Modified Aliphatic Amines

Whereas most room temperature curing epoxy adhesives are cured with aliphatic amines, polyamides, or amidoamines, most elevated-temperature curing epoxy adhesives are cured with aromatic amines, modified aliphatic amines, alcoholic and phenolic hydroxyls, acid anhydrides, Lewis acids, and a host of other curatives. Latent curing agents, such as dicyan-diamide and imidazoles, are typically used in one-component epoxy adhesives systems. 

Accelerators for dicyandiamide cured epoxy adhesive formulations include tertiary amines, modified aliphatic amines, imidiazoles, and substituted ureas. All except the substituted ureas can cure epoxy resins by themselves. All these materials provide good latency and excellent adhesive applications. 

The three main types of hardeners used with the Bisphenol A resin are aliphatic amines, modified aliphatic amines, and aromatic amines. Silica is the filler most often used with epoxy mortars. This prohibits the use of epoxy mortars with hydrofluoric acid, other fluorine chemicals, and strong, hot alkalies. Carbon fillers can be substituted but with some sacrifice to the working properties. 

Aliphatic amines Modified aliphatic amines Aromatic amines Bisphenol A F ... 

Figure 19. Multifunctional nature of quinine as a catalyst. The various parts of the molecule fill the following roles (a) hydrogen bond forming ligand forming with metals (b) basic amine (c) aliphatic hydrocarbon—bulk (d) handle to modify (e,f) epimers available few conformers (g) aromatic hydrocarbon—bulk, polarizable (h) handle to modify steric and polar influence.

Table 12.9 shows a formulation for an accelerated general-purpose one-component, dicyandiamide cured epoxy adhesive compared to one with a modified aliphatic amine curing agent. Notice that the dicyandiamide cured system provides a higher glass transition tem-... 

TABLE 12.9 Formulations for a Dicyandiamide and Modified Aliphatic Amine Cured... 

Formulations for a dicyandiamide and modified aliphatic amine cured epoxy adhesive... 

All amine functional curing agents, for example, aliphatic polyamines and their derivatives, modified aliphatic amines and aromatic... 

Modified aliphatic polvamines. These are room temperature curing agents formed by reacting excess aliphatic amines with epoxy-containing materials to increase the molecular weight of the amine to reduce its vapor pressure. The performance properties of amine adduct cured systems are not significantly different from those of aliphatic polyamines. 

Primary and secondary aliphatic polyamines, their derivatives, and modified aliphatic polyamines and aromatic amines react with and cure epoxy resins as indicated earlier. The aliphatic systems usually give adequate cures at room temperature (7 days above 60 F) however, under most conditions aromatic amines are less reactive and require curing temperatures of about 300 F to give optimum cured polymer properties. 

Chem. Descrip. Modified aliphatic amine Uses Epoxy curing agent for laminates, fast-set adhesives, castings, and tooling compds. accelerator for Genamid 250,490,747 Features Offers faster cure times, lower reaction temps. exc. chem. and heat resist. 

Chem. Descrip. Modified aliphatic amine Uses Epoxy curing agent/hardener... 

Chem. Descrip. Modified aliphatic amine adduct Uses Accelerator for polyamides or the sole epoxy curing agent for low temp., chem. resist, coatings, for maintenance, marine coatings, and winter-applied coatings... 

Commercial cement modifiers used were based on a bisphenol A-type epoxy resin, diglycidyl ether of bisphenol A (DGEBA), which was mixed with three types of hardeners, modified polyamide-amine (MPAA),modified aliphatic polyamine (MAPA).and modified amine (MA) at the hardener contents recommended by the respective manufacturers. The hardener content was expressed as follows ... 

Toxicity of the polyamines can, however, be avoided by using modified aliphatic polyamines. These are obtained by the addition of polyamines to a variety of compounds such as diglycidyl ether, ethylene oxide, styrene oxide, halohydrin ethers and acrylonitrile or with polymers containing functional groups known to react with amines (other than epoxides). 

The modified procedure involves refluxing the N-substituted phthaUmide in alcohol with an equivalent quantity of hydrazine hydrate, followed by removal of the alcohol and heating the residue with hydrochloric acid on a steam bath the phthalyl hydtazide produced is filtered off, leaving the amine hydrochloride in solution. The Gabriel synthesis has been employed in the preparation of a wide variety of amino compounds, including aliphatic amines and amino acids it provides an unequivocal synthesis of a pure primary amine. 

The procedure is modified for the reaction of preformed cyanohydrins with chiral amines39. I11 a further variation, Schiff bases of aliphatic aldehydes with optically active 1-arylalkyl-amines are transformed with liquid hydrogen cyanide to the corresponding a-aminonitrilcs, which, after acid hydrolysis, give the /V-aryUilkylamino acids. Hydrogenation then yields the a-amino acids40 41. 

This combination of the modified Bratton-Marshall reaction with prechromato-graphic derivatization with N-methyl-N-(4-aminophenyl)-amine allows specific detection of isocyanates, that is especially applicable to aliphatic isocyanates. 

Inspired by the results of aromatic-ring hydroxylation from the laboratory of Karlin and co-workers, a few groups provided further examples of such reactivity, including some structurally characterized complexes of modified m-xylyl-based pyridine-donor ligands (Schiff base and non-Schiff base acyclic ligands), as well as aliphatic amine donor ligands (179) (Cu-Cu 2.990 A),169 (180) (Cu-Cu 3.015 A),170 and (181) (Cu-Cu 2.999 A).171 172 A m-xylyl-based ligand system that was used by Mukherjee and co-workers in the formation of complex (181) also resulted in the isolation of a bis(/i-hydroxo)dicopper(II) complex (182) (Cu-Cu 3.004 A).171,172 Casella and co-workers demonstrated that when their dicopper(I) complex... 

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