Brake Pads Chopped Acrylic Fiber(PAN)
Chopped acrylic fiber derived from polyacrylonitrile (PAN) has become a critical reinforcing component in brake pad formulations, driven by the automotive industry’s demand for reliable friction materials that balance performance, durability, and environmental compatibility.
Material Characteristics and Core Properties
PAN-based chopped acrylic fiber, typically 1–6 mm in length, exhibits a unique combination of physical and chemical traits that make it suitable for brake pad applications. High thermal stability, a key attribute for materials exposed to the extreme temperatures (often exceeding 500°C) generated during braking, ensures the fiber retains structural integrity without significant degradation. Its inherent tensile strength enhances the mechanical robustness of the brake pad matrix, reducing the risk of crack formation under repeated thermal and mechanical stress. Additionally, the fiber’s compatibility with various resin binders—including phenol-formaldehyde resins, which are widely used in friction material manufacturing—facilitates uniform dispersion, a factor that directly impacts the consistency of friction performance across the pad’s service life. Unlike some synthetic fibers, PAN acrylic fiber also offers moderate absorbency, allowing it to interact effectively with other formulation components such as friction modifiers and abrasives, thereby optimizing the overall friction coefficient.
Role in Brake Pad Formulation
In brake pad composites, chopped PAN acrylic fiber serves dual roles: as a reinforcing agent and a friction regulator. By integrating into the matrix, the fiber creates a three-dimensional network that distributes stress evenly throughout the pad, mitigating wear and extending service life. This reinforcing effect is particularly pronounced in low-metallic and non-asbestos organic (NAO) brake pads, where synthetic fibers often replace traditional asbestos to meet environmental and safety regulations. The fiber also influences the friction behavior of the pad: when subjected to braking forces, it contributes to the formation of a stable friction film on the rotor surface, preventing excessive brake fade and ensuring consistent stopping power. In formulations developed by Annat Brake Pads Compounds, for instance, precise control of PAN acrylic fiber length and loading has been shown to enhance pad performance in both passenger vehicles and light commercial applications.
Formulation Considerations and Processing Parameters
The successful integration of chopped PAN acrylic fiber into brake pads requires careful attention to formulation ratios and processing conditions. Fiber loading, generally ranging from 2% to 8% by weight of the total formulation, must be balanced to avoid compromising other critical properties—excessive loading can increase brittleness, while insufficient loading fails to provide adequate reinforcement. Processing temperature and pressure during pad molding also play a pivotal role; improper curing conditions may lead to poor fiber-matrix adhesion, diminishing the fiber’s reinforcing effectiveness. Manufacturers often employ high-shear mixing to ensure uniform fiber dispersion, a step that is essential for maintaining consistent performance across production batches. It is worth noting that the fiber’s surface treatment, such as sizing with coupling agents, can further improve interfacial bonding with the resin matrix, enhancing the overall durability of the brake pad assemly.
Application-Specific Performance Advantages
PAN-based chopped acrylic fiber is particularly well-suited for passenger car and light truck brake pads, where smooth braking feel and low noise are as important as durability. In NAO formulations, it contributes to reduced rotor wear compared to metallic fibers, aligning with the industry’s trend toward longer-lasting, more environmentally friendly brake systems. Its resistance to chemical degradation from brake fluid and environmental contaminants ensures consistent performance over the pad’s service life. For heavy-duty applications, while not the primary reinforcing fiber, it can be blended with other high-performance fibers to optimize friction stability and mechanical strength, demonstrating its versatility across different brake pad categories.