PURPOSE: To prepare abrasion-resistant powder which forms scarcely rusting friction materials when used in combination with fibrous substance and binder, by heat polymerizing a mixture of cashew nut shell liquid and an acid and adjusting the pH of the resultant polymer solution, followed by curing and crushing.

CONSTITUTION: A polymer solution obtained by heat polymerization of a mixture of cashew nut shell oil and an acid (e.g., sulfuric acid or a carboxylic acid) is adjusted to a pH of 6.0 or higher by the addition, of a base[e.g., NaOH or Ca(OH)2]. After addition of an aldehyde (e.g., paraformaldehyde), the polymer solution is heat cured and the cured product is crushed to obtain abrasion-resistant cashew dust. For preparation of friction materials, a mixture of fibrous substance (e.g., asbestos), the cashew dust and a binder (e.g., phenolic resin) is molded under heat and pressure.

EFFECT: The cashew dust produces friction materials which is free from sticking due to rust formation.