Crumbed rubber wastes (1 to 60% by wt.) were used for manufg. polyurethane-matrix composites. The wastes were added to the urethane pre-polymers synthesized of diisocynate and polyester polyol (Poles 55/20) at 80 degrees C and stirred for 1-2 min. Butylene glycol was used as a chain extender. The reaction was initiated with diazabicyclo[2.2.2]octane. The composites contg. 1-5% of the rubber waste and heated for 8 h showed the best mech. properties.