Polyurea spray elastomers offer a unique combination of properties such as rapid cure speed - even at freezing temperatures, the ability to spray high build films in a single coat, zero VOC and low temperature flexibility. The majority of polyurea systems in use today are aromatic and based on diphenylmethane diisocyanate (MDI) prepolymers, polyoxypropylene amines, and aromatic amines. These aromatic systems have poor gloss and color retention which has limited their use in exterior topcoats where long-term aesthetics are important.1 Polyurethane topcoats are commonly recommended to protect these systems in maintenance applications. Also, adhesion problems reported with early polyurea coatings have been overcome by a variety of measures such as application of a primer coat, inclusion of adhesion promoters, and mechanical preparation of the substrates.2 Another limitation is that the chemical resistance for this technology, especially to solvents and strong acids, can be poor, so immersion service is not recommended.
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