What Does Amine Cured Epoxy Coating Mean?
An amine cured epoxy coating is an epoxy coating where an anime-based hardener was used in the curation process. In the most general sense, these epoxy coatings are described on the molecular level as having anime and alcohol functional groups formed during the curing. Four classes of amine hardeners are available:
- Aliphatic amines
- Polyamides and amidoamines
- Cycloaliphatic amines
- Aromatic amines
Typically, the reason an amine cured epoxy coating is used in a particular industrial application has to do with the ability for amine hardeners to react at ambient temperatures. These epoxy solutions are often chosen for any application that is sensitive to high temperatures.
Corrosionpedia Explains Amine Cured Epoxy Coating
Amine cured epoxy coatings are prepared by combining an epoxy resin with an appropriate amine hardener. Primary (R-NH2) or secondary (R-NH-R’) amine groups attack a carbon atom of the three membered epoxide ring, leading to an opened ring with an amine group and hydroxyl group. Primary amines form secondary amines, which can react again to form tertiary amines, although at slower rates. The hardener unit may have two or more anime functional groups, enabling the hardener to cross-link across multiple epoxy resin molecules, increasing crosslink density and various resistivities of the resultant epoxy. Aliphatic amines react more readily than cycloaliphatic amines and much more so than aromatic amines, but the latter, less reactive amines tend to form epoxies of much higher temperature resistivity. Aromatic amines are no longer often used due to negative health effects of handling those corresponding compounds.
Each class of amine hardeners has its own advantages and disadvantages in terms of curing speed, chemical resistance, solvent resistance, temperature compatibility, flexibility, viscosity, mechanical strength, cross-link density, color and toxicity. In addition, each class contains a whole family of various hardeners that further vary these properties.
When choosing the right amine hardener for an epoxy in an industrial application, additional considerations should be made. Although generally a 1:1 (stoichiometric) ratio of epoxide groups in the resin and amine hydrogens in the hardener are used, in some cases an off-stoichiometric ratio yields better properties for a particular application. Increasing the temperature of the curing process increases the reaction rate and speeds up the ability to apply the epoxy coating. Finally, when considering the costs of the hardener, one must consider both the cost by weight and the amine hydrogen equivalent weight. A hardener that costs more by weight may be cheaper overall compared to another hardener in cases where its amine hydrogen equivalent has a high value.