Vapor phase white carbon black (scientifically known as fumed silica) is a fine, unique amorphous powder material prepared by hydrolysis of dichlorosilane through a high-temperature hydrogen-oxygen flame. The average primary particle size is about 7-40 nm, the aggregate particle size is about 200-300 nm, the specific surface area is 50-380m2/g, the product purity is high, and the SiO2 content is not less than 99.8%. It is a multifunctional additive, widely used in the coating industry, and can play a thickening, thixotropic, extinction, Anti sinking, and other functions. Generally, there are two types of fumed silica products: hydrophilic and hydrophobic. Hydrophobic products are obtained through surface chemical treatment using hydrophilic products. Rheological aids: Rheology is an essential property of coatings, which directly affects the appearance, construction performance, storage stability, and other properties of layers. However, different coating systems have additional requirements for rheological aids. For oily systems, most rheological aids function by forming hydrogen bonds. The untreated fumed silica aggregates contain multiple hydroxyl groups, one being isolated and undisturbed free hydroxyl groups; The second is the bonded hydroxyl groups that are linked and form hydrogen bonds. Secret hydroxyl groups account for 12 to 15% of the surface groups of fumed silica, and hydrogen-bonded hydroxyl groups account for 28 to 35%. Hydrogen-bonded hydroxyl groups are elementary to form a uniform three-dimensional network structure in oily systems. This three-dimensional network structure (hydrogen bond) will be destroyed by mechanical effects (shear force), resulting in a decrease in viscosity, and the paint will restore good fluidity; When the shear force is eliminated, the three-dimensional structure (hydrogen bond) will recover, and the density will increase. In completely nonpolar liquids, the viscosity recovery time only takes a fraction of a second.
In contrast, the recovery time in polar liquids is more extended, depending on the concentration and dispersion of fumed silica. This characteristic endows oil-based coatings with excellent storage and construction performance, especially for thick paste coatings (such as marine paints), which ensures good layer fluidity under a specific construction shear force and the primary construction thickness of the coating film. If you are looking for high quality, high purity and cost-effective fumed silica, or if you require the latest price of fumed silica, please feel free to email contact mis-asia.
