In this study, organic vapor sorption properties of different polypropylene (PP) forms (resin, sheet, thermoformed sheet, and atactic PP) at 25 degrees C were investigated. The sorption of benzaldehyde at five vapor activities was studied by using a continuous gravimetric method. The sorption of benzaldehyde vapor in PP exhibited different behaviors among resin, sheet, and polyhedron thermoformed sheet. The experimental results demonstrated that the extrusion and thermoforming processes used for forming these parts had a great impact on the sorption behavior because of the changes in surface and bulk morphologies, especially at high vapor activities. (C) 2008 Wiley Periodicals, Inc.