Aliphatic curing agents

Designed for epoxy resin systems, Anquamine 401 and Ancamide 2424 (by Air Products) are a modified aliphatic curing agent at 70% solids in water for waterborne two-component epoxy coatings and a modified polyamide curing agent for liquid epoxy resins in two-component structural adhesives. 

Frontal polymerization works with a wide variety of systems and has been demonstrated with neat liquid monomers such as methacrylic acid, (d, 8-10) n-butyl acrylate (10), styrene, methyl methacrylate, and triethylene glycol dimethacrylate (77). Fronts can also be performed with solid monomers such as acrylamide (with initiator) (72) or transition metal nitrate acrylamide complexes (without initiator) (75). Pojman et al. demonstrated frontal polymerization of acrylamide, methacrylic acid and acrylic acid, each in dimethyl sulfoxide or dimethyl formamide (14). Frontal curing of epoxy resins has been demonstrated with aliphatic curing agents (75). 

Aliphatic and cycloaliphatic amine curing agents irritants, sensitizers, corrosive, absorbed through skin, respiratory irritants high toxicity... 

Aliphatic polyamines, amine adducts and polyamides react with epoxide resins at normal temperatures to give complexes with outstanding chemical resistance. Paints based on this type of reaction must be supplied in two separate containers, one containing the epoxide resin and the other the curing agent , the two being mixed in prescribed proportions immediately before use. 

Aliphatic aldehydes, 13 571 physical properties of, 2 60t syntheses of, 12 187 Aliphatic a-hydroxy acids, 14 130 Aliphatic amine/polysulfide co-curing agent systems, 10 410... 

Curing agents account for much of the potential hazard associated with use of epoxy resins. There are several major types of curing agents aliphatic amines, aromatic amines, cycloaliphatic amines, acid anhydrides, polyamides, and catalytic curing agents. The latter two types are true catalysts, in that they do not participate in the curing process. 

The spectra of the cured epoxies were compared. It was found that the aliphatic region of the three spectra were distinctly different. The differences were associated with the rigidity of the polymer and the differences in the chemistry of the curing agents. Anisotropy in the aromatic region broadened in the order piperidine > HHPA... 

A tertiary amino group formed in curing with aliphatic amines can sometimes catalyze the epoxy group polymerization. When aromatic amines are used as curing agents, such reactions do not take place at all. 

A great variety of aromatic diamines and aliphatic di- and poly-amines are used as epoxy resin curing agents, and tert-amines can act as catalysts for anionic epoxide homopolymerisation. 

Aliphatic or aromatic peroxide curing agents can also be used, by reactions with vinyl side chains or even saturated alkyl groups. Specihc peroxides are chosen on the basis of their decomposition temperatures, and the reaction products they leave behind after the curing process is complete. Some peroxides used are Mv(2,4-dichloroben-zoybperoxide, benzoyl peroxide, dicumyl peroxide, and di-t-butyl peroxide.83-86... 

The two homologous aliphatic diamines are commonly used as bifunctional monomers for polycondensation reactions. Hexamethylenediamine or 1,6-diaminohexane, Cf,H16N2 (CAS No. 124-09-4, PM Ref.No. 1840), which is most well-known as a polyamide (Nylon 66) monomer, is also copolymerized with sebacic acid to form Nylon 6/ 10, or with isophthalic acid. Besides that, it is applied as a curing agent for expoxy... 

The mechanisms of radiation damage and effects of hardeners were studied recently by pulse radiolysis [89], The epoxy resins require a relatively large amount of curing agents (hardeners), most of them are aromatic and aliphatic amines such as diamino diphenyl methane or triethylene tetramine. On the basis of the emission spectra and kinetic behavior of excited states observed, the radiation resistance of aromatic and aliphatic amine curing epoxy resin was explained by internal radiation protection effects due to energy transfer. 

In adhesive formulations, aliphatic amines are most commonly used to cure the DGEBA type of epoxy resin. Aliphatic amines are not widely used with the non-glycidyl ether resins, since the amine-epoxy reaction is slow at low temperatures. The reaction usually requires heat and accelerators for an acceptable rate of cure. Aliphatic amines are primarily used with lower-viscosity DGEBA resins because of the difficulty in mixing such low-viscosity curing agents with the more viscous epoxy resins. 

There are several reasons why unmodified aliphatic amines, such as those described above, are less widely used than other curing agents in epoxy adhesive systems. These include... 

Two curing agents that have found their way into many epoxy adhesive formulations are the polyamides and amidoamines. These are commonly used in the hardware store variety two-part epoxy resins that cure at room temperature. Both are reaction products of aliphatic amines, such as diethylenetriamine, and should be included under the subclassification of modified amines. However, these products have such widespread and popular use, they are addressed here as a separate classification. 

Polyamide curing agents are the reaction products of dimerized fatty acids and aliphatic amines such as diethylenetriamine. This introduces a bulky, oil-compatible, C36 carbon group between the amine sites. Similar to the diglycidyl ether adducts of aliphatic amine, they are manufactured by adding the fatty acid to an excess of amine. They are available in a range of viscosities that can be achieved by varying the amine/acid molar ratio in the reaction. 

Amidoamine or polyamidoamine curing agents have reactivity with DGEBA epoxy resins that is similar to the polyamides. However, they are lower-viscosity products and are also lower in color. Amidoamines are derivatives of monobasic fatty carboxylic acids and aliphatic polyamines. Since the amidoamines have only one amide group per molecule, they are lower in molecular weight, viscosity, and amine functionality than the polyamides. 

Table 11.8 presents a typical triethylenetetramine cured epoxy adhesive formulated with selected fillers. In this formulation the use of aluminum powder and alumina increases substantially the resistance of the adhesive to boiling water.7 This is also true when DETA is used as the curing agent.8 A typical room temperature cured aliphatic amine cured epoxy adhesive for general-purpose use is shown in Table 11.9. This shows the difference that is achieved in shear strength by curing at elevated temperatures versus room temperature.

Table 11.12 shows two rapid-setting, room temperature cure epoxy adhesives based on epoxy acrylate resins with aliphatic amine curing agents. These adhesives have gel times of less than 5 min for a 100-g mass. The bond strength development is rapid with handling strength occurring in about 1 h at room temperature. 

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