Methods for Assessing the Water Dispersibility of Titanium Dioxide
1. Simple method
Take a 500ml transparent glass beaker, fill with water, take 5g of titanium dioxide in it with a small spoon, stir with a glass rod for 10 minutes and let it stand. Then observe the settling of the titanium dioxide, the faster the settling (layering), the worse the water dispersion, on the other hand, the slower the settling (layering), the better the water dispersion.
2. Standard method: Water dispersibility determination procedure
1. Weighing
Weigh 15g of titanium dioxide into a 500ml beaker with 285ml of deionised water.
2. Dispersion
Place the beaker on a magnetic stirrer and stir for 30 minutes.
3. Determination of the starting slurry
Immediately take 10ml of the shaken slurry and put it into a constant weight evaporation dish, weigh the slurry (W1), then put it into an oven at 140°C for more than 4 hours to reach a constant weight, cool it down and weigh the residual portion (W2).
4. Settling
Fill the remaining dispersion into a measuring cylinder, keep the liquid level at 200mm, place on a flat table and leave to settle for 5 hours.
5. Dispersion sampling
Using a pipette, draw the settled dispersion into a 250 ml beaker from the level to the bottom 30 mm (do not shake the measuring cylinder).
6. Drying and weighing of the dispersion
Use a pipette to draw 10 ml of the shaken dispersion from the 250 ml beaker into a constant weight evaporation dish, at which point the slurry is weighed (W3).
Bake as above for 4 hours or more, cool and weigh the residual portion (W4).
7. Calculation: W4 x W1
Water dispersibility (%) = ---- × 100
W2 × W3
Where: W1: weight of 10ml of initial slurry before standing
W2: Content of titanium dioxide in W1
W3: weight of the slurry after 5 hours of standing
W4: Content of titanium dioxide in W3
