chemistry and technology of epoxy resins pdf

Chemistry and technology of epoxy resins pdf

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Mitsubishi Chemical Regional Site

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epoxy resins technology handbook pdf

Epoxy Resins: Chemistry and Technology

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Mitsubishi Chemical Regional Site

Epoxy refers to any of the basic components or cured end products of epoxy resins , as well as a colloquial name for the epoxide functional group. 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 usually called mercaptans. 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 favorable mechanical properties and high thermal and chemical resistance. Condensation of epoxides and amines was first reported and patented by Paul Schlack of Germany in Castan's work was licensed by Ciba , Ltd.

Ciba's epoxy business was spun off as Vantico in the late s, which was subsequently sold in and became the Advanced Materials business unit of Huntsman Corporation of the United States.

Most of the 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 may be derived from aliphatic diols , polyols polyether polyols , phenolic compounds or dicarboxylic acids. Phenols can be compounds such as bisphenol A and novolak. Polyols can be compounds such as 1,4-butanediol.

Di- and polyols lead to diglycid polyethers. Dicarboxylic acids such as hexahydrophthalic acid are used for diglycide ester resins. Instead of a hydroxy group, also the nitrogen atom of an amine or amide can be reacted with epichlorohydrin. The other production route for epoxy resins is the conversion of aliphatic or cycloaliphatic alkenes with peracids : [6] [7] In contrast to glycidyl-based epoxy resins, this production of such epoxy monomers does not require an acidic hydrogen atom but an aliphatic double bond.

Bisphenol A-based resins are the most widely commercialised resins but also other bisphenols are analogously reacted with epichlorohydrin, for example Bisphenol F. In this two-stage reaction, epichlorohydrin is first added to bisphenol A bis 3-chlorohydroxy-propoxy bisphenol A is formed , then a bisepoxide is formed in a condensation reaction with a stoichiometric amount of sodium hydroxide.

The chlorine atom is released as sodium chloride NaCl , the hydrogen atom as of water. Instead of bisphenol A, other bisphenols especially bisphenol F or brominated bisphenols e.

Bisphenol F may undergo epoxy resin formation in a similar fashion to bisphenol A. These resins typically have lower viscosity and a higher mean epoxy content per gram than bisphenol A resins, which once cured gives them increased chemical resistance. Important epoxy resins are produced from combining epichlorohydrin and bisphenol A to give bisphenol A diglycidyl ethers.

Increasing the ratio of bisphenol A to epichlorohydrin 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. This route of synthesis is known as the "taffy" process.

This process is known as "advancement". Very high molecular weight polycondensates ca. These resins do however contain hydroxyl groups throughout the backbone, which may also undergo other cross-linking reactions, e.

Epoxy resins are polymeric or semi-polymeric materials or an oligomer , and as such rarely exist as pure substances, since variable chain length results from the polymerisation reaction used to produce them. High purity grades can be produced for certain applications, e. One downside of high purity liquid grades is their tendency to form crystalline solids due to their highly regular structure, which then require melting to enable processing.

An important criterion for epoxy resins is the epoxide group content. This is expressed as the " epoxide equivalent weight ", which is the ratio between the molecular weight of the monomer and the number of epoxide groups. This parameter is used to calculate the mass of co-reactant hardener to use when curing epoxy resins. Epoxies are typically cured with stoichiometric or near-stoichiometric quantities of hardener to achieve the best physical properties.

Novolaks are produced by reacting phenol with methanal formaldehyde. The reaction of epichlorohydrin and novolaks produces novolaks with glycidyl residues , such as epoxyphenol novolak EPN or epoxycresol novolak ECN. These highly viscous to solid resins typically carry 2 to 6 epoxy groups per molecule. By curing, highly cross-linked polymers with high temperature and chemical resistance but low mechanical flexibility are formed due to the high functionality of these resins.

There are two common types of aliphatic epoxy resins: those obtained by epoxidation of double bonds cycloaliphatic epoxides and epoxidized vegetable oils and those formed by reaction with epichlorohydrin glycidyl ethers and esters. Cycloaliphatic epoxides contain one or more aliphatic rings in the molecule on which the oxirane ring is contained e.

They are produced by the reaction of a cyclic alkene with a peracid see above. 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 readily with nucleophiles than bisphenol A-based epoxy resins which have aromatic ether groups. This means that conventional nucleophilic hardeners such as amines are hardly suitable for crosslinking.

Cycloaliphatic epoxides are therefore usually homopolymerized thermally or UV-initiated in an electrophilic or cationic reaction. Due to the 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. Due to their high price, however, their use has so far been limited to such applications. Epoxidized vegetable oils are formed by epoxidation of unsaturated fatty acids by reaction with peracids. In this case, the peracids can also be formed in situ by reacting carboxylic acids with hydrogen peroxide. Compared with LERs liquid epoxy resins they have very low viscosities.

If, however, they are used in larger proportions as reactive diluents , this often leads to reduced chemical and thermal resistance and to poorer mechanical properties of the cured epoxides. Large scale epoxidized vegetable oils such as epoxidized soy and lens oils are used to a large extent as secondary plasticizers and cost stabilizers for PVC. Aliphatic glycidyl epoxy resins of low molar mass 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. Also aliphatic glycidyl epoxy resins usually have a low viscosity compared to aromatic epoxy resins. They are therefore added to other epoxy resins as reactive diluents or as adhesion promoters. Epoxy resins made of long-chain polyols are also added to improve tensile strength and impact strength. A related class is cycloaliphatic epoxy resin, which contains one or more cycloaliphatic rings in the molecule e.

This class also displays lower 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. As aromaticity is not present in these materials as it is in Bisphenol A and F resins, the UV stability is considerably improved.

Halogenated epoxy resins are admixed for special properties, in particular brominated and fluorinated epoxy resins are used. Brominated bisphenol A is used when flame retardant properties are required, such as in some electrical applications e. The tetrabrominated bisphenol A TBBPA, 2,2-bis 3,5-dibromophenyl propane or its diglycidyl ether, 2,2-bis[3,5-dibromo 2,3-epoxypropoxy phenyl]propane, can be added to the epoxy formulation.

The formulation may then be reacted in the same way as pure bisphenol A. Some non-crosslinked epoxy resins with very high molar mass are added to engineering thermoplastics, again to achieve flame retardant properties. Fluorinated epoxy resins have been investigated for some high performance applications , such as the fluorinated diglycidether 5-heptafluoropropyl-1,3-bis[2- 2,3-epoxypropoxy hexafluoropropyl]benzene.

As it has a low surface tension, it is added as a wetting agent surfactant for contact with glass fibres. Its reactivity to hardeners is comparable to that of bisphenol A. When cured, the epoxy resin leads to a thermosetting plastic with high chemical resistance and low water absorption.

However, the commercial use of fluorinated epoxy resins is limited by their high cost and low T g. Epoxy resins diluents are typically formed by glycidylation of aliphatic alcohols or polyols. The resulting materials may be monofunctional e. These resins typically display low viscosity at room temperature mPa. They are rarely used alone, but are rather employed to modify reduce the viscosity of other epoxy resins. Glycidylamine epoxy resins are higher functionality epoxies which are formed when aromatic amines are reacted with epichlorohydrin.

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. There are several dozen chemicals that can be used to cure epoxy, including amines, imidazoles, anhydrides and photosensitive chemicals.

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 or gelation process. Curing may be achieved by reacting an epoxy with itself homopolymerisation or by forming a copolymer with polyfunctional curatives or hardeners.

This curing is what produces the qualities of the substance such as resistance, durability, versatility, and adhesion. In principle, any molecule containing a 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. 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 require 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.

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Epoxy resins have probably provided more interesting chemistry than any other polymer the paint industry uses. The work involves condensing bisphenol A and epichlorohydrin in the presence of small amounts 0. The dye, for example, can be the glycidyl ether of alpha aminoanthroquinone. Coloured products resulted which presumably would provide coatings with intrinsic colour. Of course, this colour could be modified by extrinsic dyes and pigments.

epoxy resins technology handbook pdf

The design of a degradable high-performing thermoset without using organic solvents is critical for the understanding and sustainable development of homogeneous structures with simultaneous reinforcement and toughening functions. Here, we report a novel degradable and recyclable thermoset hyperbranched epoxy resin EFTH- n synthesized from bio-based 2,5-furandicarboxylic acid FDCA. EFTH- n showed excellent performance on common diglycidyl ether of bisphenol-A DGEBA with simultaneous improvements in the impact strength, tensile strength, flexural strength, storage modulus and elongation by up to We concluded that EFTH- n could significantly facilitate the degradation of the cured composites under mild conditions without using organic solvents together with a FDCA recycling yield of If you are not the author of this article and you wish to reproduce material from it in a third party non-RSC publication you must formally request permission using Copyright Clearance Center.

Epoxy refers to any of the basic components or cured end products of epoxy resins , as well as a colloquial name for the epoxide functional group. 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 usually called mercaptans. These co-reactants are often referred to as hardeners or curatives, and the cross-linking reaction is commonly referred to as curing.

Various kinds of compounds are used as curing agents or cross-linking agents according to the particular application. The main types can be roughly classified into the following groups by chemical structure. A Japanese Ministry of Health, Labor, and Welfare toxicity study concluded that bisphenol A liquid epoxy resin and bisphenol F liquid epoxy resin are mutagenic. Therefore, when handling, it is necessary to follow the guidelines provided by the Ministry.

Epoxy Resins: Chemistry and Technology

In some cases, you … XI Epoxy Resins. Epoxy resin is also used to modify several polymers such as polyurethane or unsaturated polyesters to enhance their physical and chemical attributes. Free Download Here pdfsdocuments2 com. Epoxy resins are thermosetting resins, meaning that they do not develop useful properties until they are reacted with suitable cross-linking agents.

It seems that you're in Germany. We have a dedicated site for Germany. Epoxy resins have been commercially available for about 45 years and now have many major industrial applications, especially where technical advantages warrant their somewhat higher costs.

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Coatings update: review articles on epoxy resins

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