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Wollastonite Powder

Commodity: Wollastonite Powder

Size: 60mesh, 100mesh, 150mesh, 325mesh etc.

Whiteness: 70-90

Moisture: 0.2-1%

Aspect ratio: 1:10 - 1:15

Sedimentation:  40-65 (30min.)

Bulk Density: 0.38-0.45g/cc

Detailed Introduction

Wollastonite is a calcium inosilicate mineral (CaSiO3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolomite is subjected to high temperature and pressure, which sometimes occurs in the presence of silica-bearing fluids as in skarns or in contact with metamorphic rocks. It is named after the English chemist and mineralogist William Hyde Wollaston (1766–1828).

Wollastonite is a natural mineral with many unique characteristics. Through advanced processing technology, it has become one of the most widely used functional fillers on the market. Wollastonite improves the performance of many products, including plastics, paints and coatings, building materials, friction, ceramics, and metallurgical applications.

Wollastonite is an industrial mineral chemically composed of calcium, silicon and oxygen. Its molecular formula is CaSiO3, and its theoretical composition is 48.28% CaO and 51.72% SiO2. Natural wollastonite may contain trace or small amounts of various metal ions, such as aluminum, iron, magnesium, potassium, and sodium. Wollastonite itself is rare and usually contains other minerals that are removed during processing, such as calcite, garnet, and diopside. Wollastonite is a calcium metasilicate mineral, available in two powder grades of fineness. The viscosity of each paint in the paint is lower than the viscosity indicated by its oil absorption value. The low oil absorption of wollastonite allows you to reduce the cost of raw materials by replacing vehicles. The relatively high pH of wollastonite (10-11) is particularly useful in maintaining the required alkaline pH of water-based paints and preventing premature rusting of water-based paints. Wollastonite is an excellent extender pigment for powder coatings and solvent-based and water-based coatings.

The fine-grade wollastonite is dispersed to 4 Hegman at a weight of 3 pounds per gallon. This grade can provide a smooth paint film and is a universal extender. The ultra-fine grade is dispersed to 6 to 7 Hegman fineness at a pressure of 3 pounds per gallon. This grade is suitable for liquid industrial and corrosion-resistant coatings, powder coatings and semi-gloss architectural coatings. In powder coatings, this grade is ideal for smoother films and improved gloss.

Optimal performance can be achieved by correctly matching the correct coupling agent to the polymer system at the correct concentration level. In general, the benefits of surface-modified wollastonite are improved physical properties, improved processing technology, and improved resin dispersion.

Wollastonite Powder Chemical Analysis

Element% by weight

Packing: 50kg, 1000kg, 1100kg bags.

Quantity: 20-22Mt/20’GP.

Wollastonite Powder Uses

Some of the characteristics that make wollastonite so useful are its high brightness and whiteness, low moisture and oil absorption, and low volatility content. Wollastonite is mainly used in ceramics, friction products (brakes and clutches), metal manufacturing, paint fillers and plastics

Ceramics: Wollastonite can be used in a variety of ceramic applications, including ceramic glazes and porcelain, enamels, glass frits, fluxes and sanitary ware. This industrial mineral is the source of CaO in alkaline glaze formulations, which can increase the strength of the glaze. The LOI of wollastonite is also very low (<1%), and the gas generated during the firing process is the least, thus forming a smooth surface and reducing pinholes. Due to its needle-like structure, wollastonite improves green strength and reduces cracks and cracks, especially during rapid heating and cooling. Its sintering temperature is low (about 991-1196°C), which is comparable to most natural glass frits. In ceramics, wollastonite reduces shrinkage and gas escape during firing, increases green and firing strength, maintains brightness during firing, allows rapid firing, and reduces cracks, cracks and glaze defects

Plastics: Among plastics, wollastonite improves the durability of composite materials due to its needle-like or needle-like structure. It also enhances electrical insulation, increases fire resistance, and improves dimensional stability. Compared with other materials, finer particle size can improve scratch resistance and impact resistance. After surface treatment such as silane on the wollastonite substrate, the mineral has changed from a practical filler to a functional component of the polymer composite. This in turn increases the performance value that the base resin does not possess. Optimal performance can be achieved by correctly matching the correct coupling agent to the polymer system at the correct concentration level. In general, the benefits of surface-modified wollastonite are improved physical properties. In plastics, wollastonite improves tensile strength and flexural strength, reduces resin consumption, and improves thermal stability and thermal stability at high temperatures. Dimensional stability.

Construction: Wollastonite has been found to replace asbestos and is used in refractory construction products used in the construction industry. As a functional additive, wollastonite improves flexural strength and impact strength. Its low thermal conductivity and high aspect ratio structure also make wollastonite an attractive additive for applications requiring fire resistance. Wollastonite can be used for interior and exterior building panels, roof tiles, shaped insulation products, plates, panels and siding. Wollastonite can replace asbestos in floor tiles, friction products, insulation boards and panels, paints, plastics and roofing products. It has chemical resistance, inertness, stability at high temperatures, and improves flexibility and tensile strength

Paints and coatings: In coatings, fine needle-like particles can be used as a good leveling agent and settle the coating after application to form a dry film with uniform thickness, while interlocking particles can improve the toughness and durability of the coating , And has excellent color retention, frosting, and weather resistance. High brightness and whiteness reduce the pigment load, usually very low oil absorption, reduce the amount of binder required, and help reduce the cost of pigments. As mentioned earlier, wollastonite can also act as a pH buffer to improve the stability of the paint in the tank over a long period of time. The needle-like structure and alkalinity of wollastonite also make it an ideal auxiliary pigment in industrial coatings and primers to improve corrosion resistance. As an additive in paint, it can improve the durability of the paint film, and be used as a pH buffer, improve its weather resistance, reduce gloss, reduce pigment consumption, and be used as a matting agent and suspending agent.

Metallurgy: In metallurgical applications, the reasons for using wollastonite are low water solubility, low ignition loss, and high Ca-Si ratio. Wollastonite is usually added to formula powders for steel casting and welding. When the ratio of CaO/SiO2 is 1, it is easy to absorb Al2O3 which is harmful to the finished steel. Adding wollastonite to metallurgical flux can provide fusibility, good insulation properties and low viscosity. Because wollastonite is a natural low-temperature flux, it has been accepted by the flux formulation used in continuous casting of steel. When molten steel is continuously poured from a ladle or tundish, casting powder is used to maintain surface defects, prevent steel from oxidizing, lubricate the mold wall and absorb harmful inclusions. In metallurgical applications, wollastonite is used as a welding flux, a source of calcium oxide, a slag regulator, and protects the surface of molten metal during the continuous casting of steel

Friction: Wollastonite is used as a reinforcing additive in many friction applications due to its physical structure and non-hazardous properties. It is also a partial/full substitute for asbestos, ground fiber, chopped glass and synthetic materials. Its main applications are semi-metallic and non-asbestos formulations for truck blocks, drum liners, disc pads and friction paper. The benefits of using wollastonite in friction formulations include improved physical and mechanical properties, reduction or elimination of cracks, improved preform strength, improved friction stability, reduced noise, and reduced raw material and unit cost (density).

Wollastonite is used in many industries, mostly by tile factories which have incorporated it into the manufacturing of ceramic to improve many performance parameters, and this is due to its fluxing properties, freedom from volatile constituents, whiteness, and acicular particle shape.

Wollastonite is used in a cement announced in 2019 which "reduces the overall carbon footprint in precast concrete by 70%."

In metallurgical applications, wollastonite serves as a flux for welding, a source for calcium oxide, a slag conditioner, and to protect the surface of molten metal during the continuous casting of steel.

As an additive in paint, it improves the durability of the paint film, acts as a PH buffer, improves its resistance to weathering, reduces gloss, reduces pigment consumption, and acts as a flatting and suspending agent.

In plastics, wollastonite improves tensile and flexural strength, reduces resin consumption, and improves thermal and dimensional stability at elevated temperatures. Surface treatments are used to improve the adhesion between the wollastonite and the polymers to which it is added.

As a substitute for asbestos in floor tiles, friction products, insulating board and panels, paint, plastics, and roofing products, wollastonite is resistant to chemical attack, inert, stable at high temperatures, and improves flexural and tensile strength.


Wollastonite Powder advantage.

•Based on the versatility of the needle-like shape, low gloss, paint film strength and overall durability can be achieved

• Moderate oil absorption, can provide more PVC

•High dry brightness, can provide cleaner tones

•Medium hardness, can prevent scratches and scrub resistance

•Alkaline pH may become one of the most important properties of wollastonite, requiring less ammonia and improving rust and mildew resistance

Physical properties & Composition

Wollastonite occurs as bladed crystal masses, single crystals can show an acicular particle shape.

The streak of wollastonite is white, its Mohs hardness is 4.5–5 and specific gravity is 2.87–3.09. Its melting point is about 1540 ˚C.

History of Wollastonite Powder

Wollastonite is a calcium metasilicate mineral (CaSiO 3), which may contain small amounts of iron, magnesium and manganese to replace calcium. It is usually white. When impure limestone or dolomite is sometimes in metamorphic rocks, it is formed when subjected to high temperature and high pressure in the presence of silica-containing fluids. Related minerals include garnet, Vesuvite, diopside, tremolite, aconite, plagioclase feldspar, pyroxene and calcite. It is named after British chemist and mineralogist William Hyde Wollaston (1766–1828).

Wollastonite was used as a functional filler for coatings as early as the mid-1940s. In 1950, wollastonite was used as a filler in paint. The attractive properties of minerals include white color, medium hardness and high natural brightness.

In 1979, a review of wollastonite and its applicability in coating systems pointed out that this mineral has a history of 25 years as "an incremental pigment that helps resist rust, improve external durability and maintain color" Up. This article describes a study comparing wollastonite with various extenders in internal and external latex paints. The use of wollastonite in acrylic alkyd modified latex paint containing zinc oxide is also reported. Using 400 mesh wollastonite, zinc oxide can be stabilized without a large amount of dispersant. The two benefits noted are effective raw material cost management and better packaging stability.

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