Rational design of a novel siloxane-branched waterborne polyurethane coating with waterproof and antifouling performance

Inferior water resistance remains a bottleneck in the development of the waterborne polyurethane (WPU) coatings industry . Herein, a novel strategy for the facile preparation of hydrophobic antifouling WPU coatings is presented in this work. Specifically, a series of siloxane-branched modified polyurethanes (BSi-WPU) was prepared by synergistically introducing diol-hydroxyl single-ended silicone oil (DSSiO) as the branched modified monomer and hydroxylated fluorinated siloxane (HTFSi) as the functional soft-chain segment into the WPU system via a simple polycondensation process. The effects of the introduction of DSSiO on the water resistance and mechanical properties of the BSi-WPU were investigated, and the antifouling and chemical resistance of the modified coatings were also examined. The results demonstrated that the branched DSSiO possessed excellent surface migration efficiency, which effectively improved the water repellence (contact angle up to 109.3°), waterproofness (absorption reduced to 7.5 %), and hydrolysis resistance (minimum 1.6 % loss of strength after water immersion) of the coatings. In addition, owing to thermodynamic immiscibility, the incorporation of HTFSi and appropriate DSSiO amounts enlarged the microphase separation of the polyurethane , whereby the material exhibited improved mechanical properties over ordinary polyurethanes. More importantly, based on the surface enrichment of low-surface-energy silicon and fluorine units, the coatings exhibit excellent repellency to contaminated liquids and corrosive chemical solutions. This approach provided a more applicable alternative idea to the industrial fabrication of hydrophobic and antifouling WPU coatings.