Synergistic Enhancement of Polymer–Cement Waterproof Coatings by Silane-Functionalized Cellulose Nanofibril

To enhance the mechanical properties and waterproof performance of polymer-cement (JS) waterproof coatings, cellulose nanofibrils (CNFs) were surface-modified using vinyltriethoxysilane (VTES). The modified cellulose nanofibrils (m-CNFs) were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) analysis, and energy-dispersive X-ray spectroscopy (EDS). JS waterproof coatings incorporating m-CNFs were subsequently prepared. The performance and mechanism were systematically evaluated using the tensile strength, bonding strength, water absorption, contact angle, permeability test, durability test, scanning electron microscopy, Brunauer-Emmett-Teller (BET) and atomic force microscopy (AFM). The results indicated that the coating exhibited optimal performance when 1 wt% m-CNFs were incorporated. Under this condition, the tensile strength and bonding strength increased by 33.8% and 9.8%, respectively, while the 7-day water absorption decreased by 72.9%. The contact angle reached 97.1°, and the durability of the coating was also improved. Moreover, the amphiphilic nature introduced by silane modification effectively improved the interfacial adhesion between the organic and inorganic phases within the coating. In addition, due to their water absorption capacity, m-CNFs fill the micropores of the coating during the curing process and produce an internal curing effect, thereby reducing the porosity of the material. As a result of these synergistic effects, the mechanical strength and hydrophobicity of the JS waterproof coating are significantly enhanced. This study expands the application of CNFs, a sustainable nanomaterial, in building waterproofing materials.