Silica prepared by gas phase method usually has high specific surface area and active surface, which makes its surface modification one of the important means to improve material performance and application diversity. Through surface modification, the properties of silica such as hydrophilicity, dispersibility, reinforcement effect and compatibility with matrix materials can be adjusted. Several common surface modification methods and their effects on material properties are described below.

Modification with silane coupling agent: introduce an appropriate amount of silane coupling agent into the surface of fumed silica, and achieve modification through chemical bonding. This modification method can increase the compatibility between silica and organic matrix materials, improve the dispersion and reinforcement effect, and at the same time improve the anti-sedimentation and anti-oxidation properties of silica.

Surface coating modification: surface modification is achieved by forming a covering layer on the surface of silica, such as polymer, silicone oil or silicon dioxide. This coating layer can increase the compatibility between silica and matrix materials, improve the dispersion and reinforcement effect of fillers, reduce viscosity and improve fluidity.

Surface functional modification: introduce different functional groups on the surface of silica, such as amino, hydroxyl, carbonyl, etc., and improve the material properties through the interaction between the surface functional groups and the matrix material. For example, the introduction of hydroxyl functional groups can improve the compatibility and reinforcement effect of silica and rubber matrix.