ASTM D7867 Measurement of Rotational Viscosity of liquid

Scope:

ASTM D7867 is useful to get information about the extent of temperature dependence which in turn is important to prepare a viscosity-temperature table or curve. This information would allow a manufacturer or user to predict the impact of heating the paint.

Procedure:

Three test methods are described in ASTM D7867:

Test Method A is performed with a viscometer that has a concentric (coaxial) cylinder capability, with specimen sizes (2 to 20 mL). At low to medium shear rates, this test determines apparent viscosity as a function of temperature. Test Method B is performed with a viscometer that has cone/plate test geometry. In comparison to Method A, the smaller specimen size allows for better temperature control and rapid analysis of the viscosity-temperature profile. Test Method C is run either with coaxial cylinder geometry or cone/plate geometry. A shear rate ramp is done at a discreet temperature and the viscosity values are recorded.

Video 01: Viscosity measurement using an Ostwald’s viscometer

Specimen size:

Temperature control for test methods A, B, and C are required to be set at ±0.2 °C most preferably within ±0.1 °C.

Data

In ASTM D7867, the viscosity is calculated as follows,

Where,

F is force

 μ is the viscosity of the fluid

A is the area of each plate

u/y   is the rate of shear deformation

Conclusion:

ASTM D7867 is useful to get information about the extent of temperature dependence which in turn is important to prepare a viscosity-temperature table or curve.