Synergic effect of oxidized polyacrylonitrile fibers and zinc borate on spark suppression in automotive brake pad composite materials

Abstract

The mechanical, physical, and thermal properties of composite friction material are key parameters influencing both the direct performance of automotive brake systems and secondary phenomena, such as spark and flame generation during braking. These properties are strongly affected by the composition and interaction of the raw materials used in the formulation. In this study, a novel friction material for automotive brake pads was developed with the aim of improving tribological and physical performance while reducing spark and flame generation. Oxidized polyacrylonitrile (PAN) fiber was incorporated into a reference formulation at volume ratios of 1:1, 1:2, and 1:4 relative to the aramid fiber conventionally used. In addition, zinc borate was introduced at 5, 10, and 15 vol%, replacing part of the conventional filler content. A hybrid formulation containing both PAN fiber and zinc borate was also evaluated to investigate possible synergistic effects. The samples were characterized by scanning electron microscopy, Gogan hardness, specific gravity, cold and hot compressibility, and thermal conductivity tests. Spark and flame generation tests were also performed under simulated braking conditions. The results showed that the incorporation of PAN fiber reduced material stiffness, whereas zinc borate increased it; their combined use resulted in a more balanced mechanical response. Compressibility and porosity were also affected by the additives, with noticeable variations among the formulations. Internal shear strength was significantly influenced, with one hybrid formulation showing a marked increase. In particular, the hybrid formulation exhibited a balanced performance, with reduced spark generation, indicating its potential for automotive brake pad applications.