Cleansing action of soap: An application of ionic micelles formation:

Let us take an example of oil or grease stick on the cloth (Fig i). When it come in contact with soap solution, the stearate ions arrange themselves around it in such a way that hydrophobic parts of the stearate ions (R) are in the oil or grease and the hydrophilic parts project outside the oil droplet. 

(http://ask.learncbse.in/uploads/db3785/original/2X/c/c4f7b8ae6a369163f36e62787cda96f3f1a2cdf2.png)

As hydrophilic part is polar, these polar groups can interact with the water molecules present around the oil droplet. As a result, the oil droplet is pulled away from the surface of the cloth into water to form ionic micelle which then washed away with the excess of water. In fact, the stearate ions of soap molecules help in making a stable emulsion of oil with water which is washed away with excess of water.

     3. Emulsifying Agents (Oil in water)

When water and oil are mixed together and vigorously shaken, a dispersion of oil droplets in water - and vice versa - is formed. When shaking stops, the phases start to separate. 

However, when an emulsifier is added to the system, the droplets remain dispersed, and a stable emulsion is obtained.

An emulsifier consists of a water-loving hydrophilic head and an oil-loving hydrophobic tail. The hydrophilic head is directed to the aqueous phase and the hydrophobic tail to the oil phase. 

2. Detergents

Detergents are surfactants that help remove soils from solid surfaces. Over and above reducing water's surface tension, detergents must adsorb onto the soil's surface to aid in spontaneous release. Detergents must also keeps the soil suspended to prevent re-deposition. 

Ø  Detergents are surfactants used  for removal of dirt.

Ø  Detergency involves:

•      Initial wetting of the dirt and the surface to be cleaned.

•      Deflocculation and suspension, emulsification or solubilization of the dirt particles
•      Finally washing away the 

dirt.http://d25smtqkk0nuqw.cloudfront.net/wp-content/uploads/2015/11/biorf11.gif

Following can be understand from the above figure:
1. Dirty Substrate (Any textile material)  come in contact with detergent or surfactant in the presence of water
2. Detergent molecules start coming toward dirt or soil. As the dirt is oily in nature hydrophobic tail come in contact with dirt and hydrophilic head of detergent molecule remain in water.

3. Slowly detergent surrounded dirt particles and pulling them out of substate
4. All the dirt particles removed from the substrate.

Surfactants: Surfactants are surface active agents. Surfactant are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and lower the interfacial tension between two liquids.

Surface active agent: Certain substances like soaps ,sulphonic acids and organic compounds like methyl alcohol , acetone which when added to the water even in small amount decrease the surface tension of water  to a considerable extent. Such substances which lower the surface tension of water is called surface active agent.

Each surfactant molecule has a hydrophilic (water-loving) head that is attracted to water molecules and a hydrophobic (water-hating) tail that repels water and simultaneously attaches itself to oil and grease in dirt.

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A surfactant or surface active agent is a substance that, when dissolved in water, gives a product the ability to remove dirt from surfaces such as the human skin, textiles, and other solids.

Principal of Surfactant: Surfactants are also referred to as wetting agents and foamers. Surfactants lower the surface tension of the medium in which it is dissolved. By lowering this interfacial tension between two media or interfaces (e.g. air/water, water/stain, stain/fabric).

Role of Surfactant in wet processing:

All textile processes use water as a process medium. In order to conduct these processes, the textile substrate must be totally wetted out. Surfactants are necessary to lower the surface tension of process solutions for uniform application.

In fibre manufacture of synthetic/regenerated fibres and yarn spinning of cotton, wool, and their blends, surfactants are often sprayed on the fibre and yarn surface to reduce fibre-fibre and fibre-metal friction, referred to as yarn lubricants.

In textile dyeing, surfactants are broadly used as wetting agent, dispersants and leveling agents to help uniform dying and better dye penetration.

Dye fixatives and dye carriers are also surface active although they are not as common as other dyeing assistants.

In textile finishes, surfactants are often used as fabric softeners to improve fabric hand or feel and used as antistatic agents to control static electricity built up on the surface of textile fibres, particularly on synthetic fibre due to their low moisture contents.

Surfactants are also useful to control foam formation during textile processes, referred as antifoaming agents, particularly in dyeing and other processes with high-speed padding.