Physical modification of nano silica
Nano silica has many advantages, such as small particle size, large specific surface area, good biocompatibility, surface interface effect, small size effect and quantum size effect.
However, there are a lot of active hydroxyl groups on the surface of nano-SiO2, which makes it easy to form agglomerate or secondary aggregation, which is not conducive to its dispersion in the material, and then affects the structure and performance of the material. Therefore, it is necessary to modify the surface of nano silica to ensure its stable storage and improve its dispersion in polymer matrix.
There are many methods to modify the surface of nano silica, mainly including physical modification and chemical modification.
Physical modification of nano silica
The physical modification of Nano-SiO2 is mainly to attract the modifier to the surface of Nano-SiO2 through adsorption, coating and other physical functions, change its surface properties, so as to reduce agglomeration and increase the dispersion stability.
The physical modifiers of nano silica mainly include surfactants, metal oxides and polymers.
The surface modification of Nano-SiO2 by physical method can prepare various materials with coating structure, which can meet different application needs. However, due to the simple adsorption or coating of nano-SiO2 particles by van der Waals and electrostatic force, the interaction between organic phase and inorganic phase is weak. When the system environment such as temperature, pH value, pressure and other conditions change, obvious phase separation may occur.