Observation of the Effect of Aging on the Structural Changes of Polyurethane/Polyurea Coatings

Abstract

In this study, polyurethane/polyurea coatings were exposed to four different types of aging: aging in the natural environment (NC), accelerated ultraviolet aging (UV), aging in a sodium chloride solution (NaCl), and thermal aging (TC). To monitor the changes that occurred during these processes, the thickness was measured and microscopic and macroscopic observations were conducted continuously. The samples aged under various conditions were then subjected to spectroscopic (FTIR) and thermal (TGA) analysis to determine the possible structural changes in the coatings. The dependence of aging conditions on the physicochemical properties of the tested coating surfaces was thoroughly investigated and characterized by the water contact angle and surface free energy. Adhesion tests were performed after the established aging period. The results show that different aging conditions have a tremendous effect on the appearance and pull-off strength. The coatings that age in a NaCl solution are more affected in terms of their adhesion.

Keywords

• aging
• adhesion
• pull-off test
• atmospheric aging
• polyurea/polyurethane coatings
• surface wettability