Quantifying the environmental impacts of braking emissions Ideal brake pad materials for a sustainable future

Abstract

This work compares particle emissions coming from three different brake pad materials in order to determine which material produces the least emissions, and two different braking cycles in order to analyze the effect of electri fication in the automotive industry on braking particle emissions due to regenerative braking. The targeted market for this research is the European market, and therefore Volvo's European brake pads (ECE) were treated as the baseline material tested with a gray cast iron brake disc and the WLTP (Worldwide Harmonized Light Duty Vehicles Test Procedure) braking cycle for ICE (internal combustion engine) vehicles. This test procedure was repeated for two other brake pads: non-asbestos organic (NAO) commonly used in USA and Asian markets, and a new composition of non-asbestos organic produced by Volvo's supplier (new NAO) to mitigate brake emissions. Then the test procedure was repeated for ECE brake pads with a modi fied WLTP braking cycle to simulate the decrease in magnitude of friction braking with an electric vehicle. Tests were done using a closed-chamber brake dynamometer and an electrostatic precipitator for particle mass and count measurements in real time. A membrane-type filter made by Pallflex was used for particle collection. This study found that a majority of the particles measured were less than 1µm in diameter (PM1), and that of the four experiments considered, ECE brake pads produce the most braking emissions in terms of both mass and count. The second highest quantity of emissions emitted came from the NAO brake pads in terms of both mass and count. Then, the new NAO pads and ECE pads with the EV braking cycle produced the least amount of emissions, new NAO producing the least emissions by mass, and ECE EV braking cycle producing the lease emissions by count.