing reactive hydrogen may react with the epoxide groups of the epoxy resin. Common classes of hardeners for epoxy resins include amines, acids, acid anhydrides, phenols, alcohols and thiols. Relative reactivity (lowest first) is approximately in the order: phenol < anhydride < aromatic amine < cycloaliphatic amine < aliphatic amine < thiol.
Whilst some epoxy resin/ hardener combinations will cure at ambient temperature, many require heat, with temperatures up to 150°C being common, and up to 200°C for some specialist systems. Insufficient heat during cure will result in a network with incomplete polymerisation, and thus reduced mechanical, chemical and heat resistance. Cure temperature should typically attain the glass transition temperature (Tg) of the fully cured network in order to achieve maximum properties. Temperature is sometimes increased in a step-wise fashion to control the rate of curing and prevent excessive heat build-up from the exothermic reaction.
Hardeners which show only low or limited reactivity at ambient temperature, but which react with epoxy resins at elevated temperature are referred to as latent hardeners. When using latent hardeners, the epoxy resin and hardener may be mixed and stored for some time prior to use, which is advantageous for many industrial processes. Very latent hardeners enable one-component (1K) products to be produced, whereby the resin and hardener are supplied pre-mixed to the end user and only requires heat to initiate curing. One-component products generally have shorter shelf-lives than standard 2-component systems, and products may require cooled storage and transport.
The epoxy curing reaction may be accelerated by addition of small quantities of accelerators. Tertiary amines, carboxylic acids and alcohols (especially phenols) are effective accelerators. Bisphenol A is a highly effective and widely used accelerator, but is now increasingly replaced due to health concerns with this substance.
Most common types of co-reactants or hardeners use for epoxy resins are: Polyamide, Aromatic Amine, Amidoamine, Aliphatic Amine, Cycloaliphatic Amine, and Aliphatic Amine Adduct. * Homopolymerisation
Epoxy resin may 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 homopolymerisation. The resulting network contains only ether bridges, and exhibits high thermal and chemical resistance, but is brittle and often requires elevated temperature to effect curing, so finds only niche applications industrially. Epoxy homopolymerisation is often used when there is a requirement for UV curing, since cationic UV catalysts may be employed (e.g. for UV coatings). * Amines
Polyfunctional primary amines form an important class of epoxy hardeners. Primary amines undergo an addition reaction with the epoxide group to form a hydroxyl group and a secondary amine. The secondary amine can further react with an epoxide to form a tertiary amine and an additional hydroxyl group. Kinetic studies have shown the reactivity of the primary amine to be approximately double that of the secondary amine. Use of a difunctional or polyfunctional amine forms a three-dimensional cross-linked network. Aliphatic, cycloaliphatic and aromatic amines are all employed as epoxy hardeners. Amine type will alter both the processing properties (viscosity, reactivity) and the final properties (mechanical, temperature and heat resistance) of the cured copolymer network. Thus amine structure is normally selected according to the application.
Reactivity is broadly in the order aliphatic amines > cycloaliphatic amines > aromatic amines. Temperature resistance generally increases in the same order, since aromatic amines form much more rigid structures than aliphatic amines. Whilst aromatic amines were once widely used as epoxy resin hardeners due to the excellent end properties they imparted, health concerns with handling these materials means that they have now largely been replaced by safer aliphatic or cycloaliphatic alternatives. * Anhydrides
Epoxy resins may be cured with cyclic anhydrides at elevated temperatures. Reaction occurs only after opening of the anhydride ring, e.g. by secondary hydroxyl groups in the epoxy resin. A possible side reaction may also occur between the epoxide and hydroxyl groups, but this may suppressed by addition of tertiary amines. The low viscosity and high latency of anhydride hardeners makes them suitable for processing systems which require addition of mineral fillers prior to curing, e.g. for high voltage electrical insulators. * Phenols
Polyphenols, such as bisphenol A or novolacs can react with epoxy resins at elevated temperatures (130-180°C), normally in the presence of a catalyst. The resulting material has ether linkages and displays higher chemical and oxidation resistance than typically obtained by curing with amines or anhydrides. Since many novolacs are solids, this class of hardeners is often employed for powder coatings. * Thiols
Also known as mercaptans, thiols contain a hydrogen which reacts very readily with the epoxide group, even at ambient or sub-ambient temperatures. Whilst the resulting network does not typically display high temperature or chemical resistance, the high reactivity of the thiol group makes it useful for applications where heated curing is not possible, or very fast cure is required e.g. for domestic DIY adhesives and chemical rock bolt anchors. Thiols have a characteristic odour, which can be detected in many two-component household adhesives.

GENERAL CHEMICAL AND PHYSICAL CHARACTERISTICS Material | Density
- ρ -
(103 kg/m3) | Tensile Modulus
- E -
(GPa) | Tensile Strength
- σ -
(GPa) | Specific Modulus
- E/ρ - | Specific Strength
- σ/ρ - | Maximum Service Temperature
(oC) | Electrical Insulation Capacity (Ω∙cm) | Epoxy | 1.25 | 3.5 | 0.069 | 2.8 | 0.055 | 80 - 215 | 105 |

Common Types | Viscosity | Flexibility | Chemical Resistance | Bisphenol A | Moderate– High | Moderate | Moderate | Bisphenol F | Moderate | Low–Moderate | Moderate | Phenolic Novolac | Moderate–High | Low | High |

EPOXY PRODUCTION AND INDUSTRY
Most common epoxy resins are produced from a reaction between epichlorohydrin (ECH) and bisphenol-A (BPA), though the latter may be replaced by other raw materials (such as aliphatic glycols, phenol and o-cresol novolacs) to produce specialty resins.
The epoxy resins can be obtained in either liquid or solid states. The two processes are similar. Firstly ECH and BPA are charged into a reactor. A solution of 20-40% caustic soda is added to the reaction vessel as the solution is brought to the boiling point. After the evaporation of unreacted ECH, the two phases are separated by adding an inert solvent such as methylisobutylketone (MIBK). The resin is then washed with water and the solvent is removed by vacuum distillation.The producers will add the specific additivesto create a formula that lend special properties such as flexibility, viscosity, color, adhesiveness, and fastercuring, depending on a particular application.
In order to convert epoxy resins into a hard, infusible, and rigid material, it is necessary to cure the resin with hardener. Epoxy resins can cure at practically any temperature from 5-150oC depending on the choice of curing agent. Primary and secondary amines are widely used to cure epoxy resins.

As of 2006, the epoxy industry amounts to more than US$5 billion in North America and about US$15 billion worldwide. The Chinese market has been growing rapidly, and accounts for 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.
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. 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.), by adding flexibilizers, viscosity reducers, colorants, thickeners, accelerators, adhesion promoters, etc.. 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.
Impacted by the global economic slump, the epoxy market size declined to $15.8 billion in 2009, almost to the level of 2005. In some regional markets it even decreased nearly 20%. The current epoxy market is experiencing positive growth as the global economy revives. With an annual growth rate of 3.5 - 4% the epoxy market is expected to reach $17.7 billion by 2012 and $21.35 billion by 2015. Higher growth rate is foreseen thereafter due to stronger demands from epoxy composite market and epoxy adhesive market. APPLICATIONS * Epoxy Coating Epoxy coatings are durable coatings that can be used for a variety of purposes from strong adhesives to durable paint and coatings for floors and metals. Epoxy coatings are created through the generation of a chemical reaction using an epoxide resin and a polymine hardener. When these two chemicals are combined, a process called “curing” results. This process can take anywhere from several minutes to several hours and turns the liquid epoxy coating in to an extremely strong and durable solid. Because of its ability to create a strong, durable, and chemically resistant substance, epoxy and epoxy coating compounds can be used for a variety of purposes. You can find epoxy coatings used throughout industrial manufacturing plants, in composite materials such as carbon fiber and fiberglass, and in a variety of electrical, automotive, and marine applications. Epoxy materials and epoxy coating compounds can also be used as durable adhesives in a variety of applications. Epoxy Coating Compounds and Paints. One of the most popular epoxy coating uses is the use of epoxy compounds as coatings or paints. Epoxy coatings are popular because they provide a quick drying, tough, and protective coating for metals and other materials. Unlike traditional heat-cured powder coatings, epoxy coatings are quick and easy to apply making them idea for a number of applications. Some of the main epoxy coating uses includes: a) White Goods Coating Applications: An epoxy coating is often used as the coating on washers, driers, and other “white goods” because it is durable and easy to apply. b) Automotive and Marine Applications: An epoxy coating will act as a primer to prevent corrosion and ensure the adhesion of paints on automobiles and boats. c) Steel Corrosion Resistant Coatings: Fusion Bonded Epoxy Powder Coatings are used for corrosion protection in steel pipes and fittings used in the oil and gas industry, water transmission pipelines, and concrete reinforcing rebar. d) Metal Can and Container Coating: Metal cans and containers are often treated with an epoxy coating to prevent rusting especially when used to package acidic foods such as tomatoes. e) Flooring Applications: Epoxy coatings can be used as epoxy floor paint in industrial or commercial applications. Flooring Applications for Epoxy Coatings. When used in flooring applications, an epoxy coating will result in a durable, long lasting flooring solution. Epoxy coatings are used over concrete floors in a variety of commercial and industrial applications such as in manufacturing plants, commercial and retail stores, industrial plants, warehouses, hospitals, showrooms, garages, airplane hangars, and more. Epoxy coatings and floor paints provide a decorative, high gloss finish that is available in a variety of colors and styles. Decorative options that are available when using an epoxy coating on floors include terrazzo flooring, chip flooring, and colored aggregate flooring. An epoxy floor coating offers an easy to clean and chemically resistant flooring solution, which can be applied directly over new or old concrete floors. * Automotive Epoxy resins are widely used in the automotive industry as protective coatings, preserving vehicles and extending their average lifespan. Greater body protection and longer lasting vehicles. Epoxy-based coating technology was introduced in the vehicle production process 30 years ago, providing great advantages in preventing rust and corrosion on vehicles’ body and key metal parts. This technology is known as Waterborne Cathodic Electro Deposition and involves applying a thin anti-corrosive epoxy-based coating as a primer to metal parts. This technique came into widespread use in the 1980s and is used in 90% of cars produced today. After being applied, coatings are cured and covered by a more visually appealing paint which serves both as a top-coat and helps protect the primer from damages by UV light. The role of epoxy resins is to provide superior adhesion to metal and resistance to corrosive agents. Furthermore, epoxy enables the application of a thin, uniform coating directly onto the metal, even in very small spaces and cavities, creating a uniform texture. Better fuel efficiency and lighter structure. In addition to the use in corrosion-resistant paints, epoxies are used in other key applications of the automotive manufacturing industry because of properties such as heat resistance, adhesion and mechanical strength. Some components using epoxies include: a. One-component adhesives b. Electrical insulation coils c. Electrical laminates d. Encapsulation systems for electronics e. Lightweight automotive composite parts Additionally, automotive designers are developing new applications, such as components of electric/hybrid vehicles, parts for suspension systems, drive shafts, various kinds of load-bearing structures of car bodies, etc. Environmental advantages. The use of epoxies in vehicles reduces the weight of the finished part. The benefits of reducing the weight of a car or a truck include lower fuel consumption and operating costs, resulting in fewer emissions as well. Compared to alternative older technologies, epoxies help reduce overall environmental impact. As epoxy-based paint adheres directly to the metal, air emissions and landfill waste are reduced during the production process. In addition, keeping vehicles in service longer conserves energy and raw materials, keeping costs in check and improving the vehicle’s carbon footprint. * Drinking water applications Epoxy is a material with outstanding properties that is used in many important applications where for instance strength, chemical resistance, moisture protection and strong adhesion are key requirements. They are being used in an increasing number of composite pipes and tanks as well as in coatings for traditional steel and concrete products. Thanks to their durability, processing flexibility, resistance to chlorine, microbes and other threats, epoxy resins represent a viable alternative for delivering drinking water. During the post WWII times, the economy boomed and millions of new homes were built. With an expected life time of a water pipe of ca. 50-100 years, more and more of these pipes are suffering corrosion and subsequently are leaking or are releasing metal and other contaminants into the drinking water. The first use of epoxy resins in drinking water applications was in the UK in the 1970s as the commonly used materials of cement mortar and bitumen linings had shown to be ineffective when used under aggressive waters. In addition to the problems arising due to water chemistry, the long times needed to repair pipes with these materials, and the unavailability of water during these periods of several days, also lead to the search for alternative materials. A pipe liner or epoxy coating, applied in-situ without having to dig up the pipe from the ground or open walls to replace the pipe, is a time and cost saving alternative to previously used replacement of drinking water pipes. In addition to the obvious benefits of time and cost, epoxy coatings inside an old pipe also stop pipes from leaking as well as contaminants getting into drinking water from the outside. This in return decreases future deterioration due to oxidation. Also, no galvanic corrosion due to the contact of two different metals can occur. Besides better water quality, also flow and pressure of the water are improved by the smooth surface provided by cured epoxy systems. Corrosion. Factors like chemical composition, pH or temperature of water as well as delivery pressure are factors that can contribute to the corrosion of water pipes. This corrosion can lead to leaching of metals, for instance lead or copper, or other substances from corroded pipes or the environment. Relining creates a barrier between the pipe and the water, thereby preventing these negative interactions and also eliminating galvanic corrosion that results from the joining of dissimilar metals. A classical material for this kind of relining is cement mortar. Unfortunately analysis has shown that many of these cement mortar linings have failed and cause deterioration in water quality. Epoxy linings provide an excellent barrier against contamination, i.e. they prevent that substances from the pipe enter the water. The German UBA (Umwelt Bundesamt) states that pipes (any material) are supposed to have a life time of 50-100 years. The use of epoxy resins for pipe line coatings has only started in the 1970s. US field research has demonstrated that epoxy was a safe and durable material with an estimated life up to 60 years. Economy. As clean, safe drinking water is one of the world’s most important and valued assets, billions are spent each year in order to repair the damage to water pipes that occurs due to corrosion over time. Because pipes are buried within the walls and floors of a building, or in the case of exterior pipes, beneath streets and sidewalks, it can be less costly to re-line these already existing pipes than it is to tear them out, install new pipes and repair the damage done to their surrounding by this repair work. Especially interrupting traffic in heavily populated areas leads to additional costs due to loss of work time and delayed deliveries. This can easily avoided by using epoxy repair systems. In addition, the smooth surface of polymeric linings results in a better flow capacity and thus lower energy cost for water transport. Health. The releases of substances from corroded pipes sometimes can exceed the concentration limits set by the regulators but even if they do not exceed the legislatory limits, they will likely affect the odor, taste and visual appearance of the water and thus render it unsuitable for consumption in the eyes of the consumer. The smoother surface of epoxy linings also generally results in less ability for biofilm growth to occur. Sometimes epoxy resins are reported in the press to release substances into drinking water. In the cases where these allegations could be verified, the reason for the poor performance was either improper installation of the product or an incorrect use of the epoxy system. Epoxy resins are a high performance, specialist material that should only be applied by experts who ensure that the polymer can function at its peak performance. Assessments from the European Food Safety Authority concluded there is no health risk from current uses of BPA, including in food and other applications. Any regulatory action substituting epoxies with substances whose effects on human health and the environment have been subject to less research than epoxies would be driven by reasons other than scientific research and higher food and consumer safety. * Food packaging Epoxy-based resins are key to food and beverage containers’ long shelf life. Long-lasting, highly protected foods. Since the 1950s, epoxies have been used in the internal coating of cans to endure a long shelf life for canned goods, preserving them for up to five years. Their use benefits both consumers, who can store food for long periods after purchase, and producers, who can export local, seasonal food all year-round, using lightweight and affordable packaging while preserving taste, texture and color. Canned products also contribute to improving food security, of particular importance in countries where seasonal food production can vary considerably from year to year. Cans are hermetically sealed, keeping out bacteria and insects, as well as preventing deterioration due to oxidation. Non-transparent cans halt the effect of light and UV rays, critical in tropical and sub-Saharan countries. Epoxy-based resins provide another advantage: creating a protective layer separating foods and drinks from the metal used to make the cans. Without epoxies, the metal could be corroded and bacteria could penetrate the cans, harming the safety of their contents, but also their freshness, nutritional properties and organoleptic properties such taste and smell. Glass packaging also relies on epoxy resins to protect lids from corrosion in bottles and jars, in order to comply with the European Union tight regulation on food packaging. High-engineering processes to deliver greatest safety. What may appear as simple food containers are actually advanced devices whose engineering precision has been likened to the one needed for the production of aircraft wings and space vehicles. Food cans can work as pressure vessels filled with raw food which is then processed and cooked. A robust internal epoxy coating allows for completely safe sterilization at high temperatures and an airtight seal. In general, beer and other beverages undergo a 20-30 minutes cycle at about 65°C. Foods are often cooked at a minimum of 120°C under pressure for up to 90 minutes. Epoxies are also able to withstand the numerous shape-shifting processes withstood by cans. Despite the enormous pressure, cans will not break, crack or lose metallic adherence during this processes and later, while being transported, consumed or accidentally dropped or dented. The most significant technical achievement is perhaps the versatility of the coating. It works for foods with differing corrosive qualities, while maintaining low production costs. For example, without epoxy internal coating, peas and beans would interact with the metallic surface of a can and blacken it, while tomato concentrate would make it red. Krauts or pickles might weaken a can because they contain high levels of salt and acidity levels. Scientists have developed specific safety packaging tests, often lasting several years, which evaluate the cans’ performance through the course of time. At the same time, they have continued refining the production process to ensure cans remain lightweight, produced at high speed and at low cost. Cans must also have minimal environmental impact and should be easily recyclable. According to the North American Packaging Alliance, frozen products require about 70% more energy than metal packaged foods.[3] Cans are very lightweight, resulting into fewer CO2 emissions during their transportation when compared to heavier materials (such as for example glass). Metal cans and glass containers are 100% recyclable, without losing strength or quality. Overall, epoxy-based coatings require a complex production process which delivers significant performance and safety advantages, not to mention their affordability. The chemistry involved in the production of epoxies is no different from the one used to produce epoxies destined to other uses. It involves a reaction between two substances: epichlorohydrin and Bisphenol A (BPA). The latter is later found in minimal traces in the resin which is finally used to produce the coating and is further reduced during the curing process. For more information, visit the European information Centre on Bisphenol A or the BPA Coalition. Protecting food, drinks and its manufacturing machines. Epoxies are also used in industrial food processing equipment. Thanks to their high degree of protection, they can protect metal coverings of containers, pipelines and storage tanks in food processing plants for years, even if used sporadically. This is particularly useful in the case of foods which would absorb and chemically alter metal coverings. Epoxy coatings also help keeping the metal used in food packaging lubricated when being processed in the production line, hence preventing damage to the industrial machinery. Without epoxies, the high-speed production process – which can turn out hundreds of cans per minute – would wear down the production line more rapidly. * Sports Epoxies play a key role in improving the performance of sports and leisure equipment for both amateurs and professionals. Epoxies are being used to produce tennis rackets, skis, golf equipment and hockey sticks, which have become lighter, stronger, more reliable and more resistant to fatigue. Other sports use equipment and gear coated with epoxy resins, such as fishing rods and poles, kayaks, jumping poles, bicycles, archery bows, arrows, etc. In addition, epoxies play a key role in the maritime industry, providing coatings for small and large boats used in a variety of water sports. * Energy Epoxy resins are used both as composites and coatings in the production, transformation and distribution of various types of renewable and non-renewable energy. Key component of wind turbine blades. In the wind sector, composites of epoxy resins and reinforcing fibers have become a standard component of large-sized windmill rotor blades and are also used in smart grids and turbine insulators. Epoxies are used to coat steel and concrete towers of windmills, as well as to impregnate the concrete or steel itself. Wind turbine poles in the North Sea are coated with epoxy resins to protect the structure from salt water corrosion. Finally, materials created with epoxy resins are an indispensable component in offshore, wind energy farms due to their durability and low brittleness, lightweight and high mechanical strength. Wind turbines have grown larger and taller over the last 30 years thanks in part to the increased use of epoxy resins. Epoxies improve the strength-to-weight ratio of turbines’ structure, allowing the manufacture of longer blades which would be more difficult to produce otherwise. * Electronics IT & electronics are a sector where the number of applications of epoxy resins has been increasing sharply in the past few years. In light of their properties as electric insulators, epoxies are a vital component in internal circuits, transistors and printed circuit boards, LED's, solar panels and many other devices. Without epoxies, essential everyday items such as smart phones or modern medical equipment like MRI scans would not exist. Epoxies are easy to use thanks to their several formulations and variable liquid or solid state. Additional advantages include the absence of volatile organic compounds, not needing to sag the coating to make it thicker, less hazardous waste and a wide range of specialty effects further strengthened by the development of new materials and technologies. Greater and safer energy supply. Epoxy resins contribute to increase the reliability and efficiency of energy supply by lowering the costs of electrical transmission and distribution systems. Their properties are particularly useful for products working at high voltage levels, providing greater operational flexibility and durability. The use of epoxy resins brings benefits to end users and energy-intensive businesses alike, many of them being key economic drivers such as for example the manufacturing, distribution or logistics business. EPOXIES—COMMON PROBLEMS AND MOST PROBABLE CAUSES HEALTH
The primary risk associated with epoxy use is often related to the hardener component and not to the epoxy resin itself. Amine hardeners in particular are generally corrosive, but may also be classed toxic and/or carncinogenic/ mutagenic. Aromatic amines present a particular health hazard (most are known or suspected carcinogens), but their use is now restricted to specific industrial applications, and safer aliphatic or cycloaliphatic amines are commonly employed.
Liquid epoxy resins in their uncured state are mostly classed as irritant to the eyes and skin, as well as toxic to aquatic organisms. Solid epoxy resins are generally safer than liquid epoxy resins, and many are classified non-hazardous materials. One particular risk associated with epoxy resins is sensitization. The risk has been shown to be more pronounced in epoxy resins containing low molecular weight epoxy diluents. Exposure to epoxy resins can, over time, induce an allergic reaction. Sensitization generally occurs due to repeated exposure (e.g. through poor working hygiene and/or lack of protective equipment) over a long period of time. Allergic reaction sometimes occurs at a time which is delayed several days from the exposure. Allergic reaction is often visible in the form of dermatitis, particularly in areas where the exposure has been highest (commonly hands and forearms). Epoxy use is a main source of occupational asthma among users of plastics. Bisphenol A, which is used to manufacture a common class of epoxy resins, is a known endocrine disruptor. CONCLUSION In this topic, description, conditions, application, workability other factors about epoxy resin is reviewed. poxy resin has been used in a wide range of fields, such as paints, electricity, civil engineering, and bonds. This is because epoxy resin has excellent bonding property. But to maximize more its workability, epoxy resin is needed to convert into epoxy plastic. To make this possible a reaction with a suitable substance is required. Such in this context is called hardener. After reinforcing, epoxy resin will have excellent bonding property, and also after curing, it has excellent properties on mechanical strength, chemical resistance, and electrical insulation. Though epoxy resin is very useful and helpful in many ways, there still number of publications that outline environmental, safety and health concern related to the use of epoxy composite materials. That is why; there is still a need of proper and safely handling of this material and further study to make it more safe to use. REFERENCES
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