Flake Graphite, a naturally – occurring form of carbon with a distinctive flake – like structure, has increasingly been incorporated into the production of brake shoes. When integrated into brake shoes mixtures and mixes, it significantly impacts the performance characteristics of brake shoes friction materials. Let’s delve into its technical parameters, advantages, and disadvantages.

Flake Graphite exhibits remarkable thermal conductivity, which can range from 100 – 300 W/(m·K) depending on its purity and processing. This high thermal conductivity is crucial for brake shoes as it enables efficient heat dissipation during the braking process. In a high – speed braking test, when the friction surface temperature of a brake shoe without flake graphite reached 400°C, the addition of 15% flake graphite by weight reduced the peak temperature to 300°C within 15 seconds.

It also has excellent electrical conductivity, with a resistivity typically in the range of \(10^{-4}-10^{-3}\Omega\cdot m\). This property can be beneficial in certain braking systems, especially those that require electrostatic discharge prevention during the braking process.

The aspect ratio of flake graphite, which is the ratio of its length to thickness, can be as high as 100 – 500. This high aspect ratio contributes to the reinforcement of the brake shoes friction materials. When added to the mixture, it can enhance the mechanical strength of the composite, improving its resistance to wear and tear.

One of the most significant advantages of using flake graphite in brake shoes is its outstanding heat – dissipation ability. Brake fade, a common issue caused by overheating during braking, is effectively mitigated. Tests have shown that brake shoes with flake graphite can maintain a stable friction coefficient of 0.35 – 0.45 even after 10 consecutive high – speed braking events, while those without it experienced a significant drop in the friction coefficient to 0.2 – 0.25 after 5 such events.

Graphite has natural self – lubricating properties. When flake graphite is added to the brake shoes friction materials, it can reduce the friction between the brake shoes and the brake disc. In a long – term wear test with 200,000 braking cycles, the wear volume of the brake shoes with flake graphite was only 3 – 4 cm³, while that of the non – graphite – containing brake shoes was 7 – 8 cm³. This represents a 40 – 50% reduction in wear, which not only extends the service life of the brake shoes but also reduces the frequency of brake disc replacement.

Flake graphite helps in maintaining a more stable friction coefficient over a wide range of temperatures. In a temperature – variable braking test from 50°C to 350°C, the friction coefficient of brake shoes with flake graphite fluctuated within a narrow range of ±0.05, while that of the control sample without it had a much larger fluctuation of ±0.15. This stable friction coefficient ensures a smooth and predictable braking experience for the driver.

The production and processing of high – quality flake graphite can be relatively expensive. Incorporating flake graphite into brake shoes can increase the production cost by 30 – 50% compared to traditional friction materials. This cost factor may limit its widespread use in mass – market brake shoes.

Ensuring uniform dispersion of flake graphite in the brake shoes mixture is a challenging task. Uneven dispersion can lead to inconsistent performance of the brake shoes. If the graphite flakes are concentrated in certain areas, those areas may experience excessive heat dissipation and low friction, while other areas may have poor heat dissipation and high wear.

Flake graphite is sensitive to contaminants. In harsh operating environments with dust, moisture, and chemicals, the performance of brake shoes with flake graphite may be degraded. For example, in a dusty environment, the friction coefficient of the brake shoes can be reduced by 10 – 20% due to the contamination of the graphite surface.

In conclusion, flake graphite offers excellent heat dissipation, self – lubricating properties, and friction stability in brake shoes production. However, its high cost, dispersion difficulties, and sensitivity to contamination need to be carefully addressed. Brake shoe manufacturers need to carefully evaluate these factors based on the specific requirements of their products and the target market.