A Dynamic Bulk Modulus/PVT Apparatus for Characterization of Polymers

Currently, advanced tools for modeling injection modeling of thermoplastics and predicting formed part dimensional stability and residual stress content use the static bulk modulus of the polymer at the temperatures and pressures associated with the molding process. The short cycle times associated with injection molding, however, could be more accurately modeled if dynamic bulk modulus data were available. In addition, these data are critical for modeling of fracture and crack propagation in polymers, which forms the basis of strength and fracture analyses. Unfortunately, commercial equipment is not available for measuring dynamic bulk moduli. Therefore, development and design of a Dynamic Bulk Modulus/Pressure-Volume-Temperature (PVT) Apparatus will be addressed. The device would be used to measure the dynamic bulk modulus of polymers over a frequency range of 0.1-5000 Hz at pressures of 0-200 Mpa, and temperatures of 25-315C, as well as perform PVT measurements over the same temperature and pressure range. The apparatus will employ Terfenol-D, an advanced magnetostrictive material as the actuator used to oscillate the volume of a pressure vessel containing the sample and contrainment fluid. We anticipate a volumetric accuracy of 0.002 cm^3/gm.