Friction papers comprising PIPD fiber

A friction paper comprising:

• a) 40 to 70 parts by weight of a mixture of
• i) self bonding polypyridobisimidazole fiber, self bonding polypyridobisimidazole pulp, or mixtures thereof and wherein the self bonding is bonding between surfaces of pieces of the fiber and the pulp and
• ii) fiber selected from the group of para-aramid fiber, acrylic fiber, cellulose fiber, graphite fiber, glass fiber, metal fiber, ceramic fiber, vitreous fiber, and mixtures thereof;
• and
• b) 30 to 60 parts by weight of a material selected from the group of friction modifiers, structural resins, wet-strength resins, processing aids, fillers, and mixtures thereof;
• the parts by weight being based on the total amount of solids in a) and b) contained in the paper.