Flaking and degradation of polyurethane coatings after 2 years of outdoor exposure in Lhasa

• Published in: Chinese science bulletin 2010-03, Vol.55 (7), p.650-655
• Main Authors: Liu, FuChun, Hao, YongSheng, Wang, ZhenYu, Shi, HongWei, Han, EnHou, Ke, Wei
• Format: Article
• Language: English
• Subjects: Chemistry/Food Science; Earth Sciences; Engineering; Humanities and Social Sciences; Life Sciences; multidisciplinary; Physics; Science; Science (multidisciplinary); XPS分析; X射线光电子能谱; 扫描电子显微镜; 聚氨酯涂料
• ISSN: 1001-6538; 1861-9541
• DOI: 10.1007/s11434-009-0269-1

The exposure of a high gloss polyurethane aircraft topcoat system with polyurethane intermediate coating and epoxy primer to strong ultraviolet radiation in Lhasa, Tibet was studied by using scanning electron microscopy （SEM）, atomic force microscopy （AFM）, attenuated total reflectance Fourier-transform infrared （ATR-FTIR）, and X-ray photoelectron spectroscopy （XPS）. Micro-flakes were found to form on the topcoat surface after exposure and the size and quantity of the flakes increased with the in- crease of the exposure time. The magnitude of micro-bulges and the topcoat roughness increased after a long exposure to sunlight. Flakes and micro-bulges resulted in the loss of the topcoat gloss. ATR-FTIR and XPS analysis indicated that chain scissions of the polyurea C=O group and the polyurethane C--O--C and CO--NH groups occurred, and the degradation products of NH and carbonyl groups formed due to the exposure. The breaking of the chemical structure of the polyurethane resulted in a decrease in its elasticity and in the adhesion of the flakes to its surface.