Effect of Shellac Microcapsules Blended with Carbonyl Iron Powder and Carbon Nanotubes on the Self-Healing and Electromagnetic Wave Absorption Properties of Waterborne Coatings on Fiberboard Surface

An orthogonal experiment was conducted to prepare nine different coatings by changing four influencing factors of shellac microcapsule content, carbonyl iron powder (CIP) content, the content of carbon nanotubes (CNTs), and primer coating thickness. By testing the morphology and performance of the shellac microcapsules, CIP, CNT blended coatings (SCCBC), and using the elongation at tensile failure of the SCCBC as the orthogonal experimental analysis, it was determined that the biggest factor affecting the elongation at tensile failure of SCCBC was the shellac microcapsule content. With the aim of further optimizing the properties of the SCCBC, a single-factor experiment was performed using shellac microcapsule content as the sole variable, and it was determined that the SCCBC exhibited optimal performance when shellac microcapsule content reaches 4.2%. The optical properties of SCCBC were tested, showing that there were minor fluctuations in the glossiness and color difference of the SCCBC. The mechanical properties of SCCBC were tested. The presence of shellac microcapsules can contribute to an improvement of the SCCBC toughness, restraining the formation of microcracks, and have a certain self-healing effect. The electromagnetic wave absorption properties of the mixed powder of shellac microcapsules, CIP and CNTs were tested. The CIP and CNTs can enhance the electromagnetic wave absorption properties of the waterborne coating, but the electromagnetic wave absorption properties were weaker in low-frequency bands. The SCCBC on the surface of fiberboard not only have a self-healing effect, but also have a certain electromagnetic wave absorption function through the mixing of shellac microcapsules, CIP, and CNTs, expanding the application range of waterborne coatings for wood.