Aging behavior of the three-proof polyurethane coating under UV radiation

The influence of UV radiation on the gloss, structure (SEM, FTIR), thermal (TGA, DTG) and mechanical properties of polyurethane resins and the three-layer protective coating made of them was investigated. The gloss of the resins was greater than that of the protective coating. UV radiation has been proven to reduce gloss (at 1,200 hours irradiation, 81.3 degrees to 8.9 degrees for resins, and 61.1 degrees to 2.8 degrees for coat-ing).The tensile strength of the resins decreased during aging, and the relative elongation at break after reaching the minimum was increased (at the irradiation time of 100 h). In the case of coating, both the tensile strength and elongation decreased during aging and, after reaching the minimum they in-creased (at the irradiation time of 800 h), reaching the maximum (at the irradiation time of 1000 h), and then decreased.