The development of high performance products at lowest possible product development-time and costs is the demand of the plastics industry today. A successful use of process simulation to describe the behavior of complex structures and to minimize the technical and economic risks for companies requires application and process-relevant material data. The pvT-behavior of polymers is an essential parameter for process simulations. Especially the dependence of the specific volume of pressure and temperature under process conditions is not mapped to the existing measurement methods. In this study pvT measurements were performed on selected commercial amorphous polymers (PC, ABS) with a Pirouette pvT device, a combination of a dilatometer and Couette rheometer. The specific volume was determined as a function of temperature (25-300°C) and at pressures ranging between 200-1000 bar. On top of that, the influence of the cooling rate was also investigated by pvT measurements performed at cooling rates of 0.1°C/s, 1°C/s and 100°C/s. The results of the experiments show non expected pvT behavior as an increase of volume was found in the area of the glass transition temperature for all cooling rates and pressure steps applied. The results were confirmed for the low cooling rates with a second method. These results could be an explanation route for several problems reported by industry where huge gaps between simulation results and processing behavior exist.