Pressure Dependence of Bis(2-ethylhexyl) Sebacate and VG32 Hydraulic Oil Viscosities Using a Quartz Crystal Resonator

Abstract

Conductances versus sweep frequencies for AT-cut quartz crystal resonators have been measured for bis(2-ethylhexyl) sebacate and several machine oils under high pressure. The frequencies versus viscosities of these liquids appeared on the correlation line between frequency shift and viscosity. The correlation line agreement is essentially a criterion for when quartz resonators may be used because non-Newtonian silicone oils deviated from the correlation line. The responses of resonators immersed in bis(2-ethylhexyl) sebacate were obtained at pressures up to 350 MPa. Viscosities were calculated from the resonance frequencies. The pressure dependence of the bis(2-ethylhexyl) sebacate viscosity agreed well with that obtained with the rolling ball method. By using reference liquids, it was found that resonator responses were independent of temperature over the range 295–372 K. Viscosity measurements for VG32 hydraulic oil were taken at pressures up to 250 MPa and at the temperature at which the commercial viscosity grade was defined [313 K (40 °C)].