Epoxy amidoamines

Table 11.5 shows a typical formulation for an accelerated and unaccelerated epoxy-amidoamine adhesive system. The accelerated formulation provides a faster-curing adhesive, but it is not as flexible. Common fillers such as alumina, talc, and silica can be incorporated up to a level of 100 pph before any deleterious effect on properties is observed. 

As a family of curing agents for epoxy resins, the amidoamines are lower in viscosity than the polyamides. They exhibit very good adhesive properties due to their chemical structure and easy penetration. Amidoamine cured epoxy adhesives have shown very good properties on concrete and other porous substrates. They cure extremely well under humid conditions. In fact amidoamine cured epoxy formulations have been used to cure underwater in certain applications. A typical general-purpose room temperature curing epoxy-amidoamine system is described in Table 11.7. This adhesive is used as a general-purpose metal-to-metal adhesive and body solder in the automotive industry. 

Conacure AH-35 Conacure AH-66 curing agent, epoxies Amidoamine Aminoethylpiperazine ... 

Amidoamines Reduced volatility Convenient mix ratios Good toughness Poor elevated-temperature performance Some incompatibly with certain epoxy resins General-purpose adhesives Construction adhesives Concrete bonding Toweling compounds... 

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. 

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. 

The polymercaptans can also be used to accelerate the curing of epoxy resins systems blended with polyamines, amidoamines, or amines. The other curatives serve as the base to accelerate mercaptans, and the mercaptans react rapidly, generating the heat to accelerate the cure with the other hardener. 

The pot life of polyamide or amidoamine cured epoxy adhesives is generally on the order of hours at room temperature. Full cure is achieved in 5 to 7 days at room temperature, and handling strength is achieved in about 16 to 24 h. A faster cure can be achieved in 20 min to 4 h by heating to 60 to 150°C. When room temperature cures are required, an accelerator such as an amine is often added to the formulation. 

TABLE 11.5 General-Purpose Epoxy Adhesive with Amidoamine Curing Agents4... 

As with amidoamine and polyamide cured adhesives, epoxy resins cured with aliphatic amines exhibit tensile shear strength that is dependent on the type of filler and concentration. Table 11.10 shows the effect of filler loading on strength of a simple general-purpose, room temperature curing epoxy adhesive composed of liquid DGEBA epoxy mixed with 10 pph of a tertiary amine. 

DGEBA epoxy resin (e.g., Epi-Rez 510) Amidoamine (e.g., Epi-Cure 8525) Aluminum T-60 Thixotrope... 

Although most epoxy adhesives have good weather resistance, optimum properties are generally achieved when the adhesive has a combination of good water resistance and thermal shock resistance. Figure 11.6 illustrates the retention of tensile shear strength of copper and aluminum strips bonded with an amidoamine cured epoxy after 2 years of weathering in a temperate climate. 

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. 

Table 14.4 presents formulation information for bisphenol A and polyfunctional epoxy resin emulsions that are cured with an aliphatic amidoamine curing agent. Adhesive performance data are also provided for substrates common to the automotive industry. Both formulas are based on a 1 1 epoxy-amine stoichiometry and they are reduced to 45 percent nonvolatiles with water. The working life of each system is several hours at room temperature. 

General-purpose epoxy adhesive with amidoamine curing agents Effect of fillers on tensile shear strength of polyamide cured epoxy... 

Typical formulation for an epoxy adhesive cured with an amidoamine Typical epoxy adhesive cured with triethylenetetramine (TETA)... 

Cycloaliphatic, amidoamine, and aliphatic epoxy curing com pounds... 

Genamid . [Henkel] Amidoamine resin epoxy curing t ent used fex coatings, castings, potting, laminating, and adhesives. 

VeX 11-548. [Henkel] Water-reducible amidoamine resin epoxy curing agent... 

Houston, TX), EPON Resin 828 is an epoxy oligomer made from bisphenol A and epichlorohydrin, while EPIKURE 3046 curing agent is an amidoamine mixture [1],... 

L. Moshinsky, S. Kenig, H. Dodiuk-Ke-nig, A. Buchman, Epoxy Adhesives and Primers Based on Hyperbranched Poly-amidoamines . Meeting of the Adhesion Society, Williamsburg, VA, Eeb. 2000. 

Chem. Descrip. Modified cycloaliphatic amine epoxy Uses Epoxy curing agent for high solids coatings accelerator for polyamide and amidoamine curing agents Features Good chem. resist, and low temp, cure (30-35 E) exc. blush resist. 

Consider the properties of reactive surface-active (RS) substances (alkyl phenol oxyethylated ester (OP-10), dodecyl nitrile (DDN)) and of chemically indifferent smface-active substances (IS) like the ohgo-amidoamines L-18, L-19, L-20 capable of reacting with such oligomeric solvents as the ED-20 and DEG-1 epoxy resins and polyoxypropylene-triol (POPT) of molecular weight 750. These oligomers are imasso-ciated low-polarity liquids, as confirmed by the data of Table 2.1. 

Uses Antioxidant stabilizer catalyst intermediate R.T. epoxy curing agent activator for epoxy resins cured with wide variety of hardener types incl. polyamide, amidoamines, polymercaptans, and anhydrides for coatings, adhesives, castings, potting, encapsulation Manuf./Distrib. ChemService http //www.chemservice.com, Sigma Trade Name Synonyms Ancamine 1110 [Air Prods./Perf. Chems. http //WWW. airproducts. com]... 

The amine-reactive nitrile liquids are useful in formulating a modified hardener package through admixture with an amine, amidoamine or fatty poly-amide curing agent of choice (14). And novel elastomer-modified epoxy resin hardeners giving excellent reported adhesive properties have begun to appear in the marketplace (15). 

Modified polyfunctional aliphatic amines, amidoamines and fatty polyamides are covered for both CTBN/epoxy adducts or ATBN hardener systems (42,44). Examples of systems based on selected epoxy-anhydride (45), an amine-ether (46) and Lewis acid/amine complexes (47) augment this information base. Dicyandiamide (1-cyano guanidine) containing systems alone (48) and with melamine (49) and various proprietary accelerators (50-53) are shown to serve as latent, one-component film and paste adhesives with an excellent balance of adhesive properties. 

Pg. 4 - Para 2. CTBN as free dibasic acid does deteriorate all amine, amidoamine or polyamide cured epoxy adhesives if it exists as free acid. This is why the overwhelming majority of instances adducts CTBN and epoxy first. No free acid. 

Other curatives, which react through addition mechanisms are phenolic resins, particularly if the hydroxyl/epoxy reaction is catalysed using a tertiary amine (usually accomplished at elevated temperatures), thiols, polysulphides and mercaptans (can be formulated to give very rapid cures), polyetheramines (relatively slow cures, which can be accelerated with nonyl phenol), polyamides (less reactive than their amine counterparts) and amidoamines (characterized as having very long pot lives). 

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