Polyurethanes are synthesized using three different hydroxyalkylated cardanol-formaldehyde resins, diphenylmethane diisocyanate (MDI), and a commercial polyol (PPG-2000). These polyurethanes are found to be tough and crosslinked. A polyurethane prepared using a higher mole ratio of cardanol/formaldehyde of hydroxyalkylated cardanol-formaldehyde resin is found to possess better thermal and mechanical properties than the polyurethane prepared from a lower mole ratio. (c) 2005 Wiley Periodicals, Inc.