Classification of SURFACTANT

Surfactants can be classified in the following ways 

1. According to their uses 

2. According to their ionic nature 

1. According to their uses: These may be classify as given below as per their applications: 

Wetting agents,  Solubilizing agents,  Emulsifying agents, Dispersing agents, Suspending & Deflocculating agents, Foaming and antifoaming agents, Detergents

2. According to their ionic nature : Ionic and Non Ionic
Ionic can further divided in to Anionic, Cationic and Amhoteric or Zwitterionic

Anionic: Those that develop a negative charge on the water solubilizing end.
Cationic: Those that develop a positive charge on the water solubilizing end.
Non-Ionic: Those that develop no ionic charge on the water solubilizing end. 
Amphoteric or Zwitterionic (: Those that have both a positive and negative charged group on the molecule.

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. 

Surface tension:

Molecules of the liquid at the surface are in different situation than those in the interior of the liquid. Molecule lying inside the liquid (As shown in figure as 'A') is surrounded by other molecules and so attracted equally in all directions. Hence the net force of attraction acting on the molecule is zero. But a molecule lying at the surface (As shown in figure as 'C') is attracted downwards by the molecules lying in the bulk of the liquid. Thus a molecule lying at the surface experiences a net inward attraction. As a result of this inward pull on all molecules lying at the surface, the surface behaves as if it were under tension. This property of liquid is called surface tension. Unit of surface tension is Dyne per cm. 

Classifications of Chemical Auxiliaries: i) Permanent or Temporary auxiliaries 

ii) Nature of auxiliaries (Surface active/non surface active/soluble/dispersing or emulsifying) 

i) Permanent or Temporary auxiliaries: 

Chemicals which are never remain with textile materials and need to be removed after processing come under Temporary auxiliaries. Examples of these chemicals are sizing chemicals, enzymes, detergents, wetting agents, leveling agents, carriers, dispersing agents, thickeners etc.

In case of permanent auxiliaries the chemicals which permanently fix on the textiles like softeners, water proofing agent, flame retardant chemicals, water repellent chemicals, rot proofing agents, binders, dye fixing agents etc.

ii) Nature of auxiliaries (Surface active/non surface active/soluble/dispersing or emulsifying/Inorganic chemicals) 

a) Surface active agents are those which act on the surface first and then react with the textiles. These are detergents, softeners, wetting agents, water repellent agent, emulsifier, dispersing agents, dyeing assistant etc

b) Non surface active agents are those which mostly not react with the textiles and remain only on the surface. Examples of these are resin, cross linking agents, sizing chemicals, thickener, binder etc.

c) There are some chemical auxiliaries which have non surface active with small amount of surface active agents properties. These are wax emulsions, silicone emulsion, spin finish oils etc.

d) Inorganic chemicals are reducing agents, acids like acetic acid, buffers to maintain pH, bleaching agents, mordants, oxidizing agents, hydrolyzing agents etc

What is Textile Auxiliaries?

At various stages of textile wet processing different types of chemicals and auxiliaries are used. Though all are actually chemicals, in practice the materials without which a process cannot be complete are termed as “chemicals” and the other substances which facilitate or improve the performance of that process are termed as “auxiliaries”. 

Auxiliaries are those chemicals which help processing operation such as preparation, dyeing, printing or finishing to be carried out more effectively. Some of the cases these chemicals are essential if a given effect such as wash & wear, water repellent, flame retardant, aroma finish, anti odour, colour deepening etc. is to be obtained. 

Classifications of Chemical Auxiliaries:

These can be classifies in to two ways:

i)             Permanent or Temporary auxiliaries

ii)           Nature of auxiliaries (Surface active/non surface active/soluble/dispersing or emulsifying) 

 Inauguration of Fabric smoothness Tester developed at NITRA. It is ready for commercialization.

A new instrument to measure surface smoothness characteristics of fabric.