Waterproof and water repellent are two different concepts. Waterproof means that the fabric is completely impermeable to water, whether it is liquid water or gaseous water, while water repellent means that liquid water cannot pass through, but gaseous water is allowed to pass through.

Waterproof, water resistant/water proof (here it should refer to waterproof and breathable fabrics), generally refers to making a rubber base on the bottom of the fabric, which is divided into coating and lamination. Coating is often called coating, and lamination is a composite layer of waterproof material on the back.

Waterproof finishing only applies a dense film or material that cannot pass water on the surface of the fabric. Therefore, waterproof finishing has no requirements for the surface energy of the fabric. For example, fabrics coated with silicone, polyvinyl chloride resin, polyurethane resin, etc. are a kind of waterproof finishing. Its coating cannot pass water vapor, it prevents the evaporation of human sweat, and condenses water vapor on the inner surface of the fabric, which is very uncomfortable to wear.

Water repellent, also known as "water repellent" or "water repellent", abbreviated as W/R, is a hydrophobic compound deposited on the fiber surface, leaving pores on the fabric surface, air and water vapor can still pass through (through post-finishing), and generally form water droplets on the fabric surface (like lotus leaves). But it is not really waterproof, and water will still penetrate into it after a long time. W/R treated fabrics will become ineffective due to washing and long-term use.

Water repellent finishing allows water vapor to pass through, which means that there are still pores on the fabric surface, but liquid water is not allowed to pass through, which requires the surface of the fabric to have a very low surface energy. For example, fabric coated with polytetrafluoroethylene is a water repellent finishing.

In terms of specific performance, it can be distinguished from two aspects:

(1) Waterproof products are more durable than water repellent products, and their physical and chemical properties are more stable

(2) Waterproof products usually do not become ineffective due to washing and long-term use.

(3) Waterproof products have a higher water pressure resistance index than water repellent products, usually at least 3000MM.

(4) When applied to clothing, the main function of water repellent treatment is to reduce the absorption of water by the fabric, so that the water can be "pushed away" on the surface of the fabric; waterproof treatment is a completely impermeable barrier that keeps water out regardless of whether the fabric absorbs water.

(5) Waterproof products are tested for water pressure resistance, while splash-proof products are tested for rain. The latter is generally not coated, but uses super-splash-proof additives, whose additives are mainly organic fluorine compounds.