How does silica play an anti sinking action?What is its network structure?
By dispersing or dispersing in the paint, a network like structure is formed to achieve the purpose of erosion prevention, or adsorption on the surface of pigments and fillers, bridging between pigments, and controlling the flocculation of pigments and preventing them from sinking
Hydrogen bonding to form a contact structure. The deformation of fumed silica is an ideal anti settling agent, to prevent paint paint system of precipitation is very effective. Especially for the paste system, adding proper amount of paste stability will be greatly improved, but also can reduce the amount of wetting and dispersing agent, in order to improve the applicability of the paste and to reduce the influence of paste coating system of precipitation. The precipitation of fumed silica on coating deposited very favorable, especially some pigments such as metal powders and flakes, are easy to precipitate and not fully suspended, the use of gas phase two silicon oxide can ensure the dispersed precipitation. In nonpolar liquids, such as hydrocarbons, halogenated hydrocarbon solvent free hydrogen bonding ability, only a fraction of a second viscosity recovery time; in a polar liquid, such as having hydrogen bonding tendency of amines, carboxylic acids, alcohols, aldehydes, two alcohols. The recovery time, for several months, it depends on the concentration of fumed silica and the degree of dispersion. The gas phase silica dispersed after adding to the finished paint, in order to improve its dispersion quality, usually adopts high speed dispersion machine or three roller machine, if not fully dispersed, paint particles, impact has gloss. Many reports of fumed silica as anti settling agent is added to the copper acrylic resin conductive paint, the experiment proves that the fumed silica can make the thermoplastic acrylic resin has thixotropy, to prevent the settlement of the filler, but excessive amount of paint, gel state, conductive coating is reduced.
Fumed silica is four to silicon chloride hydrolysis in an oxyhydrogen flame. It is small in size, large surface area, with silanol groups on the surface. These interactions with adjacent silanol radical gas phase silica particles and the formation of hydrogen bonds, as shown in figure.
