Evaluation of High Viscosity of Solidified Lubricants at High Pressure by Rayleigh Light Scattering and Photon Correlation Technique

A new viscosity measuring system was designed and set up employing Rayleigh light scattering and the photon correlation technique in which a high-pressure diamond-anvil cell (DAC) was used. Two kinds of experiments were conducted. One was the measurement of a dilute suspension of polystyrene latex spheres in liquid lubricant and W/O emulsion. Correlation functions induced by the Brownian motion of fine spheres in the lubricant were observed and the viscosities were obtained, the measurement time of which was one-tenth shorter than that of the falling-body method. The other experiment was the measurement of 5P4E (polyphenyl ether) and DOP (dioctylphthalate) without mixing polystyrene spheres. Very weak but observable correlation functions related to structural relaxation were observed and the viscosities of solidified lubricants (about 10⁹ Pa·s), obtained in a very short time by introducing a shift factor for relaxation time, were consistent with those extrapolated from data obtained using the falling-body method.