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.