Hardeners for epoxy

Table 26.3 Typical amine hardeners for epoxy resins...

Rigid polyurethane foams were prepared at room temperature using eommercial polyols and polymerie 4,4 -diphenyl methane diisoeyanate, and used to study their reeyeling by aminolysis. The reaction products obtained by treatment with diethylene triamine at 180 C were evaluated as hardeners for epoxy resins. The exothermie heats of euring were determined over the temperature range 60-80 C by differential scanning calorimetry. A reaction order of 2.2-2.4 was obtained. 8 refs. 

Diels-Alder reactions provide one of the few general methods of forming two carbon-carbon bonds simultaneously. The main features of these reactions are described in Box 1.3. The reaction finds widespread industrial use for example hardeners for epoxy resins are made by reaction of maleic anhydride with dienes such as 2-methyl-1,4-butadiene. 

Amine hardeners -for epoxy resins [EPOXY RESINS] (Vol 9)... 

Organic phosphorus compounds are also produced in the interaction of wliite phosphorus with an epoxide or an episulfide and an alcohol or mercaptane in the presence of alkaline catalysts at 25 °C to 200 °C In order to remove P-H bonds the reaction mixture is treated witli formaldehyde and oxidized. The products are said to be useful as hardeners for epoxy resins or as antistatic agents and fire retardants. 

These resins (Resole or Novolac) are used as curing agents or hardeners for epoxy molding compounds for electronics applications such as computer components. 0-cresol-formaldehyde resins have heen also used to modify phenol-formaldehyde resins, and in laminates. 

Amines Chemical compounds with nitrogen as central atom, inter alia applied as hardener for epoxy resin adhesives. 

Tertiary butylamine is used to make accelerators and hardeners for epoxy resins [103] and Celiprolol [104], a chemical used in the treatment of hypertension and anginal pectoris. Tertiary butylamine also is used to make products of isobutylene by way of Friedel-Crafts reaction [105]. 

E. Takahashi, et al., Novel IV-methylhenzothiazolium salts as hardeners for epoxy and acrylate monomers. J. Polym. Sci. A Polym. Chem. 2003, 41(23), 3828-3837. 

Direct polycondensation of sebacic acid and adipic acid at a high temperature under vacuum resulted in low molecular weight oligomers. These oligomers were used as hardeners for epoxy resins [34] ... 

Tetrabromophthalic anhydride. Flame retardant in production of unsaturated polyester resins and rigid PU polyols co-hardener for epoxy resins cost efficient additive for latex emulsions derivatives used as flame retardants in diverse applications (wire coating, and wool, etc.). Crystals mp = 279-281 insoluble in H2O. Ethyl Corp. Great Lakes Firm Chem. 

Compositions valuable as hardeners for epoxy resins by cross-linking have been derived by the reaction of dipropylene tiiamine with aqueous formaldehyde at 60 C acompanied by water removal, addition of a phenol such as nonylphenol and further reaction at the same temperature (ref. 51). 

More elaborate examples of bisanhydrides include (251 R = CPh2) which, when polymerized with aryldiamines, gave polyether-polyimides useful for the manufacture of heat and moisture resistant optical disks <90JAP(K)0251527>. Another series (X = spirocyclohexyl orp-C(Me)2PhC(Me)2) were used to prepare heat-resistant polyether-polyimides that are useful for electronic parts <89JAP(K)01230637). Bisanhydride (252), prepared from styrene and maleic anhydride, is useful as a hardener for epoxy resins, and as a polyester and polyimide monomer <91JAP(K)03264574>. 

Examples of the resin components of expoxies are listed in Table 1. Several chemical substances can be used as hardeners for epoxies [5,6], The two main groups of cross-linking agents used in industry are two or more functionalized amines and anhydrides of carboxylic acids. Cross-linking with amines is possible at room temperature as well as at elevated temperatures, depending on the chemical structure of the amines (Table 2). Anhydrides of carboxylic acids react at elevated temperatures only. 

The most widely used epoxy resins are reaction products of either bisphenol A or a novolac phenolic resin with epichlorhydrin. When used to manufacture corrosion-resistant structures for use in the chemical process industry, epoxy resins are generally hardened with either aromatic or cycloaliphatic amines. The hardeners for epoxy resins are, with few exceptions, added at levels varying from 20phr (parts per hundred resin) to lOOphr. This means that the hardener is actually quite a high proportion of the matrix resin and has quite a profound effect on the mechanical and corrosion properties of the cured resin. Thus the selection of the most suitable hardener is critical to the eventual success of the application. Epoxy resins have viscosities of several thousand mPas at room temperature, which makes it much more difficult to wet out glass fibre efficiently with them than with polyesters. Wet-out therefore involves heating the resin formulation to between 40°C and 60°C to reduce the viscosity to less than 1000 mPas. 

Uses Hardener for epoxy resins in solv.-based paints (industrial and anticorrosion paints), solv.-free coatings, floor coatings, highly filled mortars for building trade, GRP, and encapsulating compds. for electronic components... 

Chem. Descrip. Isophorone diamine CAS 2855-13-2 EINECS/ELINCS 220-666-8 Uses Curing agent, hardener for epoxies in coatings, adhesives, castings and composites... 

Uses Chain extender for PU hardener for epoxy resins Manuf./Distrib. Lonza Ltd... 

Anhydride Hardeners for Epoxy Resins, Publieation 762-5M, Allied Chemical Co., (1962)... 

Why is vegetable oil-modified poly(amido amine) widely used as a hardener for epoxy resins ... 

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. 

Trimellitic anhydride is used as a raw material for plasticizers, as a component in polyesterimides and as a hardener for epoxy resins. High-temperature resistant and high-strength polyimides are produced by the reaction of trimellitic acid chloride with an aromatic diamine, such as 4,4 -diaminodiphenylmethane (e.g. Torlan, Amoco),... 

Hexamethylenetetramine (Hexamine) - te-tr9- inen [ISV hexa- + methylene + tetra-+ amine] (1888) (HMT, methenamine, and urotropine) n. (CH2)6-N4. A bicyclic compound, the reaction product of ammonia and formaldehyde. It is used as a basic catalyst and accelerator for phenolic and urea resins, and a solid, catalytic-type curing agent (hardener) for epoxies See image). 

Black rubber can sensitize hydraulic engineers. Assembly workers build the frame and both rivet and seal. Set-up men, riveters, retouching specialists, and engine fitter-mechanics may come into contact with sealants that may contain phenol-formaldehyde resin (Beck 1989), epoxy base (Handley and Burrows 1994), hexavalent chromate in hardeners for epoxy-based sealants (Handley and Burrows 1994) and polysulfides in two-part sealant bases (Wilkinson and Beck 1993 Bruze et al. 1996). Thiocol, a synthetic rubber based on polysulfide polymers, is used by aircraft fitters to dip screws and rivets into before use, and a fingertip dermatitis localized to the thumb and first two fingers of the dominant hand was seen in five of six fitters with positive patch-test reactions to the polysulfide-polymer-containing system (Wilkinson and Beck 1993). 

Uses solvent for sulfur, acidic gas, resin and dye intermediates for organic synthesis saponification agent for acidic materials fuel component hardener for epoxy resins Cross ethylenediamine dihydrochloride A... 

The largest use of novolak resins in coatings is as a hardener for epoxy resins. The epoxy is frequently based on bisphenol A or epoxidized novolaks. Basic catalysts such as benzyldimethylamine are required for moderate baking conditions, such as 2 h at 180°C. The phenolic/epoxy ratio is adjusted to be stoichiometri-cally equivalent in order to give a highly cross-linked coating that has moderate... 

Shieh Jeng-Yueh, and Wang Chun-Shan. Synthesis and properties of novel phosphorus-containing hardener for epoxy resins. J. Appl. Polym. Sci. 78 no. 9 (2000) 1636-1644. 

The moulding compounds used for encapsulation are a mix of a resin (either epoxy or silicone), a hardener (for epoxies either a novolac or an anhydride), an inorganic filler (such as silica or alumina) together with a mould-release agent, a flame retardant and proprietary ingredients used to optimise some characteristics of the moulding compound. 

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