Conclusion
Measuring the specific volumes of polymers

Two techniques were presented for measuring the PvT of polymers. In the piston-cylinder technique, the polymer is directly compressed in a matrix. This technique is easy to set up and allows rapid temperature rises and falls. It is well-suited to simulating injection processes, but is not very credible for PvT measurements, especially when temperatures are rising. The piezometric device is perfectly hydrostatic, with very slow temperature and pressure rise and fall rates, so as to avoid temperature and pressure gradients within the sample; it provides accurate PvT measurements. On the other hand, even when automated, this device is very cumbersome to set up.

As most polymers are in a state of near thermodynamic equilibrium for most of their phase diagram, the only reliable data that can be used, for example, to simulate injection processes are experimental measurements...