In order to decrease moisture uptake and hence provide rigidity and dimensional stability in a nylon-6 block copolymer (NBC), powdered phenolic resin was incorporated into the formulation as a filler and processed by reaction injection molding. A novolac resin was cured with hexamethylenetetramine to produce the phenolic resin, which was modified with diethylamine in order to remplaced the -OH groups by diethylamine groups. 5% by weight of modified and unmodified powdered phenolic resin was used as a filler in the nylon-6 block copolymers, and reinforced-nylon-6 block copolymer plaques were produced by reaction injection molding at 145 degrees C. The materials were characterized by dynamic mechanical thermal analysis (DMTA), and their flexural modulus, impact test, and dimensional stability were evaluated. In unmodified phenolic-resin-reinforced nylon-6 block copolymer, water absorption was decreased by 90% compared with the NBC without filler. Two mechanisms of interaction between the NBC and the phenolic resin have been proposed.