Preparation and performance study of carbodiimide-modified polyurethane-acrylic resin composite coatings with high transparency, strong adhesion, and excellent weathering performance

Abstract

Aiming at the problem of insufficient weathering resistance of traditional fluorine-free transparent back sheet coatings, this study innovatively grafted carbodiimide onto polyurethane-acrylic resins through carbon‑nitrogen double bonding and carboxyl acylation reaction to develop a new type of transparent protective coatings, which possesses excellent thermal stability, strong adhesion, and resistance to humidity and heat. Meanwhile, to solve the problems of poor stability of UV absorbers and shielding agents affecting transparency, 3-Glycidyloxypropyltrimethoxysilane was coated onto the surface of cerium oxide nanoparticles using in situ modification technology, resulting in a new anti-UV agent with balanced transmittance and UV-resistant performance. The experimental results show that the initial bond strength of the coating reaches 13.15 N/cm, and it still exceeds 12 N/cm after 168 h of humid-heat aging, the yellowing index is less than 3 and the light transmittance is more than 90 % under the UV irradiation of 60 kWh-m⁻², which confirms its long-term stability in the harsh environment.