Ethanolamine and L‐arginine treated wood flour were added to polyvinyl chloride (PVC) in order to improve the interphase between PVC and wood. The influence of the treatment on pH‐value changes and nitrogen fixation of the wood and mechanical properties of the composite were evaluated. The treatments changed the pH of wood from acidic to basic. The highest nitrogen fixation was measured for monoethanolamine and L‐arginine treated wood flour at high concentrations. Tensile strength, elongation at break, and unnotched impact strength were improved by ethanolamine and L‐arginine treatments considerably. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011