Wollastonite is widely used in ceramics, plastics and asbestos substitutes, metallurgy and coating for its low water absorption, thermal stability, conductivity and chemical inertness. So far, around 600,000t wollastonite is consumed every year in the world, about 40%~50% in ceramics, 20%~25% in plastics, 20%~25% in asbestos substitute, 10% in metallurgy and 5% in pigments and other industries. High slenderness ratio wollastonite (15:1~20:1) is used in coatings, plastics and rubbers as reinforcing material to increase the stiffness, flexural stability and impact resistance as well as improve the electrical property of plastics, increase its thermal stability, corrosion and wear resistance. It can also be used to produce friction materials, insulation materials and flame retardants. Milled wollastonite (3:1~5.1for low slenderness ratio wollastonite) is used as raw material for CaO and SiO2 in producing ceramics and glass, and as low-temperature flux metallurgy. The world consumption structure of wollastonite is presented in Table 1.
Table 1 World consumption structure of wollastonite products in recent years
Table 1 indicates that wollastonite is mainly used in the world as functional fillings for ceramics, plastics, rubbers and paintings/coatings. Ceramics, as the largest user of wollastonite, consumes nearly half of the world’s wollastonite output every year. As a ceramic raw material, wollastonite also adds to the strength of ceramic products, reduces its cracks and glazing spots, increases the surface gloss of the glazing material and cuts down on the fuel consumption (by 60%). In this respect, wollastonite is an energy-efficient ceramic raw material with high development potential. Some experts predict the demand for wollastonite of ceramic purposes will increase at 5% every year.
Acicular wollastonite powder is a nontoxic harmless acicular structure that is used as a partial substitute for asbestos, glass fiber and paper pulp of a lower price. As extended exposure of asbestos to the air causes environmental pollution, the use of asbestos is restricted or prohibited in many countries in the world. It is therefore quite natural that wollastonite, with its thermal stability, reinforcing properties and toxic and harm-free nature, has become the best substitute for asbestos. Over the past years, more and more wollastonite is being used as a substitute for short fiber asbestos and 35,000~40,000t high slenderness ratio wollastonite is consumed in building materials and insulators every year. It is mainly used in refractory wall boards, cement materials and friction materials. Other applications include interior wall boards, roof tiles, high-temperature insulation bricks and boards. Friction materials originally containing asbestos are now made of high friction level acicular wollastonite. These mainly include brake pads, valve plugs and car clutches. This market is in steady increase in many parts of the world.
Wollastonite growth areas of consumption is the fastest in the plastics industry. Adding wollastonite powder in plastic, plastic products can improve the tensile strength and flexural strength, reduce the amount of resin, can improve the plastic thermal stability at high temperatures and shape stability, needle-like wollastonite powder with surface treatment can improve the adsorption of wollastonite and organic polymer strength, improving the forming properties of products, widely used in automotive plastics, PP, PV, PVC and other plastic products, at present, plastic car market has become the fastest growing areas of consumption of wollastonite.
High purity silica powder, as a white inorganic pigment, is widely used in paint, can replace titanium dioxide expensive; in light-colored rubber products also can replace a part of anatase titanium dioxide, titanium dioxide, the price is only 1/10.
The wollastonite main consumption countries and regions: Europe, America, Japan have, India, Mexico, China. Wollastonite North America's main consumption in ceramic industry, but the per capita consumption of ceramic tile are lower than in Asia and europe. Europe wollastonite consumption is mainly used for ceramic industry and metallurgy industry, India wollastonite consumption mainly used for ceramics and coatings industry. China's main consumer in wollastonite glazed tiles and ceramic blank, accounting for more than 50% of the total consumption of wollastonite; other consumer areas of plastics, rubber, paint, metallurgy, architecture and asbestos substitute. At present Chinese wollastonite annual consumption of about 100000 t. The main areas of consumption is about 55%; ceramics, metallurgy, accounted for about 30%; other (plastic, rubber, paper, paint, electric welding rod) accounted for 15%.
The United States is an important wollastonite consumer in the world. In 2002, nearly the same volume of wollastonite was sold inside China as in 2001, with an increase in the plastics consumption and roughly the same or marginal reduction in other consumptions. From the product category, the economic slowdown and price competition from other countries resulted in a reduction in the sales volume of low-value wollastonite products in the United States. While the sales volume of high-value wollastonite products had a slight increase, the total volume was still limited. Thus little impact was caused to the total wollastonite sales volume inside China. In the United States, wollastonite is typically consumed by ceramics, metallurgical, coating and plastics industries. Its recent consumption structure of wollastonite is approximately 37% in plastics, 28% in ceramics, 10% in metallurgy, 10% in coatings, 9% in friction products and 6% for other applications.