Synergistic effects of perfluoropolyether alcohol modification on the hydrophobicity and flexibility of waterborne...

Waterborne nano-polyurea coatings have attracted increasing attention as eco-friendly anti-corrosion materials, but their practical application is limited by insufficient hydrophobicity and flexibility. To overcome these limitations, a fluorinated grafted MDI, synthesized using 4,4'-methylenediphenyl diisocyanate (MDI) and monohydroxyl-terminated perfluoropolyether (PFPE-OH), was introduced into a waterborne nano-polyurea system. The modified coating was comprehensively evaluated through structural characterization, analysis of physical properties, and application performance testing. The effects of PFPE-OH content on the structure and performance of the coatings were systematically investigated. The FT-IR and ¹H NMR results demonstrated successful incorporation of PFPE-OH into the polyurea network through the formation of urethane linkages, while ¹⁹F NMR confirmed the introduction of PFPE side chains. The fluorinated groups were uniformly dispersed in the modified coatings as revealed by SEM-EDS, and XPS results verified their enrichment at the coating surface, with the F atomic percentage reaching 38.92 at% for the modified sample (JM-4). With increasing PFPE-OH content, the water contact angle increased from 63.3° to 108.4°, the elongation at break first increased from 2.40% to 3.98% and then decreased to 0.69% at excessive PFPE-OH loadings, and the Shore hardness decreased from 61 to 42, indicating significant improvements in both hydrophobicity and flexibility. An appropriate PFPE-OH content also contributed to enhanced thermal stability, abrasion resistance, neutral salt spray resistance, and adhesion performance. In particular, when the MDI/PFPE-OH feed ratio was 1 : 0.08, the coating exhibited an adhesion strength of 5.33 MPa and superior overall performance. These findings demonstrate that PFPE-OH modification is an effective strategy for achieving simultaneous enhancement of hydrophobicity and flexibility in waterborne nano-polyurea coatings.