In recent years, people's love for outdoor nature has become stronger. Picnicking and camping have also become emerging social activities. However, the weather is changeable, and the rainstorm often comes at an unexpected time, so the waterproof "equipment" for outdoor activities cannot be lacking——

Umbrellas, waterproof clothing, rain boots, tents... In this issue, we will discuss the waterproof performance of textiles.

How can textile fabrics be waterproof?

Waterproof finishing can enhance the waterproof performance of textiles. Fabric waterproof finishing is divided into water repellent finishing and hydrostatic pressure resistant finishing.

■ Water repellent treatment

After water repellent treatment, the surface tension of the fabric changes from hydrophilic to hydrophobic, and water droplets on it can roll but not wet, just like on a lotus leaf.

■ Hydrostatic pressure resistant finishing

The surface of the fabric is coated with an impermeable continuous film to block the gaps in the fabric tissue and prevent water droplets from passing through. This method is also known as coating finishing.

According to the moisture permeability of the fabric after waterproof finishing, it can be divided into breathable waterproof finishing and non breathable waterproof finishing.

■ Moisture permeable and waterproof finishing

Hydrophobic substances form a continuous film on the surface of fabrics, which can prevent water infiltration and withstand prolonged rain and certain water pressure. Clothing is usually treated with moisture permeable and waterproof finishing, which gives it a certain degree of waterproof performance without reducing the moisture permeability of the fabric, making it comfortable to wear without stuffiness.

■ Non breathable and waterproof finishing

Non permeable waterproof processed fabrics are commonly used for waterproof canvas, tents, and packaging

How to evaluate the waterproof performance of textiles?

Principle: According to different product uses, the main evaluation indicators currently include water immersion level, water permeability, and resistance to hydrostatic pressure level.

1. Water immersion test (spray method)

Principle: Install the sample on the annular gripper, keeping the gripper at a 45 ° angle to the horizontal, and keeping the center of the sample at a certain distance below the nozzle. Spray the sample with a certain amount of distilled water or deionized water. After spraying, the water level of the fabric is determined by comparing the appearance of the sample with the description of the water phenomenon and pictures, and the waterproof performance of the fabric is evaluated based on this.

Common standards:

GB/T 4745 "Testing and Evaluation of Waterproof Performance of Textiles - Water Staining Method"

ISO 4920 "Testing method for surface moisture resistance of textile fabrics - Wetting test"

AATCC 22 "Water repellent spray test"

Evaluation method:

Taking GB/T 4745-2012 "Testing and Evaluation of Waterproof Performance of Textiles by Wetting Method" as an example: Wetting grade ≥ 3, it has anti wetting performance.

2. Rain test

Principle: Place a known weight of absorbent paper on the back of the test sample, and after a specific period of continuous watering, weigh the weight change of the absorbent paper to measure the water permeability. The testing methods are divided into horizontal spray rain test and top-down impact penetration test. Common standard: Horizontal spray rain test

AATCC 35 "Water repellent performance rain test"

ISO 22958 "Horizontal spray rain test for waterproofing of textiles"

GB/T 23321 "Textile Waterproofing - Horizontal Spray Rain Test"

-Impact penetration test

ISO 18695 "Determination of water resistance of textiles - Impact penetration test"

GB/T 33732 "Determination of water resistance of textiles - Impact penetration test"

AATCC 42 "Waterproof Impact Penetration Test"

3. Hydrostatic pressure test

Principle: One side of the sample is subjected to continuously increasing water pressure until three water seepage points appear on the other side, and the water pressure data is recorded.

Common standards:

GB/T 4744 "Testing and Evaluation of Waterproof Performance of Textiles: Hydrostatic Pressure Method"

ISO 811 "Determination of water resistance of textile fabrics: Hydrostatic method"

AATCC 127 "Waterproof Hydrostatic Pressure Test"

Evaluation method:

Textiles with a static water pressure resistance of ≥ 1 level have static water pressure resistance performance. The higher the level, the better the resistance to hydrostatic pressure. Taking GB/T 4744 "Testing and Evaluation of Waterproof Performance of Textiles - Hydrostatic Pressure Method" as an example:

The national standard textile products that require waterproof performance are mainly concentrated in outdoor products

For example, GB/T 21980-2017 "General Technical Specification for Professional Sportswear and Protective Equipment"

GB/T 32614-2016 "Outdoor Sports Clothing - Submachine Clothing"

GB/T 21294-2014 "Methods for Testing the Physical and Chemical Properties of Clothing"

GB/T 21295-2014 "Methods and Technical Requirements for Testing the Physical and Chemical Properties of Clothing"