Clam shell waste as a filler ingredient for sustainable brake pad friction materials

Waste clam shell was evaluated as an eco-friendly filler ingredient for brake friction materials and was compared with standard filler, like calcite and barite. The raw shell crystalline structure, morphology, and thermal stability were characterized. It was subsequently milled to 25–45 μm and incorporated into brake pad formulations in concentrations of 15 wt% and 30 wt%. Pin-on-disc tests at room temperature, 200 °C, and 400 °C under mild wear conditions were conducted. Seashell and calcite obtained coefficient of friction (CoF) similar to barite at room temperature and at 200 °C. At 400 °C, 15 wt% seashell or calcite reduced the CoF with respect to barite, whereas 30 wt% increased the CoF. Wear coefficients increased with temperature. Samples containing only barite showed the lowest wear at room temperature. On the other hand, at 400 °C samples with 15 wt% seashell or calcite showed the lowest wear, with seashell being equivalent to calcite and outperforming barite. Seashell and calcite formed a protective tribofilm on the disc at elevated temperature, which reduced disc wear. The emissions were found to be proportional to the wear of the samples. Life cycle assessment showed that replacing calcite for seashell reduces the environmental impact over all categories. Overall, seashell powder had comparable performance to calcite and barite, and 15 wt% seashell offered the best balance between friction stability, wear resistance, and emissions. This highlights the potential of seashell waste as a sustainable filler in friction materials. • An eco-friendly brake friction material with waste seashell was developed. • Seashell is composed of calcium carbonate in the form of aragonite. • Seashell had similar wear and friction performance as standard calcium carbonate. • Seashell at a content of 15 % had less emissions then standard calcium carbonate. • Seashell waste showed great potential as filler ingredient in brake materials.