What are the performance characteristics of kaolin

The common main use of kaolin is inseparable from its high-quality physical and chemical properties. High quality kaolin has high fineness, soft texture, easy dispersion and floatation in water, excellent plasticity and high adhesion, high-quality insulation performance, excellent acid suppression and solubility, low positive ion exchange capacity, high fire resistance, and other physical and chemical properties.

1) The color tone is milky white or tends to be milky white, with a maximum fineness exceeding 95%.

2) The strength of soft plastic kaolin is generally 1-2, while the strength of hard kaolin can sometimes reach 3-4.

3) Particle size distribution and particle shape The Particle size analysis of kaolin is generally 0.2-5 μ m. The particle size distribution has influence on its plasticity, slurry viscosity, ion-exchange capacity, formability, dryness, sintering and other properties. Generally, the denser the particle size distribution of kaolin is, the better its plasticity is, and the higher its dry compressive strength is, which is convenient for sintering. The porosity after sintering is low and its impact toughness is high. Many fields and industries have unique regulations on the particle size distribution of kaolin. For example, the particle size distribution of kaolin used as printing paper sizing, high gloss paint, printing ink, industrial ceramics and vulcanized rubber is less than 2 μ A portion of m cannot be less than 80%. The shape of kaolin particles is also crucial for their practical value, such as the size grade kaolin required for the production of copper sheet paper, which must be in block form.

4) Plasticity is the fundamental process for forming kaolin in porcelain bodies and a key industrial production performance indicator. Kaolin has excellent forming, drying, and sintering properties. The key factors endangering the plasticity of kaolin are: particle size distribution: the denser the particle size distribution of kaolin, the larger the particle size distribution, and the larger the specific surface, the better the plasticity. Positive ion exchange ability: The larger the positive ion exchange capacity of kaolin, the better its plasticity. Particle shape: If the shape of kaolin particles is flaky, it is easy to fuse and slide relative, and has higher plasticity than other types of particles such as plates and columns. Residue content: If there are mineral residues such as quartz and marble in kaolin, it will reduce plasticity; The plasticity will be improved when Diosmectite, diaspore or organic compounds are contained. Generally, kaolin has medium and low plasticity, which is lower than montmorillonite powder. When kaolin is heated to 400-700 ℃, its plasticity will dissipate.

5) The sintering property of sintered kaolin is one of the key processing characteristics that must be possessed in the production and manufacturing of ceramic products. Simply put, sintering refers to the efficient liquid phase caused by fusible substances filling the gaps between unmelted particles when the object is heated to a certain temperature. By relying on its interfacial tension, the porosity is reduced, the relative density is increased, and the volume is closed, resulting in increasingly high-density and hard performance. When the porosity decreases to the lowest limit and the relative density reaches the highest value, it is called the sintering condition. At this time, the matching temperature is called the sintering temperature. There are many factors endangering the sintering of kaolin, and the key is related to the whole process of ceramic manufacturing and the content of other minerals in the mud body: from the mineral composition, Illite and Diosmectite are easier to sinter than kaolin; In terms of composition, mud compacts with more Basic oxide and less dispersed SiO2 are easy to sinter; From the perspective of ceramic production, it is expected that the sintering temperature will be low and the sintering range will be wide. This will not only be environmentally friendly and energy-saving, but also conducive to real-time control. The sintering temperature range for kaolin is generally between 1000 and 1500 ℃. In the processing process, the sintering temperature and sintering range can be controlled by mixing auxiliary solutions or selecting kaolin of white clay type according to the proportion.

6) Dispersed kaolin is prone to dispersion and floatation in water, and can produce a highly reliable mixture. 7) Electrical insulation performance Kaolin has high-quality insulation performance, with a resistance exceeding 1010 Ω· cm at 200 ℃, and can be used as a filler for cable.

8) Organic chemical reliability is one of the key performance indicators of mineral raw materials as fillers. Kaolin has extremely strong organic chemical reliability and a certain degree of corrosion resistance.

9) The positive ion exchange capacity of kaolin is generally 0.03-0.05mmol/g. 10) The composition of refractory kaolin is Al2O3 and SiO2, therefore it has high-quality fire resistance performance, with a fire resistance of 1770-1790 ℃. When kaolin contains minerals such as water Biotite and marble, its fire resistance will be reduced. Generally, with the increase of Al2O3 content, the fire resistance increases; With the increase of Basic oxide and compound content, the refractoriness decreases.

11) Interaction with Soil organic matter Kaolin can interact with many optically active organic molecules, such as formamide, acetamide, urea solution, and so on to form a kaolin optically active organic molecule chimeric molecular chaperone. Organic molecules can enter the interlayer domain and are connected with the two surfaces of the solid layer by Covalent bond. The first result is to expand the thickness of the crystal lattice layer of kaolin; The second is to modify the surface properties of kaolin, such as water absorption.