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What is surfactant?
A surfactant is a substance that, when present at low concentrations in a system, has the property of migrating and being absorbed onto the interfaces of the system and of altering to a marked degree the interfacial free energies of those interfaces
Generic Surfactant Structure
Surfactant has two ends
- One end is water soluble called Hydrophile
- Another end is water insoluble called Hydrophobe
When we put some Surfactant into water
- A few molecules will seem to dissolve
- Each hydrophobe will try to orient itself to avoid the water
- Molecules will adsorb on the walls and at the air-water interface
- Until additional surfactant cannot adsorb at the saturated interfaces, micelles will be formed.
- Micelles is an alternate mechanism for hydrophobes to avoid water.
- Micelle formation enables homogeneous emulsion and dispersion of otherwise non-compatible materials.
Types of Surfactant
1. Nonionic
• No electrical charge (o)
• Compatible with both Anionics and Cationics
• Temperature sensitive (Cloud Point)
• Steric stabilisation, poor wetting, low efficiency
2. Anionic
3. Negatively charged (-)
Most used surfactant, low cost, high efficiency
• Electrostatic stabilization, good wetting
4. Cationic
• Positively charged (+)
• Anticorrosive and Antistatic properties
5. Amphoteric
• Charge varies with pH (+/-)
HLB
Function of Surfactant
Application of Surfactant
