Anticorrosive waterborne polyurethane coatings derived from castor oil and renewable diols

Abstract

Although vegetable oil-based waterborne polyurethane (WPUs) possesses unique advantage like environmental friendliness, the shortcomings of low mechanical properties havehampered its practical implementations. In this work, sustainable diols, isosorbide (IS) and L-tyrosine derived cyclic dipeptide (L-CD), were employed into the anionic castor oil based WPU backbones via a molecular design strategy respectively (denoted as WPU-A and WPU-B). Their impact on the stability of the dispersion as well as the performance of casting films were investigated thoroughly. Result shown that the tensile strength of the films reached up to 29.56 MPa, while the toughness remained at 20.12 MJ/m−3, outperforming the state-of-art castor oil-based WPU systems. Specifically, WPU-B films exhibited superior performance than WPU-A ones possessing the similar hard segment contents, which presumably attribute to a higher density of hydrogen bonds within the network. The glass transition temperature (Tg) of WPUs were tailored in the range of 5.93 °C to 57.23 °C, and the highest value was prominent in the reported systems. Interestingly, the incorporation of sustainable diols into WPUs improved the anticorrosion performance towards 45# steel, which stemmed from the robust, hydrophobic properties of the WPU films. This study offered strategies for tailoring the physical properties of environmental benign WPUs and paved the ways towards developing high performance coatings for anticorrosion applications.