APPARENT VISCOSITY BY CAPILLARY VISCOMETER AT HIGH TEMPERATURE HIGH SHEAR: D4683
TEST SUMMARY
This test method covers the laboratory determination of the viscosity of engine oils at 150° C and 1 x 10(6) s(-1) shear rate using a tapered bearing simulator-viscometer (TBS Viscometer) equipped with a refined thermoregulator system. Older TBS units not so equipped must use Test Method D4683-87.
The Newtonian calibration oils used to establish this test method cover the range from approximately 1.5 to 5.6 cP mPa• s at 150° C. The non-Newtonian reference oil used to establish this test method has a viscosity of approximately 3.5 cP mPa• s at 150° C and a shear rate of 1 x 10(6) s(-1).
Applicability to petroleum products other than engine oils has not been determined in preparing this test method.
A motor drives a tapered rotor that is closely fitted inside a matched stator. The rotor exhibits a reactive torque response when it encounters a viscous resistance from an oil that fills the gap between the rotor and stator. Two oils, a calibration oil and non-Newtonian reference oil, are used to determine the gap distance between the rotor and stator so that a shear rate of 1 x 10(6) s(-1) is maintained. Additional calibration oils are used to establish the viscosity/torque relationship that is required for the determination of the apparent viscosity of test oils at 150° C.
