Scope:

ASTM D7109-12 test method for evaluating the shear stability of polymer-containing fluids determines the viscosity loss in mm²/s and percent. If the polymers are destroyed by mechanical stress, the viscosity of the fluid decreases. The loss in viscosity signifies a loss in shear stability as a result of polymer degradation. 

Test Procedure:

The test method consists of measuring the viscosity loss of the polymer-containing fluid at 100 °C by using a diesel injector apparatus. The procedure utilizes the European diesel injector test equipment. The test determines the loss in viscosity by running the 30 and 90 shearing cycles. A polymer-containing fluid is passed through a diesel injector nozzle. The shear rate at which the fluid is made to pass the nozzle, causes the polymer molecules to degrade. This degradation results in loss of kinematic viscosity of the fluid at test.

Specimen size:

Approximately 600 ml of test fluid is required per test.

Data:

The viscosity is reported in SI units.
Calculate the percent viscosity loss (PVL) of the sheared oil samples as follows:

where:
Vu = kinematic viscosity of unsheared oil at 100 °C, mm²/s,
V30 = kinematic viscosity of the 30 cycle sheared oil sample at 100 °C, mm²/s, and
V90 = kinematic viscosity of the 90 cycle sheared oil sample at 100 °C, mm²/s.