This document discusses hydrophobic materials and how they are formed. Hydrophobicity refers to materials that repel water due to having a water contact angle over 90 degrees. Hydrophobicity is achieved through microscale and nanoscale surface roughness and low surface energy. Some natural hydrophobic materials include waxes, oils, and lotus leaves. The document describes different models for how water interacts with rough hydrophobic surfaces and various methods for creating artificial superhydrophobic surfaces, such as layer-by-layer assembly and sol-gel processing. Potential applications of hydrophobic coatings include anti-corrosion, anti-icing, self-cleaning surfaces, and textiles.

1. FORMATION OF
HYDROPHOBIC
MATERIALS
PRESENTED BY GGSESTC BOKARO STEEL CITY

3. • Some of the common natural
Hydrophobic materials are
waxes, oil ,lotus leaf and fats
HYDROPHOBIC comes also from the Greek word
Hydro(water) and Phobic (fear) it refers to non polar substance
that repels a mass of water.
WHAT IS MEANT HYDROPHOBIC ?
The evaluation of hydrophobicity
is made through water contact
angle measurements.
A water droplet would be
spherical so the water contact
angle will be significantly high.

4. • A drop with a contact angle over 90° is hydrophobic.
• This condition is exemplified by poor wetting, poor
adhesiveness and the solid surface free energy is low.

5. (Hysteresis) loop
advancing contact angle
receding contact angle
1
2
contact
angle
volume
stick
slip
jump

6. Young's equation help to understand and describe the
interactions between the forces of cohesion and
adhesion and measure what is referred to as surface
energy.
www.ramehart.com/contactangle.htm

7. Understanding
nature: Physical
basis of the Lotus-
effect
The Lotus-effect (1):
Superhydrophobicity
 Microstructural
epidermal cells
Nanostructural wax-
crystals
20 μm

8. When depositing a water drop on a such solid .It can adopt at
least two type of configuration-
Quéré D , Reyssat M Phil.
Trans. R. Soc.
A 2008;366:1539-1556
conforming to the solid surface (Wenzel situation)
Sitting on the top of the posts((Cassie or fakir state)

9. Homogeneous
substrate, eq=110o
Suspended, ~160o Collapsed, ~140o
Suspended and collapsed drops

10. Rough surfaces
Wenzel: Liquid
completely fills the
grooves of the solid
Cassie and Baxter:
Liquid “sits” on the
surface roughness

11. www.me.umn.edu/~lixxx099/EFRI_CAES/Research/t

12. Hysteresis: 3 dimensions
macroscopic contact angle versus volume
A B
stick
jump

13. The Lotus-effect (2)
Self-cleaning(2)Water rolls off the surface
taking the contamination
along

14. VARIOUS METHOD ARE USED FOR THE PREPARATION
OF ROUGH SURFACES
• LAYER- BY- LAYER AND SELF
ASSEMBLY
• SOL-GEL PROCESSING
• ELECTRO-SPINING METHOD
• ELECTROCHEMICAL DEPOSITION
• CHEMICAL VAPOUR DEPOSITION

15. SUPERHYDROPHOBIC COATING CAN BE MADE FROM
MANY DIFFERENT MATERIALS
• MAGANESE OXIDE POLYSTYRENE (MNO2/PS)
• ZINC OXIDE POLYSTYRENE(ZNO/PS) NANO COMPOSITE
• SILICA NANO COATING

16. APPLICATIONS
1.A primary purpose of hydrophobic coatings such as
polytetrafluoroethylene(PTFE) or polyxylylene is to act as a
barrier against water commonly seen in automobiles
2.Used in iron and steel industry for anticorrosion .
3.Its is widely used in aerospace industry for providing anti-
icing coating on the surface of the aeroplane .
4.Hydrophobic self cleaning glasses are installed in traffic
sensor control unit.
5.Used in textile industry
.

17. CONCLUSION
• SURFACE ROUGHNESS
INCREASES HYDROPHOBICITY
• SEVERAL METHOD TO
SYNTHESIZE ARTIFICIAL
SUPERHYDRROPHOBIC
SURFACES
• IT IS RUSTLESS,DUSTLESS