Difference between spreading coefficient and partition coefficient?
Answers
Answer:
Spreading coefficient, spreading parameter
The spreading coefficient or parameter is a measure of the tendency of a liquid phase tospread (complete wetting) on a second, liquid or solid phase.
Answer:
Explanation:Spreading Coefficient
The spreading coefficient is defined as the difference of the surface tension of the foaming medium
σ
f
, the surface tension of the defoamer
σ
d
, and the interfacial tension of both materials
σ
df
(13.4)
S
=
σ
f
-
σ
d
-
σ
df
.
It can be readily seen that the spreading coefficient
S
becomes increasingly positive as the surface tension of the defoamer becomes smaller. This indicates the thermodynamic tendency of defoaming.
The above statements are adequate for liquid defoamers that are insoluble in the bulk. However, experience has proven that certain dispersed hydrophobic solids can greatly enhance the effectiveness of defoaming. A strong correlation between the effectiveness of a defoamer and the contact angle for silicone-treated silica in hydrocarbons has been established. It is believed that the dewetting process of the hydrophobic silica causes the collapse of a foam by the direct mechanical shock occurring by this process.