The effect of adding rubber powder derived from waste tires to poplar wood particles on mechanical and water-resistant properties of particleboards was examined. Sixty panels were made with rubber contents of 0-40% at hot-pressing temperatures of 140-180 degrees C, methylene diphenyl diisocyanate resin contents of 2-6% and panel densities of 0.6 to 1 gcm(-3). Although the modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB) strength were reduced by adding rubber powder, the thickness swelling (TS) was reduced by 7.3-61% when 10-40% rubber powder was added. Four regression equations (rubber content, pressing temperature, resin content and target panel density as functions of MOR, MOE, IB and TS) were developed and a nonlinear programing model was derived with operation research theory to obtain the most desirable panel properties under some production constraints. (C) 2012 Published by Elsevier Ltd.