I would like to check the viscosity for my CNC suspension; however, I have no idea how to select the viscometer.
1. Follow with TAPPI T230om8 for cellulose, Cannon-Fenske viscometer is suggested but I found some research group use Ostwald Viscometer for CNC. Which one is the best for CNC ?
2. Because the viscosity value of CNC is smaller than wood fiber, so, what size of viscometer I should use ? TAPPI said, "to avoid the error, 100-300s is suggested", but it is based on general cellulose. However, I think CNC would give lower than 100s (approximately about 25-50s). Does the error can be minimized with the 25-50s tube ?
If anyone have experience on this kind of experiment, kindly suggest me.
Nattinee,
the right solvent flow time depends on what concentration of CNC you have. However, the type of viscometer does not matter. If you only have low concentrations of CNC, you need to use a viscometer that gives a decent flow time for water. To roughly calculate the flow time, use the Quemada equation for the viscosity of suspensions. This gives relative viscosity as (1-phi/phimax)^-2. With phi the volume fraction of CNC and phimax the fraction of CNC at which the viscosity diverges. Take 0.63 as a first approximation. Using these numbers: with 10% (=0.1) volume fraction, you'll have a viscosity only 50% higher than water.
The right flow time depends on how accurate you want your results to be. Clearly, "Fast" tubes and low viscosities will give low accuracy.
viscosity is variable parameter, solvent, stress, rate, torque, temperature..........
u have four chance depends on money u have
1) kinematic viscometer (manuel like oswald),
2) viscometer with spindle (i prefer you take many spindle has wide meas. range
3) rheometer (applied stress at varios shear rate on sample with cones or plates and give viscoelastic properties according to yield stress point)
4) rheometer with oscillatory, u can determine whether sample has storage and loss modulus properties that is viscoelastic properties easily.
In nanocellulose, viscoelastic parameters is great important
For example we are using rheometer with without oscillatory during nanofibril and crystal measurements, yet we need oscillatory.
good luck
Thank you everyone for your suggestion. I can gain lots of knowledge from your helpful answer. I will check my condition and select the possible technique.
By the way, thank your so much, Alan Parker. Your answer is really clear my point.
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