Wollastonite
Wollastonite (CaSiO3) is a white, triclinic inosilicate mineral renowned for its diverse industrial applications. Formed through metamorphism, it features a chain silicate structure, with SiO4 tetrahedra forming linked chains connected by calcium ions. Insoluble in water, wollastonite exhibits stability in various chemical environments and dissolves in hydrochloric acid with carbon dioxide liberation. Mined and processed to specific particle sizes, wollastonite serves industries such as composites, construction, plastics, paints, coatings, agriculture, ceramics and foundry. Its role as a reinforcing filler, flame retardant, soil conditioner for enhancing soil fertility and flux in casting systems, underscores its significance in industrial applications .
Applications of Wollastonite:
Composites and Fibre Reinforced Plastics:
Wollastonite is non-toxic, highly chemical resistant, inert, stable at high temperatures and improves flexural and tensile strength thanks to its morphology and its interaction within the matrix. It has high abrasion and friction resistance.
Ceramics:
The inherent linear thermal expansion properties of wollastonite play a crucial role in ceramic products by minimizing product deflection, preventing micro-cracks, breakage, and glaze defects in porcelain. This, in turn, significantly elevates the yield of the final products. Notably, wollastonite products lack alkali metals, contributing to excellent electrical insulation properties, heightened impact strength, and shape stability. These distinctive characteristics render wollastonite particularly valuable in precision ceramics and the power ceramics industries.
The use of Wollastonite ceramic wall and floor tiles, can result in a significant decrease in firing temperature and a shorter firing duration for the product. This facilitates a low-temperature, rapid, one-time firing process, leading to substantial energy savings.
Paper Making:
Wollastonite mineral fiber filler, utilised in papermaking, represents an innovative category of raw material. It offers a viable alternative to traditional papermaking sources such as wood pulp, straw pulp, and waste paper pulp, particularly in the production of packaging paper. This mineral fiber filler plays a crucial role in enhancing various physical attributes of the final paper, including strength, whiteness, opacity, stiffness, and flatness.
Remarkably, the retention rate of wollastonite mineral fiber in the paper reaches up to 80%, ensuring not only satisfactory fluidity and dispersion properties that meet the requirements of the papermaking process but also significantly boosting material utilisation. This dual effect translates to a reduction in production costs for paper products and a decrease in emissions.
Friction Materials and Abrasives:
Utilising Wollastonite in friction materials and abrasives, enhances their stability, reduces cracking, significantly boosts the resistance to friction and heat, and enhances the overall physical and mechanical properties of the final products. It has the potential to substitute or partially replace other fibre-based raw materials in friction materials, leading to a reduction in production costs and an increase in the value of the resulting products. In the manufacturing of bonded abrasives and grinding wheels, it notably improves melting speed and high-temperature shock resistance. It finds application in diverse products like brake pads, linings, clutches, valve plugs, pulleys, and more.
Construction Industry:
Wollastonite finds extensive use in the construction sector, particularly in the production of high-performance concrete. Its incorporation enhances the strength, durability, and fire resistance of concrete structures. It can increase the compressive and flexural strength and the shrinkage resistance of the concrete while decreasing the capilar pores making it a more dense and robust material. It can be used as a filler in non cementitious materials to give them a rheology similar to cementitious products. Wollastonite acts as a reinforcement material, improving the mechanical properties of construction materials.
Plastics and Polymers:
In the plastics and polymer industry, wollastonite serves as a reinforcing filler. Its fibrous structure enhances the tensile strength and dimensional stability of plastic products. Additionally, wollastonite is employed as a flame retardant, contributing to the reduction of fire hazards in plastic applications.
Paints and Coatings:
Wollastonite is utilised as a functional filler and pigment extender in paints and coatings. Its incorporation enhances the coating’s mechanical properties, such as hardness and abrasion resistance. Acts as a PH buffer , improves resistance to weathering, reduces gloss, reduces pigment consumption and acts as a flatting suspending agent. Moreover, wollastonite contributes to the reduction of production costs while maintaining or improving the quality of the end product.
Agriculture:
In agriculture, wollastonite acts as a soil conditioner. Its calcium and silicon content enhances soil structure and nutrient availability, promoting healthier plant growth. Wollastonite is particularly beneficial in acidic soils, helping to neutralise acidity and improve overall soil fertility.
With its diverse range of applications and valuable properties, wollastonite stands as a crucial component in multiple industries, contributing to the improvement of material performance and the overall efficiency of end products.