Definition and chemistry
The urethane coatings chemistry can be divided into three subsegments: Each segment deals with systems which can be aromatic, aliphatic, or a blend of both aromatic and aliphatic. Pigments, fillers, solvents and/or additives can be introduced to all of them.
- Polyurethane coatings
A purely polyurethane coating is the result of a reaction between an isocyanate component and a resin blend made with only hydroxyl-containing resins.
The final coating film will contain no intentional urea groups. A polyurethane system will most probably contain one or more catalysts.
- Polyurea coatings
A polyurea coating is the result of a one-step reaction between an isocyanate component and a resin blend component. The isocyanate can be monomer based, a prepolymer, a polymer or a blend.
For the prepolymer, amine- and/or hydroxyl-terminated resins can be used. On the other hand, the resin blend sho uld only contain amine-terminated resins and/or chain extenders and not any hydroxyl reactive polymer component.
- Hybrid polyurethane/polyurea coatings
A polyurethane/polyurea hybrid coating has a composition which is a combination of the above-mentioned two coating systems.
The isocyanate component can be the same as for the “pure” polyurea systems. The resin blend is a blend of amine-terminated and hydroxyl-terminated polymer resins and/or chain extenders.
The resin blend may also contain additives, or non-primary components. To bring the reactivity of the hydroxyl-containing resins to the same level of reactivity as the amine-terminated resins, the addition of one or more catalysts is necessary.
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