surface tension of liquids - surfchem.co.kr · bubble pressure method a measurement technique for...
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Du Noüy Ring Method
The traditional method used to measure surface or interfacial tension.Wetting properties of the surface or interface have little influence onthis measuring technique. Maximum pull exerted on the ring by thesurface is measured.
Wilhelmy Plate Method
A universal method especially suited to check surface tension overlong time intervals. A vertical plate of known perimeter is attached to abalance, and the force due to wetting is measured.
Spinning Drop Method
This technique is ideal for measuring low interfacial tensions. Thediameter of a drop within a heavy phase is measured, while both arerotated.
Pendant Drop Method
Surface and interfacial tension can be measured by this technique,even at elevated temperatures and pressures. Geometry of a drop isanalysed optically.
LiquidsStatic Methods
Bubble Pressure Method
A measurement technique for determining surface tension at shortsurface ages. Maximum pressure of each bubble is measured.
Drop Volume Method
A method for determining interfacial tension as a function of interfaceage. Liquid of one density is pumped into a second liquid of a differentdensity and time between drops produced is measured.
LiquidsDynamic Methods
Sessile Drop Method
This optical contact angle method is used to estimate wettingproperties of a localised region on a solid surface. Angle between thebaseline of the drop and the tangent at the drop boundary is measured.
Dynamic Wilhelmy Method
A method for calculating average advancing and receding contactangles on solids of uniform geometry. Wetting force on the solid ismeasured as the solid is immersed in or withdrawn from a liquid ofknown surface tension.
Single Fibre Wilhelmy Method
Dynamic Wilhelmy method applied to single fibres to measureadvancing and receding contact angles.
Powder Contact Angle Method
Enables measurement of average contact angle and sorption speed forpowders and other porous materials. Change of weight as a functionof time is measured.
Solids
σD = Disperse Parts of Surface TensionVan der Waals-Interaction
σP = Polar Parts of Surface TensionDipole-Dipole-InteractionHydrogen bondingLewis Acid-Base-Interaction
Surface Tension of Liquidsσ = σP + σD
Liquid Name
N,N-dimethyl-Formamidn-Decanen-Heptanen-Hexanen-Octanen-Tetradecanenitro-Ethane (Schultz)nitro-Methane (Schultz)Phthalic-acid-diethylester 22°sym-tetrabromo-Ethane (Ström)sym-tetrachloro-Ethane (Ström)tetrachloro-Methane (Schultz)Toluene (Schultz)Tricresyl-phosphate (Fowkes)WaterWater (Busscher)Water (Rabel) 22°Water (Ström) 20°α-bromo-Naphthalene (Busscher)α-brom-Naphthalene (Ström)20°
Surface Tension
37.123.920.418.421.825.631.936.837.049.736.327.028.440.972.872.172.372.844.444.6
DispersePart
29.023.920.418.421.825.627.529.830.049.736.326.726.139.226.019.918.721.844.444.6
PolarPart
8.10.00.00.00.00.04.47.07.00.00.00.32.31.7
46.852.253.651.00.00.0
Fmax
Forc
e(m
N )
Distance, d, of ring above surface (mm)
F1
F3
LamellaBreaks
0 50
5
10
Water at20 °C
1 2 3 4 6
Force During Ring Measurement
Ring
cosθLFF Vmax
ι
⋅−
=σ
Tension Surface Liquid l =σLength Wetted L =
1 cos =θ WeightLiquid toDue Force FV =
Force Total Fmax =
Liquid
Air
LiquidPlate
θ =0o
Plate madeof roughened Pt
L = WettedLength, mm
Wilhelmy Plate Method
σ =F
L cos θ
F = Force, mN
Wilhelmy Plate Method
cosθLFW
⋅=σ
Force Wetting FW =
Plate Platinum theofLength Wetted L =
1 θ cos =
Gold Plating Solution Containing FluorosurfactantsPlate Method Surface Tension versus Time Data
Time [sec]
Surf
ace-
Tens
ion
[mN
/m]
0 100 200 300 400 500 600 700 800 900 1000 110033.00
34.00
35.00
36.00
37.00
38.00
39.00
40.00
Low SurfactantConcentration
High SurfactantConcentration
Determination of Critical Micelle Concentration
25
30
35
40
45
50
55
60
65
70
75
0.1 1 10 100 1000 10,000
Log Concentration (mg/L)
Surfa
ceTe
n sio
n(m
N/m
)Surfactant Molecule Hydrophobic Portion
Hydrophilic Portion
Surfactant in
Water at 20 °C
Critical MicelleConcentration
(CMC)
Surface
Air
Water
Surfactant at Surface Micelles FormedSurface Saturated
10001001010.125
30
35
40
45
50
Critical Micelle Concentration Determination
Concentration (mg/L)
Surfa
ce T
ensi
on (
mN
/m)
CMC = 33 mg/L
Sample: Nonylphenol Ethoxylate
Solvent: WaterTemperature: 24.2 ± 0.4 °CMethod: PlateAnalysis Time: 92 minutes
CH3 (CH)2 8 (CHCH)2 2 9.5OHO
-3.5 -3.0 -2.5 -2.030
35
40
45
50
55
60
Surface Tension of Aqueous Sodium Dodecyl Sulfate
Surfa
ce T
ensi
on (m
N/m
)
Log Concentration (mM)
Sodium Dodecyl Sulfatein water at 25 °C
99% Pure
Purified by passage throughHPLC column containing300 m2/g octadecylsilanizedsilicon gel
Critical Micelle Concentration Data
Concentration [mg/l]
Surf
ace
Tens
ion
[mN
/m]
1 5 10 50 100 500 1e3 5e3 1e420.022.525.027.530.032.535.037.540.042.545.047.550.052.555.057.560.0
C15E7C15E9
C15E12
CH3 CH2 CH CH2 CH3
O
CH2
CH2X
OH
(CH2)5 (CH2)5
1 2 3 4 5 6
SURFACETENSION
SURFACTANT CONCENTRATION
1
2 3 4
5 6
CAC
CMC
Polymer / Surfactant Interaction
105
104
103
102
101
0.0 0.2 0.4 0.6 0.8 1.0
CM
C (
mic
rom
olar
of t
otal
sur
fact
ant )
MOLAR RATIO (SDS/Total Surfactant)
Aqueous CMC Data for SDS / DTAB Solutions
Inlet for Heavy Phase
Ocular
Spinning Drop Tensiometer Diagram
Window
PhaseHeavy
Illumination
Septum
Droplet ofLight Phase
Tension lInterfaciaiσ = Constant k =
Radius Drop r =VelocityAngular =ω
DropHeavy Density H = ρPhaseLight Density L =ρ
Spinning Drop
σi = kr3 ω2 (ρH - ρL)
SUMMARY
• 4 methods to measure static SFT and IFT– Ring Method of DU NOÜY
– Plate Method of WILHELMY
– Pendant Drop Techniques
– Spinning Drop Techniques
• It is important to split the SFT of a liquid into two or more components
•The advantages of plate vs. ring method:–True static method
– High stability of plate
– Fast
– No correction necessary
•SFT and IFT-techniques are important for surfactant characterization
•CMC, Surface excess and synergistic effect are important parameters which can be determined fully automatic
Dynamic Surface Tension Maximum Bubble Pressure
Pressure Sensor
Tank( 0 Bar at beginning
of measurement)
PTFE Probe( Diam. 1.5mm )
Liquid
Pressure coming in air or nitrogen4-6 Bar
Dynamic Data for Nonylphenol Ethoxylate (9.5) in Water
Surface Age [ms]
Dyn
amic
Sur
face
Ten
sion
[m
N/m
]
10 100 1000 10,000 50,00030.00
35.00
40.00
45.00
50.00
55.00
60.00
65.00
70.0010 mg/L
30 mg/L
100 mg/L500 mg/L
1000 mg/L
8000 mg/L
Light Phase to Heavy Phase Setup
GlassSample Tube
Drop
Photodiode
Capillary
CapillaryHolder
Tubing tosyringe pump
LED
LiquidLevel
Heavy Phase to Light Phase Setup
Tubing tosyringe pump
CapillaryHolder
Capillary
Photodiode
Drop
GlassSample Tube
Heavy Phase
LED
Bleed
d πgρρVσ )( L - Hdrop
i =
DROP VOLUME
Tension lInterfaciaiσ = Volume Drop Vdrop = Constanton Accelerati g =
PhaseLight Density H =ρ
PhaseLight Density L =ρ
Diameter Drop d =
Drop Volume Method
V (ρH - ρL)g = Separation Force
σi πd = Adherence Force
σi =Vdrop (ρ - ρ)g
H L
πd
Balance of Forces at the Tip
dLightphase, ρL
Heavy phase, ρH
Dynamic Interfacial Tension Datafor Alcohol Ethoxylate Solutions
100001000100100
5
10
15
20
25
1 mL/Hr0.75 mL/Hr0.50 mL/Hr0.25 mL/Hr0.10 mL/Hr
Flow Rates
Concentration (mg/L)
Dyn
amic
I nte
rfaci
a lTe
nsio
n(m
N/m
)
“Slow Surfactant”
Dense phase: Water withalcohol ethoxylate(density = 0.998 g/cm)
3
Light phase: Canola Oil(density = 0.891 g/cm)
3
Temperature: 23 ±1 °C
CMC = 100 mg/L
Method: Drop Volume
CH CH - O - CH CH - OH3 2 2 211 10
• Characterization of surfactant dynamics is an important tool for process-near optimization
SUMMARY
• The maximum bubble pressure method is a fast and easy to use technique to characterize fast diffusion of surfactants at the liquid / gas interface
• The drop volume technique is a method to characterize diffusions of surfactants at liquid / liquid - interface
• A special capillary tip design increases reproducibility and minimises experimental error