Evaluation of a Low-Metals, Non-Petrochemical Coke for Use in Automotive Friction Materials (SAE Paper 2020-01-1603)

A study was performed to compare the performance of small and large automotive, semi-metallic, friction pads, each manufactured with one of two different calcined coke fillers. Coke #1 is a conventional calcined petroleum coke, and Coke #2 a proprietary, calcined coke manufactured from a non-petrochemical feedstock and sold by Asbury Carbons under the trade name "EcoGreen". The subject coke materials were fully characterized, physically and chemically. Chemical characterization included a modified TCLP leaching study performed on each coke. Both coke materials are similar in their respective physical properties, including morphology, hardness, and crush strength. However, there is a significant difference in the trace metal content of the two materials, with Coke #1 containing a higher content of sulfur, calcium, iron, nickel, and vanadium than Coke #2. Nickel, vanadium, and sulfur are considered potential environmentally hazardous substances. Initial friction element evaluation was performed using the J661 Brake Lining Quality Test Procedure (Chase Test). Based on Chase test qualification, complete inertial dynamometer testing (SAE J2522) was also performed. Each coke material was formulated into two different automotive brake elements: a small vehicle pad with a Toyota rotor, and a large vehicle pad using an AC Delco rotor. The friction formula utilized is a commercial, proprietary mixture. Test results show that the friction materials, each containing one of the subject coke fillers, behaved similarly. Overall, test results indicate that road testing and further evaluation of Coke #2, an environmentally sustainable, low metals and low sulfur coke, by friction manufacturers is warranted.