Construction of eco-friendly multifunctional cashew nut shell oil-based waterborne polyurethane network with UV resistance, corrosion resistance, mechanical strength, and transparency

Vegetable oil-based waterborne polyurethane possesses numerous advantages, including its sustainability, environmental friendliness, and economic benefits. Nevertheless, its application is constrained by inferior mechanical properties and a low glass transition temperature. Hereon, the renewable polyols of sorbitan monooleate/cytidine were incorporated into the anionic cashew nut shell oil-based WPU network through molecular structure design. Series of CNSL-based WPU with outstanding UV resistance, mechanical properties, corrosion resistance, and transparency were successfully synthesized. The effects of Ce/SP content on the performance of CNSL-based WPU dispersions and films were investigated. The results demonstrated a remarkable enhancement in the properties of the modified WPU films. Specifically, the tensile strength and T_g were increased from 9.7 MPa to 23.9 MPa and 1.1 °C to 45.8 °C, respectively, while maintaining a toughness of 26 MJ/m⁻³, which attained or even surpassed the current vegetable oil-based WPU systems. It was confirmed excellent UV resistance within the UVB and UVC spectrums. Furthermore, with the increase in Ce/SP content, the water contact angle of films increased slightly, enhancing its water resistance. The IE of WPU-Ce and WPU-SP films reached 97.93 % and 98.42 % respectively, indicating outstanding corrosion resistance. This work presented novel strategies for the advancement of high-performance bio-based WPU, which held promising potential in diverse areas including coatings, corrosion protection, inks, and wearable applications.