Adhesion

1
Adhesion Cohesion
2
Surface Tension Components
W12 -g12 2(g1LWg2LW) 2(g1Ag2B) 2(g1Bg2A)
3
Spreading
S Wa Wc g2 - g1 - g12
S gt 0 liquid spreads on surface S lt 0 liquid
does not spread
4
Contact Angle
Youngs Equation Force balance at 3-phase
contact point
5
Real Surfaces
Roughness
Wenzel
gLV
gSL gLVcosqsmooth gSV
q
rcosqsmooth cosqrough
gSL
gSV
qsmooth lt 90 qrough -gt 0 qsmooth gt90 qrough -gt180
lo
r l/lo gt 1
l
6
Roughness
7
Real Surfaces
heterogeneity
Cassie-Baxter
Several areas having different surface energy (gi)
gS,i L gLVcosqi gS,i V
cosqmeas S(ficosqi)
8
Spreading
hysteresis
qa
qr
qa gt qr
Hysteresis qa - qr
9
Measuring Solid Surface Tension Components
Zisman
Homologous nonpolar
gd gc
10
Measuring Solid Surface Tension Components
Van Oss-Chaudhury-Good
W12 -g12 2(g1LWg2LW) 2(g1Ag2B) 2(g1Bg2A)
W12 -g12 g1 g2 -gSL gSV gLVgLV(1cosq)
gSV-gSL gLVcosq
gLV(1cosq) 2(gLVLWgSVLW) 2(gLVAgSVB)
2(gLVBgSVA)
11
Measuring Solid Surface Tension Components
Van Oss-Chaudhury-Good