contact angles
DESCRIPTION
ARVIND TOMAR Sr-08471. CONTACT ANGLES. Contact angle . FACTORS AFFECTING CONTACT ANGLE. SURFACE TENSION SURFACE ENERGY OF SOLID SURFACES INTERACTION FORCES BETWEEN LIQUID MOLECULES SURFACE ROUGHNESS TEMERATURE OF LIQUID. SURFACE TENSION. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/1.jpg)
CONTACT ANGLES
ARVIND TOMARSr-08471
![Page 2: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/2.jpg)
Contact angle
![Page 3: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/3.jpg)
FACTORS AFFECTING CONTACT ANGLE
SURFACE TENSION SURFACE ENERGY OF SOLID SURFACES INTERACTION FORCES BETWEEN LIQUID
MOLECULES SURFACE ROUGHNESS TEMERATURE OF LIQUID
![Page 4: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/4.jpg)
SURFACE TENSION
![Page 5: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/5.jpg)
SURFACE TENSION IS A CONTRACTIVE TENDENCY OF SURFACE OF A LIQUID
THIS ALLOWS IT TO RESIST AN EXTERNAL FORCE DUE TO SURFACE TENSION A LIQUID ACQUIRE
MINIMUM SURFACE AREA DUE TO SURFACE TENSION LIQUID SURFACE BAHAVES
AS A STRECHED SKIN SURFACE TENSION IS CAUSED BECAUSE OF
MOLECULER ATTRACTION FORCES IN GENERAL DISSOLVED CONTAMINATION IN WATER
REDUCES SURFACE TENSION, HENCE ALSO THE CONTACT ANGLE
![Page 6: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/6.jpg)
DUE TO SURFACE TENSION A NEEDLE CAN FLOAT ON A LIQUID
![Page 7: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/7.jpg)
SURFACE TENSION =FORCE/LENGTH =WORK DONE /AREA TO SEPRATE TWO LIQUID SURFACES WE
HAVE TO DO WORK THIS PER UNIT AREA WORK IS CALLED
SURFACE TENSION THIS WORK INCREASES POTENTIAL
ENERGY OF LIQUID
![Page 8: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/8.jpg)
AS SURFACE TENSION REDUCES, DROPLETS TENDS TO SPREADS AND CONTACT ANGLE DECREASES
GREATER THE PORTION OF POLAR GROUPS,HIGHER THE ATTRACTIVE FORCES,HIGHER SURFACE TENSION AND HIGH WILL BE THE CONTACT ANGLE
EX. WATER HAS HIGHER CONTACT ANGLE AS COMPARED TO OILS
![Page 9: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/9.jpg)
SURFACES BENDS TO BALANCE FORCES
![Page 10: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/10.jpg)
ΔP=σ[1/Rx +1/Ry]
YOUNG-LAPLACE EQUATION
![Page 11: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/11.jpg)
HIGHER THE SURFACE TENSION HIGHER WILL BE CONTACT ANGLE
![Page 12: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/12.jpg)
SURFACE ENERGY
HIGHER THE SURFACE ENERGY LOWER WILL BE CONTACT ANGLE
HIGH SURFACE ENERGY OVERCOMES SURFACE TENSION AND LIQUID DROPLET SPREADS OVER SURFACE
HIGHER THE SURFACE ENERGY HIGHER THE ADHESION
SURFACE IS ALWAYS AT HIGHER ENERGY AS COMPARED TO BULK
![Page 13: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/13.jpg)
DEPENDENCE OF CONTACT ANGLE ON SURFACE ENERGY
AND SURFACE TENSION
![Page 14: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/14.jpg)
SURFACE ENERGY DEPENDS ON CHEMICAL COMPOSITION AT SURFACE
POLAR GROUPS CAUSES HIGH SURFACE ENERGY
CLEAN METALIC SURFACES HAVE HIGH SURFACE ENERGY
BONDING BETWEEN HYDROCARBON MOLECULES IS LESS
POLYETHYNES HAVE LESS SURFACE ENERGY AND HIGHER CONTACT ANGLE
![Page 15: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/15.jpg)
FOR UNPOLISHED SURFACE THERE ARE SO MANY POLAR GROUP(EX. O-H) SO HAD HIGHER ENERGY
SURFACE ENERGY OF SURFACE CAN BE REDUCED BY POLISHING WAX
![Page 16: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/16.jpg)
WATER PROOF FABRICS FLOURINATED FABRICS, WHICH ARTIFICIALLY
MAKE A SURFACE LOW ENERGY ONE THUS MORE CONTACT ANGLE AND SURFACE IS
NON-WETTING BY FORMING OXYGEN CONTAINING
COMPOUNDS AT SURFACE A LOW ENERGY SURFACE CAN BE CONVERTED INTO A HIGH ENERGY ONE
THIS CAN BE ACHEIVED BY EXPOSURE TO UV-RADIATION,CORONA/PLASMA DISHCHARGE, ACID TREATMENT etc.
![Page 17: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/17.jpg)
NON-WETTING FABRIC
![Page 18: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/18.jpg)
![Page 19: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/19.jpg)
INTERACTION FORCES BETWEEN LIQUID MOLECULES
CONTACT ANGLE(IN DEGREES)
DEGREE OF WETTING
SOLID-LIQUID INTERACTION
LIQUID-LIQUID INTERACTION
θ=0 PERFECT WETTING
VERY STRONG VERY WEAK
0<θ<90 HIGH WETTING STRONG STRONG
WEAK WEAK
90≤θ<180 LOW WETTING WEAK STRONG
θ=180 PERFECTLY NON-WETTING
VERY WEAK VERY STRONG
![Page 20: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/20.jpg)
SURFACE ROUGHNESS
WITH INCREASING SURFACE ROUGHNESS CONTACT ANGLE DECREASES FOR HYDRO-PHILIC SURFACE
WITH INCREASING SURFACE ROUGHNESS CONTACT ANGLE INCREASES FOR HYDRO-PHOBIC SURFACE
![Page 21: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/21.jpg)
![Page 22: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/22.jpg)
TEMPERATURE
WITH INCREASING OF TEMPERATURE SURFACE TENSION DECREASES AS INTERMOLECULER FORCE DECREASES
THUS WITH INCREASING OF TEMPERATURE CONTACT ANGLE DECREASES
![Page 23: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/23.jpg)
BALANCE OF FORCES
![Page 24: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/24.jpg)
YOUNG'S EQUATION
γsl +γlg*cosθc =γsg
![Page 25: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/25.jpg)
TWO DIFFRENT LIQUIDS
![Page 26: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/26.jpg)
METHODS FOR MEASURING CONTACT ANGLE
THE STATIC SESSILE DROP METHOD THE DYNAMIC SESSILE DROP METHOD DYNAMIC WILHELMY METHOD POWDER CONTACT ANGLE METHOD
![Page 27: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/27.jpg)
Young-dupre equation
γ(1+cosθc)= ∆Wsl
Here,
∆Wsl=solid-liquid adhesion energy per unit area
![Page 28: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/28.jpg)
CALCULATION FOR CONTACT ANGLE
θc=arcCOS[rAcosθA+rRcosθR/rA+rR]
Where,
![Page 29: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/29.jpg)
ΘA= advancing angleΘR= receding angleADVANCING ANGLE:- largest contact angle
possible without increasing solid-liquid interfacial area by adding volume dynamically
RECEDING ANGLE:- if in above case you start removing volume then smaalest possible angle is called receding angle
![Page 30: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/30.jpg)
![Page 31: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/31.jpg)
Calculation of Θa and Θr on a tilted plane
![Page 32: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/32.jpg)
Hysteresis angle
H=Θa-Θr Hysteresis angle for an ideal solid surface is
zero i.e. Θa=Θr With increasing roughness H increases With increasing roughness Θa increases and
Θr decreases Increased liquid penetration leads to increased
hysteresis
![Page 33: CONTACT ANGLES](https://reader033.vdocuments.net/reader033/viewer/2022061320/56815d96550346895dcbb36c/html5/thumbnails/33.jpg)
THANK YOU