Difference Between Wetting Agent and Surfactant

Difference Between Wetting Agent and Surfactant

The key difference between wetting agent and surfactant is that wetting agents can reduce the surface tension, allowing the liquid to spread drops to a surface, whereas surfactants can lower the surface tension between two substances.

Wetting agents are a type of surfactants.  Other forms of surfactants include detergents, emulsifiers, foaming agents.

What is a Wetting Agent?


Wetting agents are chemical substances that can reduce the surface tension of water, allowing it to spread drops on a surface.  Therefore, these substances can increase the spreading abilities of a liquid.  When the surface tension is lowered, it can lower the energy that is required to spread the drops onto a film;  therefore, it weakens the cohesive properties of the liquid and strengthens the adhesive properties of the liquid.  For example, the formation of micelles is a result of adding wetting agents to a liquid.  Usually, a micelle contains hydrophilic heads, which forms an outer layer around lipophilic tails.  In water, the tails of the micelles can surround an oil droplet, whereas the heads are attracted to the water.

Major Types of Wetting Agents
There are four major types of wetting agents known as anionic, cationic, amphoteric and nonionic wetting agents. Generally, anionic, cationic and amphoteric wetting agents tend to ionize upon mixing with water. Here, amphoteric agents can act as either cationic or anionic agents. On the other hand, nonionic wetting agents do not ionize in water. 

What is a Surfactant?

The term surfactant refers to surface-active agents. In other words, the surfactant compounds can reduce the surface tension between two substances; two substances can be two liquids, a gas and a liquid or a liquid and a solid. There are three major types of surfactants: anionic, cationic and nonionic surfactants. These three types differ from each other according to the electrical charge of the compound. 

The term anionic surfactant refers to a type of surface-active agents that contain negatively charged functional groups in the head of the molecule. Such functional groups include sulfonate, phosphate, sulfate and carboxylates. These are the most common surfactants we use. For example, soap contains alkyl carboxylates.

Cationic surfactants are a type of surface-active agents that contain positively charged functional groups in the head of the molecule. Most of these surfactants are useful as antimicrobials, antifungal agents, etc. It is because they can disrupt the cell membranes of bacteria and viruses. The most common functional group we can find in these molecules is ammonium ion.

Nonionic surfactants are a type of surface-active agents that have no net electrical charge in their formulations. That means the molecule does not undergo any ionization when we dissolve it in water. Furthermore, they have covalently bonded oxygen-containing hydrophilic groups. These hydrophilic groups bind with hydrophobic parent structures when the surfactant is added to a sample. The oxygen atoms in these compounds can cause the hydrogen bonding of the surfactant molecules.

What is the Difference Between Wetting Agent and Surfactant?

Wetting agents are a type of surfactants. The key difference between wetting agent and surfactant is that wetting agents can reduce the surface tension allowing the liquid to spread drops onto a surface, whereas surfactants can lower the surface tension between two substances. Wetting agents can be classified as anionic, cationic, amphoteric and nonionic wetting agents, whereas surfactants can be classified as anionic, cationic and nonionic surfactants.

The below infographic lists the differences between wetting agent and surfactant in tabular form.

Summary – Wetting Agent vs Surfactant

Wetting agents is a type of surfactants. Other forms of surfactants include detergents, emulsifiers, and foaming agents. The key difference between wetting agent and surfactant is that wetting agents can reduce the surface tension allowing the liquid to spread drops onto a surface, whereas surfactants can lower the surface tension between two substances.

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