Production of Brake Pads from Indigenous Materials

Abstract

This study investigated the potential of producing automobile disc brake pads in Ghana using environmentally friendly local materials, namely Periwinkle Shell Powder (PSP), Coconut Shell Ash (CSA), and kaolin (K), as alternatives to asbestos. Asbestos, widely used in the brake lining industry, was banned due to its carcinogenic properties. The properties of these base materials were characterised to determine their suitability as asbestos replacements. To create the brake lining samples, copper powder, zinc powder, aluminium powder, graphite, and epoxy resin binder were combined with the base materials. Two sets of samples were produced: one with PSP and CSA as the base material (PSP/CSA combination) and the other with PSP and kaolin (PSP/K combination). Different particle sizes (106 μm, 150 μm, 212 μm, and 300 μm) of the base materials were used, with 106 μm showing the best results. Brake pads were manufactured with a particle size of 106 μm using a mould designed to match the dimensions of a Toyota Camry saloon car, Model 2000. They were moulded at a pressure of approximately 50 bars, cured for 72 hours, and heat treated at 150 °C for 2 hours. Extensive tests were conducted to analyse the physical, mechanical, morphology, thermal, and tribological features of the brake linings. Commercial brake pads and an asbestos-based brake pad were used as controls for comparison. The results revealed that the bulk densities of the base materials (ranging from 0.833 g/cm3 to 1.718 g/cm3 ) were lower than that of asbestos (2.22 g/cm3 ), indicating that the materials would create lighter brake linings. The chemical and mineralogical compositions of the base materials were similar to those of asbestos, all containing SiO2, CaO, MgO, and Al2O3. The base materials exhibited similar thermal behaviour to asbestos, with peak degradation temperatures as follows: 745.88 °C for PS powder, 675.19 °C for CSA, 492.85 °C for kaolin, and approximately 688 °C for asbestos. The developed brake pads displayed favourable properties compared to asbestos-based and branded commercial brake pads. The PSP/CSA pad exhibited compressive strength and hardness values of 115.0 N/mm2 and 107.0 HBN, respectively, while the PSP/K pad had compressive and hardness values of 138.7 N/mm2 and 121 HBN, respectively — higher than those of the asbestos-based pad (110.0 N/mm2 and 101.0 HBN). The coefficient of friction for the developed pads ranged from 0.30 to 0.53, matching the asbestos-based pad. The average wear values of the PSP/CSA and PSP/K pads compared well with commercial and asbestos-based brake pads. Notably, the PS/K brake pad exhibited better wear performance with a value of 2.70 mg/m, compared to 3.80 mg/m for the asbestos-based pad. The developed pads demonstrated a density similar to that of the asbestos-based pad (1.890 g/cm3 ), with density values of 1.910 g/cm3 for the PSP/CSA pad and 2.160 g/cm3 for the PSP/K pad. Thermal analysis indicated that the developed pads could withstand high temperatures, decomposing only at temperatures close to 700 °C. Therefore, periwinkle shell powder, coconut shell ash, and kaolin can effectively serve as filler or reinforcement materials, replacing asbestos in automotive disc brake lining development. Brake pads produced using these materials performed satisfactorily, akin to asbestos-based pads along with other commercial brake pads in the market. It is recommended to exclusively produce the newly developed pads using a hot moulding process and thereafter reexamine their performance characteristics. Additionally, conducting longer-term on-road effectiveness and durability investigations will facilitate a comprehensive assessment of the composite linings.