Wettability refers to the existence of two mutually insolubleliquid, liquid firstwettingThe ability of a solid surface, that is, a liquid in asolidThe ability of surface spreading orTendentiousness[1], for tablets, granules and other solid preparationsDisintegration、SolubilityAnd so on.
Chinese name
Wettability
Foreign name
Wettability
Definition
Ability of liquid to spread on solid surface
Metrics
Contact angle size
Nature
Determined by the properties of atoms or atomic clusters in the interface layer
The molecular state on the surface of a substance is different from that in its interior,Surface layerThe energy of a molecule is higher than that of its internal molecules.When a solid substance contacts with a liquid substance, once an interface is formed, it will decreaseSurface energyOfadsorbentPhenomenon: liquid substances will spread on the surface of solid substances.The spreading of liquid on solid surface is called wetting, and the spreading ability of liquid on solid surface is called wettability of liquid on solid[2]。
Measurement of Wettability
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As 1
In practicecontact angleTo measure the wettability of the solid surface (hydrophilic orHydrophobicDegree).When bubbles attach to the solid surface (or water droplets attach to the solid surface), it is generally considered that the contact point is three-phase contact, and this contact line is called "three-phase wetting periphery".In the process of contact, the wetting perimeter can be moved, or become larger or smaller.When the change stops, it indicates thatfree energy(expressed as interfacial tension) has reached equilibrium. Under this condition, the included angle between the tangent line of the liquid gas interface and the tangent line of the solid liquid interface at any point on the wetting periphery is called equilibrium contact angle, referred to as contact angle, as shown in Figure 1 and expressed in θ[3]。
When solid liquid gas three-phase interfacial tension is in equilibrium, the basic equation of wetting is as follows, also called wetting equation.
Where: cos θ - interface contact angle;
σs-g- solid gas contact surface;
σs-l- is the solid-liquid contact surface;
σl-g- Liquid gas contact surface;
The formula shows that the equilibrium contact angle θ is a function of the free energy (surface tension) of the three-phase interface, which is related not only to the properties of the solid surface, but also to the properties of the gas liquid interface.Cos θ is called the "wettability" of solid surface. By measuring the contact angle, the wettability and floatability of solid can be roughly evaluated.The minimum contact angle is 0 ° and the maximum is 180 °.The smaller the contact angle, the better the solid wettability.
θ=0，The liquid completely wets the solid surface, and the liquid spreads on the solid surface;
0<θ<90 °, liquid can wet solid, and the smaller θ, the better the wettability;
90 °<θ<180 °, liquid cannot wet solid;
θ=180 °, completely non wetting, the liquid condenses on the solid surface to form a small ball.
influence factor
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The wettability of solid surface is mainly determined by the interface layer atoms orAtomic clusterTherefore, the wettability of solid will vary greatly with the composition and properties of solid-liquid two phasesSurface modifierThe wettability of the subsequent solid will be independent of the properties of the solid substrate, mainly depending on the properties of the modifier and the liquid phase[4]。
The wettability in rock fluid is affected by interfacial tension.Changing the rock or the type of fluid in it will change the interfacial tension and therefore the wettability of the system.Add chemicals, such assurface active agent 、polymer、preservative、Scale removerAnd will also change its wettability.
