Effect of resins on the salt spray resistance and wet adhesion of two component waterborne polyurethane coating

Abstract

Effects of the type, chemical structure and NCO/OH of resins on wet adhesion and salt spray resistance of two component waterborne polyurethane coating were studied in this paper. The content of functional groups in resins and films were analysed by areas of their FT-IR absorption peak to study the relationship with anticorrosive performance of coatings. Coatings based on resins with more-OH tend to have stronger wet adhesion and salt spray resistance because resins with more-OH have more possibilities to react with-NCO to form a compact film with a higher crosslinking degree. The wet adhesion of coatings after 8 h of immersion deteriorated from level 1 to level 5 with the increase of NCO/OH due to the decrease of-OH in coatings to link with substrates. And excess-NCO tend to react with H2O to generate CO2 to form cracked physical bubbles, which would weaken the wet adhesion.