Scope:

ASTM D4878 test is appropriate in research work or quality control specifications testing. The viscosity of a fluid is defined as its resistance to a uniformly continuous flow without turbulence or other influences.

Procedure

In ASTM D4878, enough sample is first placed in the smallest container to cover the immersion mark on the viscometer spindle and submerged in a constant temperature bath to the sample level. Samples are stirred occasionally to avoid trapping air bubbles and the temperature is checked at different places within the container to verify consistency. Viscometer spindle is immersed into a sample to the immersion line. Viscosity of the sample is tested  using a 15-second rotation period. Spindles are cleaned after the analysis with a solvent appropriate for the polyol and equipment used, such as methanol or acetone.

Specimen Size

At 25°C, ASTM D4878 measures the viscosity of polyols in the range of 10 to 100 000 mPa.s (cP). The torque on a spindle revolving at constant speed in a liquid sample at 25 ± 0.1°C is used to determine the viscosity.

Data:

Using this equation the kinematic viscosity, v is determined using ASTM D4878:
V= C × t
Where:
V= kinematic viscosity, mm²/s
C=calibration constant of viscometer, (mm2/s)/s
t= mean flow time, s