Surfactants and Manufacture of Soaps
A surfactant is an ingredient that tends to reduce the surface tension of a liquid in which it is dissolved.
So, by adding a surfactant to a cleaner, chemists are able to break down the boundaries between water and
oils or greases.
Surfactants are one of many different compounds that make up a detergent. They are added to remove dirt
from skin, clothes and household articles particularly in kitchens and bathrooms. They are also used
extensively in industry. The term surfactant comes from the words surface active agent.
Structure
Surfactants contain both hydrophilic, water-loving components, and hydrophobic, or water hating,
components that work together to help place oils in suspension, allowing them to be pulled away from the
part and into the solution. The water molecules are attracted to the hydrophilic components of the
surfactant. The insoluble materials, the oils & greases, are attracted to the hydrophobic components of the
surfactant. So as the hydrophobic end attaches to the soils, the hydrophilic end is being pulled by the
water which causes the tension necessary to ultimately pull the soil off of the surface of the part.
Surfactants function by breaking down the interface between water and oils and/or dirt. They also hold
these oils and dirt in suspension, and so allow their removal. They are able to act in this way because they
contain both a hydrophilic (water loving) group, such as an acid anion, (-CO2- or SO3-) and a hydrophobic
(water hating) group, such as an alkyl chain. Molecules of water tend to congregate near the former and
molecules of the water-insoluble material congregate near the latter.
Classification of Surface Active Agents (Surfactants)
Anionic
Negatively Charged
Most widely used surfactant for preparing shampoos because of its excellent cleaning
properties and high air conditioning effects
Particularly effective at oily cleaning, oil/clay suspension
Application
As detergents in petroleum oil recovery operation, As in contaminant
hydrogeology remediation
Head:
Sulfate
Sulfonate
Phosphate
Carboxylate
Example:
Sulfonic Acid salts
Alcohol Sufates
Alkyl Benzene Sulfonates
Phosphoric Acid Esters
Carboxylic Acid Salts
Sodium dodecyl sulfate
Catinonic
-Positively charged
-Antibacterial
-Preservative properties as they have good bactericidal property
Application
As sanitizing and antiseptic agents, antistatic agent, cosmetic
formulation, textile softener, corrosion inhibitors, form depressants, flotation
chemicals, petroleum derivatives
Head:
Primary Amine
Secondary Amine
Tertiary Amine
Example
Tetradecyltrimethyl
Ammonium Bromide
Benzal Konium Chloride w/ minimum amount of dodecyl & hexadecyl
compounds
Cetyl pyridium chloride
Cetyl Trimetyl Ammonium Bromide
Non-Ionic
-Hydrophilic head group
-Excellent grease/oil remover and emulsifier
-Do not have electrical charge which makes them resisitant to water hardness
deactivation
Application:
Good solubilizer
Widespread use in petroleum and environmental applications
Head:
Fatty Alcohols
Cetyl Alcohols
Stery Alcohols
Cetostreayl Alcohols
Oleyl Alcohols
Example:
Alcohol ethoxylates
Alkylphenol ethoxylates
Alkanolamide and sugae sulfonates
Polyethylene Glycol
Amphoteric/ Zwiterionic
very mild, making them particularly suited for use in personal care preparations over
sensitive skin
has excellent dermatological properties
they are frequently used in shampoos and other cosmetic product and also in hand
dishwashing liquid because of their high foaming properties.
Application:
Pharmaceutical industry, Paint industry, In animal feed, Textile industry
Head:
Contain Both Cationic and Anionic
Example:
Cocamidopropyl hydroxysultaine
Lecithin
Mechanism of Action Surfactants:
(a) Roll-up mechanism:
The surfactant lowers the oil/solution and fabric/solution interfacial tensions and in this way lifts the
stain of the fabric.
(b) Emulsification:
The surfactant lowers the oilsolution interfacial tension and makes easy emulsification of the oil.
(c) Solubilization:
Through interaction with the micelles of a surfactant in a solvent (water), a substance
spontaneously dissolves to form a stable and clear solution.
