Application and consumption of Wollastonite

Wollastonite is widely used in ceramics, plastics, asbestos substitutes, metallurgy, coatings and other departments because of its low water absorption, thermal stability and conductivity, and chemical inertia. At present, the annual consumption of wollastonite in the world is about 600,000 tons, ceramics account for 40% -50%, plastics 20%-25%, asbestos substitutes 20% -25%, metallurgy 10%, pigments and others 5%. Wollastonite with high aspect ratio (15:1-20:1) is mainly used as a functional filler in coatings, plastics and rubber to improve hardness, bending strength and impact resistance, and at the same time, it can also improve the electrical properties of plastics, thermal stability, corrosion resistance and wear resistance. It can also replace asbestos in manufacturing friction materials, insulating materials and flame retardants. Grinding grade wollastonite (wollastonite with low aspect ratio of 3:1-5:1) is mainly used as raw materials of CaO and SiO2 in ceramic and glass manufacturing process and as low temperature flux in metallurgical industry. The consumption structure of wollastonite in the world is shown in Table 1. 　

Table 1 consumption structure of wollastonite products in the world in recent years

As can be seen from the above table, wollastonite is mainly used as a functional filler in ceramic industry, plastic rubber paints and coatings, etc. As the largest consumption field of wollastonite, ceramics consume nearly half of the world's output in this field every year. Wollastonite as ceramic raw material can increase the strength of ceramic green body and ceramic products, reduce ceramic fragmentation and glaze spots, increase glaze surface luster, and reduce fuel consumption (which can save 60% of fuel). Therefore, wollastonite is a promising energy-saving ceramic raw material. Some experts predict that the demand for wollastonite used in ceramic industry will increase by about 5% year by year. Acicular wollastonite powder is used in special ceramics.

Acicular wollastonite powder has an acicular structure and is non-toxic and harmless. It can partially replace asbestos, glass fiber, paper pulp and so on, and the price is relatively cheap. Because long-term exposure of asbestos to the air will pollute the environment, many countries in the world have formulated laws and regulations to restrict or prohibit the use of asbestos. Wollastonite is naturally the best substitute for asbestos because of its thermal stability, various reinforcing properties and innocuity. In recent years, the amount of wollastonite as a substitute for short fiber asbestos has increased rapidly, with 35,000 ~ 40,000 t of wollastonite with high aspect ratio being consumed in building materials, insulators and other industries every year. It is mainly used in fireproof wallboard, cement material and friction material. Other applications include indoor wallboard, roofing tiles, high-temperature insulating bricks and slabs. The original friction material of asbestos was replaced by acicular wollastonite with high friction level, mainly including brake pads, valve plugs and automobile clutches. At present, this market is growing steadily in many parts of the world.

The fastest growing consumption area of wollastonite is the plastic industry. Adding wollastonite powder into plastics can improve the tensile strength and flexural strength of plastic products, reduce the amount of resin, and improve the thermal stability and shape stability of plastics at high temperature. Needle-shaped wollastonite powder can improve the adsorption strength of wollastonite and organic polymers and improve the properties of molded products by surface treatment, which is widely used in automotive plastics, PP, PV, PVC and other plastic products. At present, the automotive plastic market has become the fastest-growing consumption field of wollastonite.

High-purity wollastonite powder, as an inorganic white pigment, is widely used in coatings and can replace expensive titanium dioxide. It can also replace a part of anatase titanium dioxide in light rubber products, and the price is only one tenth of that of titanium dioxide.

The world's main wollastonite consuming countries and regions are: Europe, the United States, Japan, India, Mexico, China and so on. Wollastonite in North America is mainly consumed in the ceramic industry, but the per capita consumption of ceramic tiles is lower than that in Asia and Europe. Wollastonite consumption in Europe is mainly used in ceramics and metallurgy industry, while wollastonite consumption in India is mainly used in ceramics and coatings industry. Wollastonite in China is mainly consumed in glazed tiles and ceramic blanks, accounting for more than 50% of the total consumption of wollastonite; Other consumption areas include plastics, rubber, coatings, metallurgy, construction and asbestos substitutes. At present, the annual consumption of wollastonite in China is about 100,000 t. The main consumption field is ceramics, accounting for about 55%; Metallurgical, accounting for about 30%; Others (plastics, rubber, paper, coatings, welding electrodes, etc.) account for about 15%. 　

The United States is an important consumer of wollastonite in the world, and the domestic sales volume of wollastonite in 2002 was basically the same as that in 2001. The sales volume in the field of plastic consumption has increased, while the sales volume in other consumption fields has basically remained unchanged or declined slightly. In terms of product types, the sales volume of low-value wollastonite products in the United States declined in 2002 due to the slowdown of American economic growth and the competition of foreign wollastonite prices. Although the sales volume of high-value wollastonite products increased, the total volume was very small, which had little impact on the total domestic sales volume of wollastonite. The wollastonite consumption areas in the United States are mainly industrial sectors such as ceramics, metallurgy, coatings and plastics. The main consumption structure of wollastonite in recent years is as follows: plastic 37%, ceramics 28%, metallurgy 10%, coating 10%, friction products 9% and others 6%.