Clay was intercalated and exfoliated by neutralized dimethylol butanoic acid (DMBA) and used to fabricate rigid polyurethane foam (RPUF)/clay nanocomposites. Cream time, gel time, and tack-free time increased with the addition and increasing amount of clay whereas foam density and compression strength decreased. Cell size, closed cell content, volume change upon heating and cooling, and thermal conductivity of the foam decreased with the addition and increasing amount of clay with a minimum at 2 pphp (parts per 100 polyol by weight). The glass transition and decomposition temperatures increased with increasing clay content due to the restricted motion of chains and barrier property of the clay platelets. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 1992-1997, 2010