Epoxy hardeners

The basic chemical reaction between an epoxy and a primary amine can be represented by  

A common modification which is performed commercially to selectively improve the performance is to react a glycidyl ether resin with an excess of amine groups to produce a resinous amine adduct hardener. These have advantages over unmodified versions in that they result in more convenient mixing ratios, are less dangerous to handle and can exhibit reduced moisture sensitivity. 

Cycloaliphatic amines. These can give good cures under adverse conditions of low temperature and high humidity and as such form 

Secondary and tertiary amines. Tertiary amines can be used as sole curing agents but in adhesive formulations they are more normally found in blends, for example as accelerators with polyamide systems(4) and as an essential part of polysulphide systems. The cured resins tend to be less temperature and chemical resistant than the amines described above. Secondary amines react first like primary then as tertiary amines. 

Polysulphides. Liquid polysulphide rubbers have been used as hardeners for epoxy resins for many years. However, they are generally used as blends with tertiary amines and will be considered further as flexibilisers. 

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The reaction is completed after 6—8 h at 95°C volatiles, water, and some free phenol are removed by vacuum stripping up to 140—170°C. For resins requiring phenol in only trace amounts, such as epoxy hardeners, steam distillation or steam stripping may be used. Both water and free phenol affect the cure and final resin properties, which are monitored in routine quaHty control testing by gc. OxaHc acid (1—2 parts per 100 parts phenol) does not require neutralization because it decomposes to CO, CO2, and water furthermore, it produces milder reactions and low color. Sulfuric and sulfonic acids are strong catalysts and require neutralization with lime 0.1 parts of sulfuric acid per 100 parts of phenol are used. A continuous process for novolak resin production has been described (31,32). An alternative process for making novolaks without acid catalysis has also been reported (33), which uses a... 

Prices of phenolic resins vary substantially depending on the appHcation. In 1995, the price of general-purpose and semisoHds was 1.50— 1.80/kg, whereas epoxy-hardener grades can exceed 2.20/kg. Because raw materials of phenoHc resins are derived from cmde oil and natural gas, the prices of phenohc resins depend on the prices of these resources. 

Other modifications of the polyamines include limited addition of alkylene oxide to yield the corresponding hydroxyalkyl derivatives (225) and cyanoethylation of DETA or TETA, usuaHy by reaction with acrylonitrile [107-13-1/, to give derivatives providing longer pot Hfe and better wetting of glass (226). Also included are ketimines, made by the reaction of EDA with acetone for example. These derivatives can also be hydrogenated, as in the case of the equimolar adducts of DETA and methyl isobutyl ketone [108-10-1] or methyl isoamyl ketone [110-12-3] (221 or used as is to provide moisture cure performance. Mannich bases prepared from a phenol, formaldehyde and a polyamine are also used, such as the hardener prepared from cresol, DETA, and formaldehyde (228). Other modifications of polyamines for use as epoxy hardeners include reaction with aldehydes (229), epoxidized fatty nitriles (230), aromatic monoisocyanates (231), or propylene sulfide [1072-43-1] (232). 

Polyamide Resins. Another class of polyamide resins, in addition to the Hquid resins used as epoxy hardeners, are the thermoplastic type, prepared generaHy by the condensation reaction of polyamines with polybasic fatty acids. These resins find use in certain hot-melt adhesives, coatings, and inks. Diamines, typicaHy EDA (233), are the principal amine reactant however, tri- and tetramines are sometimes used at low levels to achieve specific performance. 

Epoxy hardener will strongly affect chemical resistance. 

The following coating resins were used (1) a vinyl ester (Dera-kane 470 from Dow Chemical) (2) a polyester (Atlac 382-05 AC from ICI) and (3) four epoxy resin/hardener combinations. The details of the resins and hardeners used are shown in Table I. One of the epoxy/hardener combinations was represented by materials from two sources. 

Materials Description. Three CIBA-GEIGY epoxy/hardener systems were studied Araldite 6010/906, Araldite 6010/HY 917 and Araldite 6010/972 with stoichiometries 100/80, 100/80 and 100/27, respectively. Araldite 6010 was a DGEBA epoxy resin. The hardeners 906, HY 917 and 972 were, respectively, methyl nadic anhydride (MNA), methyltetrahydro phthalic anhydride (MTPHA) and methylene dianiline (MDA). These systems were investigated previously for the matrix controlled fracture in composites (6-8). The curing cycles used can be found in (6). The ideal chemical structures of the systems are shown in Table I. Neat resins were thoroughly degassed and cast into 1.27 cm thick plates for preparation of test specimens. 

The carboxyl terminated polybutadiene (C-3000) is about equally effective to CTBN in heat distortion temperature and impact but considerably less effective in strength. From the haze data (the percent haze of ERL-4221 modified with 10 phr of CTBN and C-3000 were 17 and 85% respectively) it is quite clear that this elastomer (C-3000) is highly incompatible with the epoxy-hardener system in the cured state. A 2000 molecular weight polybutadiene elastomer, containing no carboxyl groups, was completely incompatible with the epoxy system and segregated in the cured state. 

The final sintered specimen was mounted and polished in epoxy (ME14730 epoxy resin and epoxy hardener) for electron microprobe analysis (EMPA, JEOL JXA-8600). The backscattered electron image shown in Fig. 2a confirmed a homogeneous single phase of LSFTO. Elemental compositions were determined with the probe placed at several different spots on the sample. The composition ratios were determined from the average data to be La Sr... 

Figure 8.12 TEM photographs of triblock copolymers dispersed in a DGEBA-diamine epoxy network. The triblock copolymer is polystyrene-b-polybuta-diene-b-poly(methyl methacrylate), and the epoxy hardener is (a) -methylene bis [3-chloro-2,6 diethylaniline], MCDEA, and (b) 4,4 -diamino diphenyl sulfone, DDS. In the case of the epoxy system based on MCDEA, the PMMA block is miscible up to the end of the epoxy reaction. In the case of the epoxy system based on DDS, the PMMA block phase-separates during reaction. (From LMM Library.)... 

Shieh JY, Wang CS. Synthesis of novel flame retardant epoxy hardeners and properties of cured products. Polymer 2001 42 7617-7625. 

C = condensation, OC = oxidative coupling, PF = phenol formaldehyde, NA = crosslinking not performed-modification was aimed at network formation, BD = bis-diazonium salts, AAC = aryl acid chlorides, CC = cyanuric chloride, NEH = normal epoxy hardeners, MEA = methacrylate. 

SAFETY PROFILE Most cured resins have little or no toxicity. If curing is incomplete there may be residues of highly toxic curing agents such as the organic amines m-phenylene diamine, diethylene triamine, tetraethylene pentamine, and hexamethylene tetramine, as well as phthalic anhydride and related compounds. When heated to decomposition they emit highly toxic fumes. See also various epoxy hardeners and POLYMERS, INSOLUBLE. 

The prepolynier can be reacted further with a wide variety of reagents, and its latent Functionality depends on the particular reaction. The conversion of an epoxy polymer to an interconnected network structure is formally similar to the vulcanization of rubber, but the process is termed curing in the epoxy system. When the epoxy hardener is a primary or secondary amine like m-phenylene diamine the main reaction is... 

Epotuf [Reichhold], TM for epoxy resins, epoxy hardeners, and epoxy esters used as coating vehicles. 

Symmetrical and mixed secondary alkylamines with the general formula of R-NH-R and R-NH-R, respectively are used as epoxy hardeners and plant protecting agents. Lower aliphatic secondary amines are frequently prepared by the alkylation of a primary amine or ammonia with an alcohol on a nickel or copper catalyst [1]. In this work highly selective preparation of di-n-propylamine (n-Pr2NH), di-i-butylamine (i-Bu2NH) and N-ethyl-N-n-butylamine (EtNH-nBu) is described. 

A relatively new generation of filled polyols was obtained by the reaction of an epoxy resin with an epoxy hardener in situ, in liquid polyether media. Cured epoxy resins, finely dispersed in the liquid polyether (with around 20% solid content), are obtained. 

Epoxy-terminated oxazolidone prepolymers were prepared by using a ratio of NCO epoxide of 1 2. These prepolymers could then be cured with conventional epoxy hardeners or catalysts ... 

Dodecenyl Succinic Anhydride. [Humphrey] Alkenyi succinic anhydrides intermediate for producing amide and imide rust inhibitors, sludge dispersant for lube oils and greases, industrial cleaners epoxy hardener, mercurial fungicide. 

Epotuf Hardener. [Reichhold] Poly-amine, polyamide, w anhydride epoxy hardener. 

Kemamine D Series. [Witco/Humko] Fatty acid propylene amines gasoline det ent, bactericide, eexrosion inhibits in petrol, prod. epoxy hardener. 

Kemamine T Series. [Witco/Humko] Fatty acid teit amines chemical intermediate f(x quat. ammonium derivs., acid scavenger in petrol, prods. epoxy hardener catalyst... 

Norcure. [Ril. Carlson/Nordiem Labs] Curing i ent, epoxy hardener. 

Araldite HT 907 Cyclohexane-1,2-dicarboxylic anhydride EINECS 201-604-9 Hexahydrophthalic acid anhydride Hexabydrophthalic anhydride HHPA Lekutherm Hardener H NSC 8622 NT 907. Widely used as an epoxy hardener. It may also be used in the manufacture of alkyd resins, plasticizers, and polyesters. Crystals mp = 32 bpi 8 = 145. Buffalo Color Corp. 

Research, production, and CTS worked together on the design and manufacture of a unique liquid epoxy resin and epoxy hardener. At the same time, sales, market research, and merchandising were alerted and were asked to provide information on customer attitudes, market potential, and advisable marketing procedure. When a satisfactory product was developed, our patent and legal departments were called in. 

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