The term ‘polyurea’ has been wrongly used in the past. The urethane coatings chemistry can be divided into three sub segments:
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 spray coatings technology is one of the new developments of the last 20 years. This technology combines fast curing, even at very low temperatures, and water insensitivity with exceptional mechanical properties, chemical resistance and durability. The development of new raw materials and improved spray equipment has made it possible to overcome the initial problems of this technology such as substrate wetting, intercoat adhesion and surface finish quality.
The latest development programs are focussing on the extension of the application fields through the introduction of MDI-prepolymers combining low viscosity with low NCOcontent, resulting in slower reactivity and/or higher flexibility. Alternatively, prepolymers with higher NCO-content produce coatings with superior hardness. This paper details the technology, eradicates the misconceptions and provides an update on the latest developments in the field of raw materials, formulation and application performance for polyurea spray.