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Modern organic bonded friction linings contain both tin-(II)-sulfide and tin-(IV)-sulfide as solid lubricants. Due to their chemical and physical properties tin sulfides act as friction stabilizers and improve wear of disc and pad or lining not only in low steel and non-steel formulations but also in semimetallics.
The influence of the particle size distribution in disc brake pads was investigated systematically. In the first run different particle size grades of tin sulfides were prepared: large particle, technical, fine and super fine grade.
The medium diameter (D 50), surface and sieve residues were determined by using international standard testing methods. The thermal properties of the pure grades were investigated by DSC/TGA showing that the particle size distribution influences oxidation kinetics. The decomposition behavior was determined in inert atmosphere applying the same measurement system.
To complete these data samples of tin sulfides were treated in an oven under air atmosphere up to 500°C to analyze the chemical composition of the oxidation products.
All grades were added in same amounts to a modern NAO formulation and tested on a dynamometer applying a standard program under various speeds and brake pressures.
The friction levels and wear characteristics were put into correlation with the designed particle grades.