PVT stands for Pressure, Volume and Temperature. The specific volume can be described as a function of pressure and temperature. This material-specific relationship is a material property and can be measured with the PVT 500 according to ISO 17744.
The PVT 500 can measure both isothermal and isobaric. In an isothermal PVT measurement, the specific volume at constant temperature is determined as a function of pressure. In an isobaric measurement, the pressure is kept constant while the sample is typically cooled down and the resulting volume is measured.
The isobaric measurement process is therefore similar to the actual production process in injection molding and the generated data is especially relevant for the simulation of injection molding processes.
Especially knowledge of the shrinkage behavior is extremely important when designing molds. A PVT measurement also provides a precise description of the cooling process as it takes place in extrusion, for example.
The PVT 500 uses compressed air for cooling. Compared to the thermostats used previously, this allows higher temperatures of up to 500°C and cooling rates of up to 30 K/min. The PVT 500 can also be optionally operated with an external thermostat, for example to measure below room temperature.
The PVT 500 is operated via the Labrheo PC software. After defining the test parameters, the actual measurement is performed fully automatically by the software. During the measurement, the data can be monitored in real-time.
The evaluation is carried out with the PC software Winrheo 2. The generated data is displayed as a PVT diagram and can be parameterized with an integrated Tait-model. The Tait parameters can be entered directly into the common software used to simulate injection molding processes.
Optionally the PVT 500 can also be equipped to perform thermal conductivity measurements according to ASTM D5930 or ISO 22007.
The sensor for thermal conductivity is mounted just like a standard piston. The barrel is closed at the bottom during the test. The thermal conductivity measurement of solids or melt is performed under stationary conditions.
with external thermostat
This procedure is standardized in ISO 17744 for piston operated instruments. Isobaric PVT measurements are performed at constant pressure...
In isothermal PVT measurement, the measurement process starts at room temperature after the material is filled at melt temperature and...