Effects of surface preparation on the adhesion of UV-aged polyurethane coatings

This paper focuses on the manufacturing and quality evaluation of polyurethane coatings deposited onto composite substrates. Various methods of surface preparation and roughness development were used to enhance adhesion: degreasing with acetone, abrasive blasting with F30 alumina, abrasive blasting and degreasing with acetone, and no preparation. As well as the influence of substrate preparation on the pull-off strength of the coatings, the influence of ageing on the coating adhesion was also investigated. This research shows that the choice of preparation of the laminate substrate has a significant impact on its surface roughness, which directly affects the strength of adhesion of polyurethane coatings to the composite substrate. The most effective method of surface modification turned out to be the use of abrasive blasting for coatings applied with the traditional method (increasing the strength by 41%). Coatings subjected to the process of accelerated ageing through ultraviolet radiation are characterised by a significant reduction in the adhesion force to the composite substrate in comparison to unaged coatings. The photodestruction of UV-aged coatings was documented by the characteristics obtained during tests carried out with differential scanning calorimetry and Fourier-transform infrared spectroscopy (in the attenuated total reflectance mode). Thermal analysis (thermogravimetric analysis/dynamic thermogravimetry) also was used to study the effect of ultraviolet radiation on the coatings.