Properties of vinyl-grafted h-BN/PDMS coatings and their protective effects on mortar surfaces

This study presents the development of h-BN/PDMS composite coatings through hydroxylation treatment and modification of hexagonal boron nitride (h-BN) using a vinyl silane coupling agent. The study aims to address the limitations of conventional PDMS coatings, specifically their inadequate mechanical strength and poor resistance to weathering. The innovation lies in the improved dispersion of h-BN within the PDMS matrix, which was achieved via the surface grafting of vinyl groups. This approach, combined with the intrinsic layered structure and high thermal conductivity of h-BN, led to a synergistic enhancement in the mechanical performance and protective functionality of the coating. Experimental results demonstrated that incorporating 8 % modified h-BN increased the tensile strength of the coating to 5.206 MPa, an improvement of 110.6 % over pure PDMS, and reduced erosion depth to 2.7 μm. Furthermore, the coating exhibited minimal adhesive strength loss after UV aging (from 1.085 to 1.012 MPa). Under acidic conditions (pH = 2), the composite coating reduced the mortar strength loss by 53.1 %. In seawater immersion and 25 freeze-thaw cycles, the mass loss rates of the test blocks decreased by 55.9 % and 90.4 %, respectively. In addition, the high UV reflectance (97.6 %) and oxygen barrier properties of h-BN significantly mitigated the photo-oxidative degradation of the PDMS matrix. This study proposes a theoretical foundation and process optimization strategy for designing high-performance protective coatings suitable for use on concrete and electronic components in extreme environments.