What is the material of brake shoe friction pads?

What is the material of brake shoe friction pads?
Brake shoe friction lining materials mainly include asbestos resin (the use of which has been restricted by national regulations) type friction materials, non-asbestos resin type friction materials, metal fibre reinforced friction materials, semi-metallic fibre reinforced friction materials and mixed fibre reinforced friction materials.
Brake shoe friction lining:
1, the primary filter section filtration object is more than 5um suspended particles and more than 10um settling particles and all kinds of foreign matter. Tunnel fan can work continuously and effectively for 2 hours at 250°C. Any vehicle identification number (VIN) produced during the year is not allowed to be similar.
2. When the brake shoe friction linings are badly worn, or when the surface of the friction linings is seriously stained by oil or ablated, they should be replaced with new shoes. Replacement, the upper and lower wheels must be implemented at the same time, and must be selected from the same manufacturer, the same brand, similar material friction lining. Replacement of the new shoes. Piece and brake drum fit is not good, should be implemented grinding, until the requirements ;
3, most of the requirements are to ensure that the shoe and brake drum fit area is greater than 60% of the total area of the friction lining. Brake shoe return spring should be tested for its free length, if it exceeds 5% of its specification length, or when there is a gap between the circles, it should be replaced. If the brake shoes are warped, they will interfere with the bolts (nuts) of the brake gap adjustment device, and with the grooves of the piston of the brake parting pump and the grooves of the brake support plate. In this way, the brake shoe friction disc assembly will be free to open and return to the position.