Process characteristics of kaolin
Non plasticity <1 viscosity is a characteristic of a fluid that hinders its relative flow due to internal friction. Its viscosity is used to indicate its size (the internal friction force applied to 1 units per unit area). The unit is Pa. S. Viscosity measurements are generally made using rotational viscometer to measure the rotational speed in kaolin slurries containing 70% solids. Viscosity is very important in the process of production. It is not only an important parameter of ceramic industry, but also a great influence on the paper industry. According to data, foreign kaolin as paint, coating at low speed requires viscosity of about 0.5Pa - s, high-speed coating requirements of less than 1.5Pa - S.Thixotropy refers to the characteristics of a fluid that has become gelatinous and no longer flowing. It becomes fluid after stress and gradually becomes intact after being stationary. The size is expressed by a thickening factor and measured by an outflow viscometer and a capillary viscometer.Viscosity and thixotropy are related to the mineral composition, particle size and cation type in the mud. In general, the content of montmorillonite is fine, the particles are fine, and the exchangeable cations are mainly sodium, with high viscosity and high coefficient of change. Therefore, it is often used to increase the viscosity and thixotropy of plastic clay, improve the fineness and so on, and reduce it by increasing dilution, electrolyte and water content. The drying performance of kaolin clay material in the drying process. Including drying shrinkage, drying intensity and drying sensitivity.
The brightness and whiteness similar process properties, equivalent to 4570 a; (a) white light irradiation wavelength.The color of kaolin is mainly related to its metal oxides or organic matter. Containing Fe2O3 was rose red, brown and yellow; containing Fe2+ was pale blue, pale green with pale brown; MnO2; organic matter tends to yellow, gray, green, black and other colors. The presence of these impurities, reduced the natural whiteness of kaolin, in which iron and titanium minerals will also affect the whiteness of the calcined, porcelain stains or scars appear. Kaolin formed by the combination of mud with water, under the action of external force deformation, external force is removed, the nature can still maintain this deformation is plasticity. Plasticity is the basis of the forming process of kaolin in the ceramic body, and also the main technical index. Plasticity index and plasticity index are usually used to indicate the plasticity. Plasticity index refers to the moisture content minus plastic limit water content of kaolin clay material liquid limit, expressed as a percentage of the plastic index W =100 (W -W liquid limit and plastic limit). The forming performance of the plasticity index representative of kaolin clay material, direct determination of available mud ball compression breakage when the load and deformation with plastic instrument, kg cm said, often plasticity index is high, the better the performance of its forming. The plasticity of kaolin can be divided into four grades.
Whiteness is one of the main parameters of kaolin's technological properties. Kaolin with high purity is white. Kaolin whiteness, natural whiteness, and whiteness after calcination. For ceramic raw materials, the whiteness of calcined is more important, the higher the whiteness of calcined, the better the quality. The ceramic process stipulates that the drying temperature is 105 degrees centigrade and the classification standard is the natural whiteness. The calcined 1300 DEG C is the grading standard for the whiteness of the calcined products. Whiteness can be measured by a whiteness meter. Whiteness meter is a measure of a 3800 - 7000 (i.e., 1 =0.1 nm) wavelength of light reflectivity of the device. In the whiteness meter, the reflectivity of the sample to be measured is compared with the reflectance of the standard sample (such as BaSO4, MgO, etc.), i.e., the whiteness value (such as whiteness 90, which represents 90% of the standard sample reflectivity).
