Viscosity Measurements of Dilute Aqueous Suspensions of Cellulose Nanocrystals by Rolling Ball Viscometer Method (CAT#: STEM-VTT-0008-ZJF)

The rolling ball measurement is based on Stokes’s Law, as influenced by the angle of inclination of the tube (or capillary). Determine the viscosity of a liquid by observing the rolling time of a solid sphere (ball) under the influence of gravity in an inclined cylindrical tube filled with the sample liquid. Measure the time taken by the ball to travel the fixed distance between two ring marks or measuring sensors. For each single measured rolling time, the resulting viscosity can be expressed as dynamic viscosity (mPa · s) as well as kinematic viscosity (mm2 /s) for a sample of known density.

Cellulose, Non-Newtonian Fluid Mechanics

1. Select a measuring system within the anticipated range of viscosity of the sample liquid. As necessary, heat the clean and dry tube and ball of the viscometer to the temperature specified in the individual monograph, and control the temperature to ±0.1°. Select a measuring angle to obtain a minimum rolling time of 20 s.
2. Fill the tube with the sample liquid, being careful to avoid bubble formation. Close the tube, and insert it in the instrument. Allow to equilibrate at the specified temperature for NLT 15 min for a rolling ball viscometer with a tube of large diameter. For a micro rolling ball viscometer, follow the instrument manufacturer’s instructions regarding temperature equilibration.
3. Release the ball, and record the time required for the ball to roll from the upper to the lower ring mark (or measuring sensor). Repeat the test run at least four times. The rolling time in the fluid under examination is the mean of NLT four consecutive determinations. The result is valid if the percent relative standard deviation (%RSD) for the four readings is NMT 2.0%.
4. Calculate the Newtonian viscosity η, in mPa·s

• Rolling ball viscometer: Usually consists of a tube (or capillary) that contains the sample liquid under test and a ball chosen so that it will require a minimum rolling time of 20 s at the measuring angle in the ample liquid.
• Sample liquid