Poly(vinyl chloride)/chlorinated polyethylene (PVC/CPE)/methylacryloylpropyl-containing polyhedral oligomeric silsesquioxane (MAPPOSS) nanocomposites are prepared. The plastic behavior and dynamic rheological behavior of PVC/CPE/MAPPOSS are investigated. The influences of composition on dynamic storage modulus G, loss modulus G, and complex viscosity * of PVC/CPE/MAPPOSS melts are discussed. The dynamic mechanical properties, mechanical properties, and morphology are determined. The results show that both plastic time and balance torque of the nanocomposites decrease, but the G, G, and * all increase with increasing MAPPOSS content. The maximum value of the dynamic mechanical loss tan decreases and elasticity increases when MAPPOSS is added. The impact strength of the nanocomposites increases with increasing MAPPOSS content and has the best value at 10% content of MAPPOSS, which is 5.38 kJ/m2 higher than that of the blend without MAPPOSS. The MAPPOSS can be used as an efficient process aid and impact aid for the PVC/CPE blend. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013