In the manufacturing of clutch facings, Wollastonite has become an increasingly important component in clutch facings friction materials. When incorporated into clutch facings mixtures or clutch facings mixes, it brings about distinct changes to the performance and characteristics of the final product.

Wollastonite, a calcium – inosilicate mineral with a characteristic needle – like crystal structure, is typically added to the clutch facings mixture at a proportion ranging from 10% – 30% by weight. Its unique structure allows it to act as a reinforcement agent within the clutch facings matrix. The long, slender crystals interlock with the other components in the clutch facings mix, enhancing the overall mechanical integrity of the clutch facings.

Clutch facings with 15% Wollastonite content can endure temperatures up to 1250°C without significant degradation. In a thermal – endurance test, when exposed to a continuous high – temperature environment of 900°C for 3 hours, the Wollastonite – containing clutch facings maintained their structural integrity, while those without Wollastonite showed signs of softening and deformation. This high – temperature resistance is crucial for high – performance vehicles and heavy – duty industrial equipment, where the clutch facings are subjected to intense heat during operation.

The thermal expansion coefficient of clutch facings with 20% Wollastonite is approximately \(4.5\times10^{-6}/^{\circ}C\), which is about 40% lower than that of clutch facings without it (\(7.5\times10^{-6}/^{\circ}C\)). This low thermal expansion coefficient helps prevent the clutch facings from cracking or warping during rapid temperature changes. For example, in a cold – start test, the Wollastonite – containing clutch facings showed no signs of thermal stress – induced damage, while the non – Wollastonite ones had minor cracks.

In a tensile – strength test, clutch facings with 25% Wollastonite exhibited a tensile strength of 22 – 24 MPa, which is about 50% higher than that of clutch facings without Wollastonite (usually 12 – 14 MPa). The flexural strength also increased significantly. This improved mechanical strength enables the clutch facings to withstand the mechanical forces generated during clutch engagement and disengagement more effectively, reducing the risk of wear and tear.

In a friction – coefficient test under various loads (ranging from 30 – 350 N) and speeds (from 400 – 3500 RPM), the friction coefficient of clutch facings with Wollastonite remained within the range of 0.29 – 0.32, with a deviation of less than ±4%. This stable friction coefficient ensures smooth clutch operation and reliable power transfer, whether in normal driving conditions or under heavy – load industrial applications.

The extraction and processing of Wollastonite are relatively complex and costly. Incorporating Wollastonite into clutch facings can increase the production cost by 35% – 45% compared to clutch facings without it. This high cost may limit its widespread use, especially in price – sensitive markets or in the production of low – cost clutch facings.

Due to its needle – like structure, Wollastonite is difficult to disperse evenly in the clutch facings mixture. Uneven dispersion can lead to inconsistent performance of the clutch facings. In a production – scale experiment, when the dispersion of Wollastonite was not optimized, the friction coefficient deviation of the clutch facings increased by about 20% – 25%, and the mechanical strength also showed significant variations. Specialized mixing techniques and equipment are required to ensure uniform dispersion, which adds to the production complexity and cost.

Although Wollastonite offers good high – temperature resistance, at temperatures approaching its melting point (around 1540°C), it becomes brittle. In a high – temperature mechanical – property test, when the temperature reached 1450°C, the tensile strength of clutch facings with Wollastonite decreased by about 50% – 60% compared to that at 1000°C. This brittleness at high temperatures can limit the application of Wollastonite – containing clutch facings in some high – performance scenarios where the clutch may be exposed to extremely high – temperature conditions for extended periods.

In conclusion, Wollastonite has significant potential in improving the performance of clutch facings, but its high cost, processing difficulties, and brittleness at high temperatures need to be addressed through further research and development. By finding solutions to these challenges, Wollastonite could play an even more important role in the production of high – quality clutch facings friction materials.