Fig 4a Dispersion rate related t) surfactant No.l
Fig 4b Dispersion rate related t) surfactant No.2
4.1 Droplet sizes of the emulsified oil in the water
It has been understood that the higher the stability rate of a dispersant the higher
the dispersing ability of it is as mentioned in section 3. Distribution of the droplet
numbers and of droplet weights in the layer of the emulsified oil over the surfactant N0.1
and N0.2 were investigated. The viscosity of the oil used was 20,000cSt at 21'C. The
solvent used was solventD. The measurements on the droplets sizes were conducted after a
settling time of 20 minutes.
A Coulter counter, which adopts electric resistance via the Coulter Principle, was used
in the measurements.
The result of the measurements are shown in Table 6a, 6b and Fig. 5a, 5b. In Table 6a,
droplet sizes of oil emulsified by surfactant N0.1 ranged from 2.01~4.02 ,L m to 26.1~28.2μ
m. Droplets of 2.01~4.02 μm composed the largest group of 68.796 , and the group of
4.02~6.04 /L m was second largest, which made up 19.996 . These two groups of droplets
together made up 88.6%. Meanwhile, in Table 6b, droplet sizes of oil emulsified by the
surfactant N0.2 ranged from 2.01~4.02 ,x m to 16.1~18.1 /x m. The droplet sizes of
2.01~4.02 Ix m made up the largest group of 84.396, and the group of 4.02~6.04 /~ m was
thc second largest, which made up 13.496. These two groups of droplets made up 97.796 of
the total numbers.
This is believed to be because larger droplets of oil
emulsified in the water right after agitation have a strong tendency to resurface in
the water, cohering with each other, growing larger in occurrence of coalescence.
The resurfacing rate of oil droplets determined by Stokes' Law is shown in the
following table.
| droplet size(microns) |
resurfacing rate(mm/10minutes) |
| 2.07 |
0.43 |
| 2.12 |
4.50 |
| 3.02 |
10.44 |
| 4.63 |
21.60 |
In comparison of a resurfacing rate of 2.07-/t. m droplet to that of a 46.3-,4 m
droplet shows that the resurfacing rate of the larger one is about fifty times faster than
the smaller one. The droplet size of oil emulsified by an ineffective dispersant are apt
to be larger and the dispersion rate of the dispersant would turn out to be much lower.
Droplet group with the maximum distribution of oil weights was 4.02~6.04 ~c m, made up
19.3% of the total in Table 6a, while droplet group with maximum distribution of oil
weights was 2.01~4.02 ,1 m, made up 43.0% of the total in Table 6b. This result shows that
droplet range by the surfactant N0.2 with a low dispersion rate is smaller than droplet
range by N0.1. The number of droplets of the group of 2.01~4.02 Il m by N0.2 is more than
that the number of droplets of the same group by No.1.
Table 6a The measurement of droplets size after a settling time to 20
min. (Surfactant No.1 with Solvent D )
| Droplet size μm |
Weight distribution |
Distribution of droplet |
| % |
% |
Number |
| 0.00-2.01 |
0.0 |
0.0 |
0 |
| 2.01-4.02 |
13.2 |
68.7 |
34394 |
| 4.02-6.04 |
19.3 |
19.9 |
9947 |
| 6.04-8.05 |
18.9 |
6.9 |
3445 |
| 8.05-10.0 |
15.6 |
2.6 |
1283 |
| 10.0-12.0 |
12.4 |
1.1 |
547 |
| 12.0-14.1 |
8.3 |
0.4 |
221 |
| 14.1-16.1 |
6.1 |
0.2 |
106 |
| 16.1-18.1 |
3.2 |
0.2 |
37 |
| 18.1-20.1 |
1.4 |
0.0 |
12 |
| 20.1-22.1 |
0.8 |
0.0 |
5 |
| 22.1-24.1 |
0.2 |
0.0 |
1 |
| 24.1-26.1 |
0.3 |
0.0 |
1 |
| 26.1-28.2 |
0.3 |
0.0 |
1 |
| 計 |
100 |
100 |
50,000 |
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