Research on the aging mechanism of polyurea-based coatings due to effects of UV radiation exposure

Accelerated aging of polyurea coatings by UV radiation under laboratory conditions is tested. The results of coating color and gloss measurements indicate that the gloss and color of the polyurea coating are significantly changed. The coating gloss is decreased sharply from 72.12 GU to 1.93 (decreased by 97.3%) GU after 1000 hours of aging under UV radiation. The total color difference ΔE*ab is increased up to 13.67 after 1000 hours of testing, and the color of the coating tends to change to yellow. Based on the SEM imaging method, it shows that the microscopic surface of the coating is cracked. Such cracks increase in terms of quantities, numbers, and width with deeper propagation into the coating when increasing the aging time by UV radiation. Through the IR spectrum analysis method, it also demonstrates that the bonds of functional groups characterized by polyurea are also destroyed. The polyurea chain destruction is increased with the increase of UV aging time, some bonds of the N-H group, and the C=O group in polyurea are completely destroyed when increasing the aging time to 1000 hours.