Mechanical and electronic property improvement of the carbon fiber/silicone composite coatings by controlling the fiber diameter and surface modification

The low-temperature‑carbonized carbon fiber (CF) with different diameters modified with silane coupling agent was prepared as the fillers and added into silicone resin (SR) composite coatings, in order to investigate the effects of the diameter and modification of fibers on the mechanical and electronic properties of the CF/SR composite coatings. The results of surface microscopy and structural analysis showed that more coupling agents were coated on the surface of thick fibers (TCFs) with a larger diameter, which provided more chemical bonds and mechanical meshing than fine fibers (FCFs) with a smaller diameter. The mechanical test and electrical test illustrated that the decrease in the diameter of fibers cannot only increase the mechanical properties of the composite coatings but also enhanced the surface resistivity with fewer amounts of fibers, which reduced the cost of the application. In particular, the surface resistivity of 2wt%TCF/SR was 11.60 MΩ/square, which was 455.02 % higher than that of 2wt%FCF/SR (2.09 MΩ/square). In addition, the silane coupling agent treatment also increased the mechanical properties and the surface resistivity of the composite coating. The surface resistivity of 2wt.%FCF-A/SR was 24.94 MΩ/square, while that of 2wt.%TCF-A/SR was 60.42 MΩ/square. Meanwhile, reducing the fiber diameter and the silane coupling agent treatment could increase the dielectric constant and dielectric loss of the coating, while could also meet the requirements in the wave transmission performance during the application of coatings. This paper illustrates that reasonable control of diameter and modification is required to improve the comprehensive performance of silicone composite coatings. It guides the application in the electrical magnetic interference field as well as the improved functionality of the composites.