Method for making a friction material, in particular for making brake pads and relative brake pads

A method for making a braking element, including the following steps:

• a) forming a geopolymeric solution by mixing an aluminosilicate source with an alkaline silicate solution;
• b) obtaining a slurry by adding a friction mix to the formed geopolymeric solution from the previous mixing step, wherein the geopolymeric solution is a binder for the friction mix;
• c) casting the slurry in a mold without pressure at a temperature between room temperature and 120° C., and maintaining the slurry inside the hot mold for a time comprised between 5 minutes and 2 hours until the slurry is substantially solidified;
• d) demolding the solidified slurry to obtain a pad or block of solid friction material;
• e) attaching a backplate to the pad or block of solid friction material, wherein the step of attaching is carried out:
• i) either as a consequence of the casting step, having been provided the backplate within the mold, or
• ii) after the pad or block of solid friction material is demolded;
• f) curing for a time between 1 and 24 hours and at a temperature of between 60° C. and 120° C. the pad or block of solid friction material having the backplate attached to it;
• and wherein
• g) the aluminosilicate source and the alkaline silicate in step a) are chosen so that a SiO2/Al2O3 molar ratio in the solid friction material is between 3 and 5;
• h) the alkaline silicate solution in step a) is chosen so that a SiO2/R2O molar ratio in the solid friction material is between 0.7 and 1.5, and wherein R is chosen among Na, K, and Li;
• and
• i) the binder formed by the geopolymeric solution is present in the slurry in a quantity equal to or greater than 30% by volume based on the total volume of the slurry.