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The primary particles and aggregates of a fumed silica

The primary particles and aggregates of a fumed silica agglomerate form larger assemblies whose size is generally in inverse proportion to the primary particle size or proportion to the specific surface area. The agglomerate size also increases with the extent to which the fumed silica is compacted. The binding forces holding these agglomerates together are relatively weak. Nevertheless, a certain shearing energy is required when these agglomerates are incorporated into and broken down in a liquid system for homogeneous distribution of the primary particles and aggregates or particles with a low degree of aggregation. Depending on the particular field of application, dispersing is carried out using a very wide variety of mixing devices, with determining factors for the selection being not only the viscosity and polarity of the system but also the agglomerate strength and the desired homogeneity. With simple agitator mechanisms, such as paddle stirrers, it is usually impossible to satisfy the direct incorporation of small amounts of silicas, especially not when the systems in question are of low viscosity. However, paint and varnish makers, and those who carry out the processing, are interested in obtaining the performance-optimum distribution of the silicas, which are used predominantly as thickeners and thixotropic agents, using very simple devices with a very low energy input and in a very short time. In the case of paddle-stirrer dispersing, the coarse silica agglomerates are not sufficiently comminuted and hence can make only a small contribution to raising viscosities and thixotropy. The data relate to a UP resin (unsaturated polyester resin) as the dispersion medium. 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.

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