Unlocking the Chemistry: Hydrophilic Transformation of Nonwoven Fabrics

Hydrophobic Nature of Nonwoven Fabric

Nonwoven fabric, especially polymeric ones like polypropylene or polyethylene, is typically hydrophobic, meaning it repels water. This hydrophobic nature is a challenge for applications where water absorption is required, like in absorbent articles.

Surfactant Application:

A surfactant is a compound that reduces the surface tension of a liquid, allowing it to spread more easily. When the surfactant is applied to the nonwoven fabric, it modifies the surface properties.

A surfactant, or surface-active agent, is typically composed of a hydrophilic (water-attracting) "head" and a hydrophobic (water-repelling) "tail."

When applied to the hydrophobic nonwoven fabric, the hydrophobic tails of the surfactant molecules are attracted to the surface of the fabric, while the hydrophilic heads face outward.

The Chemistry Behind It

Water molecules are cohesive; they tend to stick together due to hydrogen bonding.

The hydrophobic tails of the surfactant disrupt this cohesive force by inserting themselves between water molecules.

This action reduces the attractive forces among water molecules at the surface, leading to a decrease in surface tension.

The surfactant essentially "spreads out" on the fabric surface, lowering the energy required for water to wet the fabric.

The reduced surface tension makes the nonwoven fabric more receptive to water, causing it to become wettable.

The fabric, once hydrophobic, now allows water to spread across its surface rather than forming droplets or being repelled.

For Example Some Hydrophilic surfactant made of Octylphenoxypolyethoxy Ethanol-

Octylphenoxypolyethoxy ethanol is a non-ionic surfactant with a hydrophilic head consisting of polyethylene glycol chains and a hydrophobic tail composed of an octylphenol group.

The polyethylene glycol chains in the head make it hydrophilic, while the octylphenol group imparts hydrophobic properties.

Interaction with Water:

Hydrophilic Head: The polyethylene glycol chains in the head of the surfactant molecule have a high affinity for water. They form hydrogen bonds with water molecules, promoting dissolution and creating a water-attracting surface.

Interaction with Hydrophobic Nonwoven Fabric:

Hydrophobic Tail Attachment: The hydrophobic tail, composed of the octylphenol group, tends to interact with hydrophobic surfaces, such as those of the nonwoven fabric.

Surface Tension Reduction

As the surfactant molecules adsorb onto the fabric surface, the hydrophobic tails embed themselves into the fabric, reducing the cohesive forces among fabric fibers.

Wetting Action

The hydrophilic head, facing outward, now attracts water molecules. This reduces the surface tension of the water and facilitates its spread across the previously hydrophobic fabric.

Overall Process

The surfactant essentially acts as a mediator between water and the hydrophobic fabric. It lowers the energy required for water to wet the fabric by reducing surface tension.

The surfactant molecules form a monolayer on the fabric surface, making it more amenable to water absorption and modifying its original hydrophobic nature.

In Summary

The hydrophilic head of octylphenoxypolyethoxy ethanol attracts water, and its hydrophobic tail interacts with the hydrophobic fabric, creating a bridge between the two.

This surfactant-driven interaction leads to a significant reduction in surface tension, allowing water to wet the nonwoven fabric efficiently.

The reduced surface tension enables the fabric to become wettable. This means that instead of repelling water, the fabric allows water to spread across its surface. Additionally, in the described invention, a hydrophilic polymer is also applied, which further enhances the fabric's ability to interact with and absorb water.

Understanding this chemistry helps in appreciating how the addition of surfactants can transform the hydrophobic nature of nonwoven fabrics, making them hydrophilic and enhancing their performance in various applications.