How does waterproof agent make clothes waterproof

In recent years, the concept of waterproof and oil proof has been widely used, and the market share has increased year by year.

The fabric with waterproof and oil proof finish can be waterproof, rainproof, oil proof, breathable, moisture permeable and impermeable. The waterproof and oil proof tablecloth and car protective cover used in decoration and industrial production are also very popular. So what is the basic principle of waterproof agent for textile products?

What is the principle of lotus leaf effect?

In fact, the lotus leaf surface has a very complex multiple nano and micro scale ultrastructure, the surface is covered with many tiny papillae.

The hollow between them is filled with air, which forms a layer of air only nanometer thick close to the leaf surface. The raindrop forms a ball under its own surface tension, and the water ball absorbs dust during rolling and rolls out of the leaf surface to realize self-cleaning, which is called "lotus leaf effect"

But once the lotus leaves are soaked in water for a period of time, the air is eliminated, and the water molecules enter little by little, and then they become hydrophilic. Because the wetting process of liquid to solid is actually the process of liquid replacing gas on solid surface.

What is the principle of textile waterproof agent?

Textile is made of fibers and fibers by overlapping and interweaving the van der Waals force and hydrogen bond force between molecules. Due to the porous nature of fibers and the gap between fibers, there are many "capillaries" inside the fibers on the surface of textile, which are very easy to be wetted by liquid.

The mechanism of water and oil proofing is to form a layer of concave convex film on the textile surface, so that the critical surface tension of the liquid is greater than the surface of the contact surface, so as to achieve the waterproof effect. If the wetting critical surface tension of the fabric is to be less than that of the liquid, the contact angle between the liquid and the fabric is to be smaller θ Over 90 °

 However, there are still gaps on the surface of textile products. The waterproof finished fabric will still penetrate when it stays in water for a long time. If it is under pressure, water will also penetrate into the fabric.

Combined with the above, the factors affecting water and oil repellency are as follows:

1. Surface roughness of textile: if the contact angle of droplet on smooth surface is less than 90 °， Then the contact angle on the rough surface will be smaller; The contact angle on smooth surface is greater than 90 °， The contact angle on the rough surface will be larger. That is: a smooth surface that can not be wetted by water, if the surface is rough, it can not be wetted by water; A smooth surface that can be wetted by water is more likely to be wetted if its surface is rough

2. Capillary gap size of textile: when the contact angle is greater than 90 °（ In the case of oil and water repellent or oil repellent, reducing the yarn gap, that is, improving the tightness and bulk density of the fabric, can improve the water permeability of the fabric, which is conducive to the water or oil repellency of the fabric.

The waterproof finished clothes can prevent the fabric from penetrating when it meets with water, and can give the fabric anti moisture and anti penetration effect in a short time, so when it meets a small amount of water for a short time, it can temporarily prevent the fabric from wetting. In a certain period of time to wipe off the water droplets on the textile fabric, it is still possible to keep the fabric breathable and dry.

At present, the best waterproof and oil proof finishing agent is fluoropolymer. C8 and C6 are the mainstream products in the textile waterproof agent market, which are all fluorocarbon waterproof agents.

C8 waterproof agent is now all waterproof agent, the most cost-effective, the best effect. Generally, the effect of 80% dosage of C8 waterproof agent is equal to that of 100% dosage of C6 waterproof agent.