Binary blends of poly (vinyl chloride) (PVC) and the maleic anhydride-allyl propionate (MA-AP) copolymer have been prepared in tetrahydrofurane solution, aimed the improvement of the thermomechanical properties. The blends in the form of films were studied using thermomechanical analyzer (TMA). The glass transition temperatures (T-g), thermal expansion coefficient (alpha) and other thermomechanical data for the blends were calculated. Consequently, according to increase in ratio of the MA-AP copolymer in the mixture, the MA-AP copolymer has a plasticing affect on the PVC. (C) 2004 Elsevier B.V. All rights reserved.