Brake linings are vital components within vehicle braking systems, playing a crucial role in ensuring safe and efficient braking. The materials used in brake linings friction materials need to possess specific properties. Wollastonite, a naturally occurring mineral, features distinct needle – like or fibrous crystal structures. These unique physical structures endow wollastonite with excellent mechanical and thermal properties, making it a suitable candidate for use in the production of brake linings mixtures.

Wollastonite’s fibrous morphology is key to maintaining stable friction coefficients in brake linings friction materials. Its long, thin fibers can enhance the frictional contact area between the brake lining and the brake disc. During braking, the aspect ratio of wollastonite fibers, typically ranging from 10:1 to 30:1, helps to distribute the frictional forces evenly. This ensures that the friction coefficient remains relatively constant across different braking conditions, such as high – speed braking (above 100 km/h) or repeated braking cycles (up to 1000 consecutive braking operations in laboratory tests). As a result, the brake linings can adapt well to various driving scenarios, guaranteeing smooth and safe vehicle stops.

The high – strength nature of wollastonite significantly improves the wear resistance of brake linings. Its Mohs hardness, which is around 4.5 – 5.5, provides robust mechanical support to the brake lining matrix. Additionally, its stable physical properties under the high – temperature and high – stress conditions during braking operations reduce the wear rate. Laboratory wear tests have shown that brake linings containing 10 – 20% wollastonite by weight have a wear rate that is 30 – 50% lower than those without wollastonite. This leads to a longer service life, reducing the frequency of brake lining replacements and enhancing the overall reliability of the braking system.

Wollastonite has remarkable heat – resistant properties. It can endure high temperatures before softening or deforming. When brakes are applied and a large amount of heat is generated due to friction, wollastonite’s relatively high thermal conductivity helps to dissipate heat effectively. This heat – resistance property prevents the brake linings from rapid degradation under high – temperature conditions. For example, in fade tests where the brake linings are subjected to continuous high – energy braking, the temperature of the brake linings with wollastonite can be maintained 50 – 100°C lower than those without it, thus maintaining their braking performance.

Wollastonite is relatively abundant in nature, and its extraction and processing costs are relatively low. In the market, wollastonite prices are generally 30 – 50% lower than some high – performance synthetic friction – enhancing materials. Incorporating it into brake linings mixes can reduce the overall production cost of brake linings by 10 – 20% without sacrificing much in terms of performance. This makes it an attractive option for manufacturers aiming to balance quality and cost.

There may be compatibility problems when wollastonite is mixed with other components in the brake linings mixture. Some organic binders, such as phenolic resins commonly used in brake linings, may not interact well with wollastonite due to differences in their physical structures. This can lead to poor wetting and dispersion of wollastonite in the binder matrix. In addition, some friction – modifying additives may react with the surface of wollastonite under high – temperature conditions in the brake lining, forming unwanted substances that could potentially affect the overall performance of the brake linings.

Although wollastonite has many advantages, in some high – performance braking applications, such as in high – speed racing cars or heavy – duty industrial machinery, its performance may not be sufficient. High – speed racing cars require brake linings to withstand extremely high – energy braking, with braking forces capable of decelerating the vehicle from 300 km/h to a complete stop within a few seconds. In such cases, the friction and heat – dissipation requirements are much higher than normal vehicles. Wollastonite – based brake linings may not be able to meet these extreme requirements as well as some advanced ceramic – based or carbon – based friction materials.

During the wear process of brake linings containing wollastonite, there may be a certain amount of dust emission. The fine – grained wollastonite particles, with an average particle size of 5 – 10 μm in the worn – out dust, can be easily suspended in the air. These particles may not only cause environmental pollution but also pose a potential health risk if inhaled, as they can penetrate deep into the respiratory system. Stringent environmental and health regulations, such as the European Union’s particulate matter emission standards for vehicles, may limit the use of wollastonite – based brake linings in some areas.

Wollastonite offers several advantages such as friction stability, wear resistance, heat resistance, and cost – effectiveness when used in the production of brake linings. However, it also has some limitations including compatibility issues, limited applicability in high – performance scenarios, and dust emission problems. With continuous research and development, efforts are being made to address these disadvantages, such as surface – treating wollastonite to improve compatibility and developing dust – suppression technologies. These efforts aim to further optimize the use of wollastonite in brake linings to make braking systems more efficient and environmentally friendly.