Preparation and Properties of High-Performance Polyurea Powder Coatings via Electrostatic Spraying

Although spray polyureas are the most widely applied and commercialized choice, too short operable time and too high requirement on specialized equipment limit the expanding of applications. Powder coating technology is therefore chosen in this study for polyureas with high toughness and high melting temperature. A series of biobased polyurea coatings derived from 1,6-diaminohexane, 1,10-diaminodecane, and urea were first prepared by a four-step approach from melting polycondensation, wet-method pulverization, electrostatic spraying, and then to infrared baking. The structure of the polyureas has been verified via NMR and FTIR spectra, and the GPC results further confirmed that the polyureas possess high molecular weight. The particle size of the polyurea powder is approximately 20 μm. The obtained coatings have high gloss (90–110 GU), transparency, and smoothness, as well as excellent flexibility (1 mm rod) and impact resistance (100 kg cm). The results in neutral salt spray tests show that all polyurea coatings except PUr-10 exhibit excellent corrosion resistance, with all corrosion widths much less than 3 mm, and no significant change is observed on undamaged coatings after the tests. The coatings also possess outstanding UV aging, acid, and alkali resistance. Such polyurea powder coatings developed in this study have extremely high application value in fields of explosion-proof and chemical engineering equipment.