Development and characterization of green automotive brake pads from waste shells of giant African snail (Achatina achatina L.)

In this study, waste shells of African giant snail (Achatina achatina L.) were explored as candidates for asbestos-free non-carcinogenic brake pads. The results obtained showed that the density, Brinell hardness, and compressive strength of the snail shell (SS) brake pads were superior to the commercial sample used for comparison. These properties were found to decrease with increase in particle size, following a negative index power law model after the order of the Hall-Petch equation. However, the liquid absorption characteristics increased with increase in particle size and its model followed a positive index power law due to the pores in the matrix. On the other hand, the thermal conductivity showed no significant change with variation in particle size. The SS-based brake pad exhibited better frictional grip at the rubbing interfaces compared to the commercial brake pad sample. From the frictional results obtained, the commercial brake pad can be rated as Edge-Code-D whereas the frictional ratings for the SS-based brake pad with different particle sizes are Edge-Code-E (500μm and 250μm), Edge-Code-F (375μm), Edge-Code-G (125μm), and Edge-Code-H (90μm). The wear rates and wear areas of the developed SS-based brake pads were inferior to the commercial sample but can be improved by impregnating the matrix with more iron fillings to enhance the poor thermal conductivity and hence wear characteristics.