Curing agents vapor pressure

Some curing agents can also be used to form adducts with epoxy resins, and these adducts, in turn, offer unique curing properties with other epoxy resins. Adducts are commonly used in adhesive formulations to reduce the vapor pressure of the system, to modify the reactivity of the system, to improve mix ratios so that they are closer to equal parts of the resin component and of the curing agent component, and to provide a certain degree of flexibility into the end product. 

Diethylenetriamine and Triethylenetetramine. Diethylenetriamine (DETA) and trieth-ylenetetramine (TETA) are very reactive, low-viscosity liquids that are widely used with DGEBA epoxy resins. The application characteristics and cured properties of adhesive formulations prepared with these two curing agents are very similar. The lower vapor pressure of TETA generally favors its use. 

Solvents and diluents are used to lower the viscosity of epoxy resins systems either to permit easy compounding with other ingredients or to aid in application of the adhesive onto a substrate. Both solvents and diluents are low-molecular-weight liquid compounds that are chemically and physically compatible with epoxy resins and their curing agents. They differ primarily by their vapor pressure. 

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. 

Most of the amines, may irritate skin, possess a noxious odor or emit corrosive fumes. Hence they are mostly sold as modified variations with reduced vapor pressures and tendency to irritate. One approach to formulate amine cross-linkers with higher equivalent weight and lower toxic hazard is to make amine-adducts by reacting standard liquid bisphenol A epoxy with excess of a multifunctional amine. A variety of amines can be used to provide adducts with a range of cure rates and pot lives. A simple epoxy-amine adduct is shown below. In two of the superprimer formulations water-borne epoxy-amine adducts are used as the curing agents [11, 62]. 

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