Fluorine-free dual crosslinked polyurethane coating with self-cleaning properties for fat oil and grease deposition control in the sewer system

Sewer concrete pipelines are continuously exposed to aqueous environments enriched with organic and inorganic contaminants as well as diverse microbial communities, which collectively contribute to surface deterioration and fat, oil, and grease (FOG) accumulation, leading to sewer blockages. To address this challenge, we introduce a dual-crosslinking strategy that combines a renewable bio-based polyol (sorbitan monooleate) with 2,4,6-tris[bis(methoxymethyl)amino]-1,3,5-triazine (TBMMAT) to engineer a low-energy, hydrophobic surface within polyurethane networks. This approach simultaneously increases crosslink density and suppresses polar functionalities, resulting in coatings with high water repellency and exceptional self-cleaning properties. Upon crosslinking with TBMMAT, the polyurethane coating exhibited a substantial reduction in surface energy, from 30.69 mN m -1 to 16.27 mN m -1 , while maintaining an adhesive strength of 3.4 ± 0.4 MPa, resulting in a pronounced improvement in hydrophobicity, as evidenced by a water contact angle of 104°. Under simulated sewer conditions, the engineered polyurethane reduced FOG deposition by 64.8%, demonstrating its potential to significantly mitigate urban wastewater blockages. This scalable, environmentally benign process provides a pathway to next-generation protective coatings for infrastructure applications, combining durability, fouling resistance, and sustainable materials design. • Surface-engineered polyurethane coating with self-cleaning properties is developed. • The coating shows self-cleaning properties for water-based contaminants. • Bio-based sorbitan monooleate enhances coating crosslink density and reduces polarity. • Surface energy reduced by 46%, enhancing self-cleaning and anti-fouling properties. • Achieved 64.8% less FOG deposition, ideal for wastewater infrastructure protection.