Anticorrosive waterborne polyurethane coating with Gemini surfactant-assisted exfoliation of hexagonal boron nitride nanosheets

The uniform dispersion of hexagonal boron nitride (h-BN) in a waterborne polymer matrix remains a challenge in preparing waterborne uniform h-BN/polymer composite coating. Here, cationic Gemini surfactant (GS-16) is used as a surfactant and intercalator to exfoliate and functionalize bulk h-BN for preparing GS-16-functionalized h-BN nanosheets (G-BNNS). For comparison, the conventional hexadecyl trimethyl ammonium bromide (CTAB) surfactant with the same structural unit was utilized to prepare CTAB-functionalized BNNS (C-BNNS). Compared with C-BNNS, G-BNNS exhibits larger lateral size, lower thickness, and larger specific surface area. G-BNNS and C-BNNS are subsequently blended with waterborne polyurethane (WPU) to prepare composite coatings. Their morphologies, surface roughness, water resistance, mechanical properties and anticorrosive performance of composite coatings are comparatively studied. The water resistance, mechanical, and thermal stability of G-BNNS/WPU-0.3 wt% composite films are higher than that of C-BNNS/WPU-0.3 wt% and WPU films. The impedance modulus of G-BNNS/WPU-0.3 wt% is four orders of magnitude higher than that of pristine WPU and at least one order of magnitude higher than C-BNNS/WPU-0.3 wt%. GS-16 is demonstrated to be an effective surfactant and intercalator to exfoliate and functionalize h-BN. The as-prepared G-BNNS is also certified to be a high-performance anticorrosive filler for waterborne polymer-based coatings.