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【Huayuan wollastonite】Do you know all these ten uses of w
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  • 发布时间:2020-03-27 11:32
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Do you know all these ten uses of wollastonite?
 
Wollastonite products can be divided into high aspect ratio wollastonite and ground wollastonite. The former mainly uses its needle like physical and mechanical properties and is widely used in plastics, rubber, Asbestos Substitutes, paint coatings and other fields. It can increase the hardness, bending strength and impact resistance of products, improve the electrical properties of materials, and improve the thermal stability and dimensional stability. It is a promising application field of * * *. The latter is mainly used in ceramic and metallurgical industries. The SiO2 and Cao components in wollastonite provide low expansion rate and good thermal shock resistance.
 
Brief introduction of various applications of wollastonite:
 
1. For rubber
 
In different products, the specific wollastonite powder is used to replace lithopone, part of titanium dioxide, silica, light calcium, clay, etc., and the performance indexes of products are mostly improved. The application results show that wollastonite can improve the covering ability of white colorant and play a certain role in whitening; when used in light colored rubber, it can replace titanium dioxide, clay and lithopone in a large amount and play a certain role in reinforcing and reducing the product cost. The combination of wollastonite and coupling agent can improve the properties of the compound and expand its application.
 
Various rubber products
 
2. For ceramic raw materials
 
Wollastonite can be used to prepare various kinds of electromagnetic ceramics, building ceramics and household ceramics. The quality requirements of wollastonite are sio238% ~ 58%, cao36% ~ 55%, CO2 ≤ 6%, Fe2O3 ≤ 1.7%. Ceramic raw materials account for 40% - 45% of the total consumption of wollastonite in the world. Wollastonite can compact the ceramic structure, improve the mechanical strength, reduce the wet expansion coefficient, improve the strength of the green body and the quality of pressing, reduce the firing temperature, shorten the firing cycle, and achieve the purpose of energy saving and efficiency increasing.
 
Using wollastonite as raw material of building ceramics can reduce the temperature of plain firing by 200 ℃ (from 1280 ℃ to 1080 ℃), and shorten the period of plain firing from 58h to 24h. In the glaze industry, using wollastonite as raw material in glaze brick can realize fast firing at low temperature and save 30% oil in plain firing; moreover, it can improve the whiteness of glaze, improve the flow performance and reduce the prick point of products. Wollastonite can improve the thermal shock resistance of the green body and generate calcium feldspar (melting point 1550 ℃) by solid-state reaction, which can realize rapid sintering at low temperature. The micro wollastonite chain enhances the connection between the glass phase particles, so that the products can withstand the special machining such as sawing and drilling, and it also provides a low loss insulating crystal phase, which can be used as electrical ceramics and electronic ceramics.
 
3. Substitute glass fiber as reinforcing filler of plastics
 
Wollastonite for packing is an application field with high potential, added value and rapid growth rate. At present, this field accounts for about 25% of the world's total consumption of wollastonite. Wollastonite can replace or partially replace glass fiber as reinforcement of polymer composites, improve material properties, reduce costs, and play a dual role of increment and reinforcement. At present, the application research of wollastonite is focused on the application of wollastonite filled composite materials in the fields of electronic components, packaging materials, high-performance rubber and plastic products, automobile shell, mold and optical disc materials. ***The filling amount of wollastonite reinforced nylon modified by coupling agent is up to 50%, the impact strength is increased by more than 20 times, and the moisture absorption rate is very low; the ultra-fine modified high long warp ratio wollastonite and carbon fiber filled polytetracycline resin can be made into durable and non leaking automatic sealing ring body, which can be used in pressure reducing valve, butterfly valve and compressor repeated shaft.
 
4. As asbestos substitute
 
Wollastonite is an ideal substitute for short fiber asbestos because of its needle like properties, low thermal expansion and excellent thermal shock resistance. Wollastonite as a substitute for asbestos accounts for 20% - 25% of the total consumption of wollastonite in the world. The friction materials made of wollastonite with high friction coefficient instead of asbestos are mainly used in brake pads, valve plugs, automobile clutches and other fields. Some studies have shown that the brake patch with wollastonite needle powder partially replacing asbestos has good comprehensive performance, its friction coefficient is relatively stable below 300 ℃, the heat recession is not obvious, the recovery is good, the friction loss rate is small, the impact strength of the product is reduced but higher than the national standard.
 
Acicular wollastonite powder
 
5. As filler of paint and coating
 
Wollastonite has bright color and high reflectivity. It is suitable for producing high quality white paint and clear and transparent colored paint. The quality requirements of paint coating for wollastonite are as follows: SiO2 ≥ 49%, Cao ≥ 45%, Fe2O3 ≤ 0.2%, oil absorption of 325 mesh ore powder is 20-25g / 100g, water soluble matter ≤ 0.5%, and water extraction pH value is 7-9325 mesh ore powder whiteness ≥ 90%. Acicular wollastonite is a good flatting agent with high color coverage and uniform distribution. It has the characteristics of UV resistance, and is widely used in interior wall coating, exterior wall coating, special coating (especially fire retardant coating) and emulsion paint. Using wollastonite powder instead of titanium dioxide to produce paint coating can not only improve the color of products, improve the smoothness of paint, enhance the tensile strength of paint, reduce cracks, but also reduce the oil absorption and enhance the anti-corrosion ability. The finer the particle size, the higher the whiteness and pH value, the better the paint color and coating performance, and the alkaline paint can be used as anti-corrosion coating for metal equipment such as steel parts. Wollastonite can also be used as the filler of paint, which can improve the physical and chemical properties, durability and weather resistance of the product, and reduce the fracture and aging of the paint.
6. For metallurgical casting materials
 
The basic requirements of mold casting for mold flux are low density, low melting point, the ratio of CaO / SiO2 less than 1, proper melting speed and better spreading property. Wollastonite has the characteristics of low-temperature melting aid, stable chemical composition, high purity and neutral alkalinity (CaO / SiO2). This excellent property provides an ideal raw material for the protective casting material of metallurgical steelmaking, especially the tiny Al2O3 in wollastonite, so the metallurgical protective slag has a strong ability to absorb the harmful Al2O3 in steel water, so it is widely used in metallurgical industry. It is required that wollastonite ≥ 50%, calcite ≤ 50%, quartz ≤ 5%, s ≤ 0.01%, P ≤ 0.01% in raw materials of metallurgical auxiliaries. In the world, 12% - 15% wollastonite is consumed in this field every year.
 
At present, from ordinary carbon steel, manganese steel to stainless steel continuous casting, slag type from small square billet, bloom, large plate billet to furnace refining, etc., are widely used with wollastonite as the base material of the protective slag, which quickly replaced the expensive imported protective slag, promoting the development of the metallurgical steel industry.
 
7. For the preparation of bioactive materials
 
Artificial bone is usually made by coating a layer of bioactive ceramic material on the surface of titanium alloy. This kind of artificial bone has the advantages of high strength and good toughness, but its composition is quite different from that of human bone tissue, so it is difficult to achieve true healing and easy to be corroded. Many scholars' researches show that the bioceramics prepared with wollastonite as the main raw material have high biological activity, high strength, good stability and good compatibility with human bone tissue, which are expected to be applied in the field of artificial bone. Three kinds of inorganic fillers, apatite wollastonite (AW), apatite (HA) and β - tricalcium phosphate (β - TCP), were selected respectively to compare the histocompatibility and binding state between the cement powder and the real bone. The results showed that two weeks after AWC transplantation, the uncured bis GMA based resin surface layer was filled with newly formed bone like tissue, and aw glass ceramic particles were surrounded by bone tissue and tightly bound with bone tissue through apatite, without intermediate soft tissue; the other two kinds of cement powder had good biocompatibility, but it took a long time.
 
Artificial spine image
 
8. As the raw material of white carbon black
 
Silica is a synthetic amorphous silica ultrafine particle (particle ≤ 0.3 μ m), which has the properties of acid resistance, alkali resistance, high temperature resistance and good electrical insulation and dispersion. It is widely used as the thickener and anti sink agent of rubber, sealant, paper, plastic, cable, filler, cover agent and paint ink. SiO2 with high specific surface area has honeycomb porous structure, which can be used as a new catalyst carrier, selective adsorbent and thermal insulation material for aviation in high-tech field. The purity of calcium in wollastonite is over 94%, and the impurities are less. It can be dissolved in wollastonite. It is an ideal raw material for the preparation of silica
 
9. Other uses
 
Wollastonite with a small amount of wollastonite can be made into the indispensable silicon fertilizer in the growth and development of rice. The coating of wollastonite electrode can effectively restrain the discharge during welding, improve the melt fluidity, make the weld neat and beautiful, and enhance the mechanical strength. In addition, wollastonite has prospects for development in composite materials, FRP, asbestos products, biogas digesters, foam sponge, white cement, paper making and so on.
 
Wollastonite is one of the few special-shaped minerals with many excellent properties, which can adapt to a variety of industrial applications and will be more widely used in the future industry. The industry should continuously improve its physical and chemical properties, such as emphasizing the deep processing of wollastonite, especially the development of modified wollastonite products with high aspect ratio; expanding the application of wollastonite in plastics, high-quality paint coatings, friction and bioactive materials; attaching importance to the development of equipment and process suitable for the production of Wollastonite with high aspect ratio; The synergistic effect of wollastonite with mica, kaolin, quartz, talc and other hybrid particles in polymer composites was studied to improve the comprehensive properties of the materials. To broaden its application field and increase its market capacity are the key points of future work.