Preparation and performance of phosphogypsum surface hydrophobization via F-POSS coating

Gypsum is an environmentally friendly, healthy, and low-cost building material. However, its poor water resistance significantly limits its application in the construction field. In this study, octa(heptadecafluorodecyl) polyhedral oligomeric silsesquioxane (F-POSS) is synthesized as a hydrophobic agent and applied to gypsum-based flat panels via a simple brush-coating process to construct a hydrophobic coating. The microstructure, water contact angle, and abrasion resistance of the resulting hydrophobic coating on gypsum substrates are systematically characterized. The results show that, compared with the unmodified gypsum board (CA = 85.27°), the hydrophobicity of the gypsum substrate is significantly improved after surface modification, with the contact angle increasing to 135.8°. Notably, after abrasion testing, the hydrophobicity does not deteriorate but instead increases by 7.2%, reaching a contact angle of 145.67°. To further elucidate the underlying mechanism, 3D surface profilometry is employed to characterize the surface roughness and topographical complexity of the gypsum boards before and after hydrophobic modification. These results demonstrate that the prepared hydrophobic material exhibits promising application potential for enhancing the water resistance of gypsum-based materials.