How can textiles be made waterproof? What are the standards?

 

Waterproofing fabrics is a type of functional textiles. Functional textiles are textiles that, in addition to the basic use value of their own products, also have other functions, such as waterproof, oil-proof, mildew-proof and anti-bacterial.

 

How can textile fabrics be waterproof?

 

Textiles can be given waterproof properties through waterproof finishing. Fabric waterproof finishing is divided into water-repellent finishing and hydrostatic pressure-resistant finishing.

 

Water repellent finish

 

After the fabric is treated with water-repellent finishing, the surface tension changes, and the fabric changes from hydrophilic to hydrophobic. Water dripping on it is like dripping on a lotus leaf, which can roll but cannot be wetted.

 

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 called coating finishing.

 

According to the moisture permeability of the fabric after waterproof finishing, it can be divided into moisture-permeable waterproof finishing and moisture-impermeable waterproof finishing.

 

Breathable and waterproof finishing

 

Hydrophobic substances form a continuous film on the surface of the fabric, which can prevent water from penetrating and can withstand long-term rain and a certain amount of water pressure. Clothing is usually finished with moisture-permeable and waterproof finishing, so that it has certain waterproof properties without reducing the moisture permeability of the fabric, making it comfortable to wear and not stuffy.

 

Impermeable and waterproof finishing

 

Impermeable waterproof processed fabrics are usually used for waterproof canvas, tents and packaging.

 

Principle: According to the different uses of the product, the current main evaluation indicators include water stain level, water penetration amount and hydrostatic pressure resistance level.

 

1. Water test (spray method)

 

Principle: Install the sample on the ring holder, keep the holder at 45° to the horizontal, and the center of the sample is a certain distance from the bottom of the nozzle. Spray the sample with a certain amount of distilled or deionized water. After spraying, by comparing the appearance of the sample with the description and pictures of the water staining phenomenon, the water staining level of the fabric is determined, and the waterproof performance of the fabric is evaluated.

 

Commonly used standards:

 

GB/T4745 "Testing and Evaluation of Waterproof Performance of Textiles by Wetting Method"

 

ISO4920 "Test method for surface moisture resistance of textile fabrics wet test"

 

AATCC22 "Water repellency spray test"

 

Evaluation method:

 

Take GB/T4745-2012 "Method for Detection and Evaluation of Waterproof Properties of Textiles by Water" as an example: the water level is ≥3 levels, and it has anti-wetting properties.

 

2. Rain test

 

Principle: Place a piece of absorbent paper with a known weight on the back of the test sample. After continuously spraying water for a specific period of time, the weight change of the absorbent paper is measured to measure the water permeability. The test methods are divided into horizontal spray rain test and top-to-bottom impact penetration test.

 

Commonly used standards:

 

-Horizontal spray rain test

 

AATCC35 "Water repellency rain test"

 

ISO22958 "Textiles Waterproofness Horizontal Spray Rain Test"

 

GB/T23321 "Textiles Waterproofness Horizontal Spray Rain Test"

 

-Impact penetration test

 

ISO18695 "Impact Penetration Test for Determination of Water Permeability Resistance of Textiles"

 

GB/T33732 "Determination of Water Penetration Resistance of Textiles - Impact Penetration Test"

 

AATCC42 "Waterproof Impact Penetration Test"

 

3. Hydrostatic pressure test

 

Principle: One side of the sample is subjected to rising water pressure until three water seepages appear on the other side, and the water pressure data is recorded.

 

Commonly used standards:

 

GB/T4744 "Testing and Evaluation of Waterproof Performance of Textiles: Hydrostatic Pressure Method"

 

ISO811 "Determination of water resistance of textile fabrics: Hydrostatic pressure method"

 

AATCC127 "Waterproof Hydrostatic Pressure Test"

 

Evaluation method:

 

Take GB/T4744 "Hydrostatic Pressure Method for Detection and Evaluation of Waterproof Properties of Textiles" as an example:

 

If the anti-hydrostatic pressure of textiles is ≥ level 1, it has anti-hydrostatic pressure properties. The higher the grade, the better the resistance to hydrostatic pressure.

 

The national standard textile products that have requirements for waterproof performance are mainly concentrated in outdoor products.

 

For example:

 

GB/T21980-2017 "General Technical Specifications for Professional Sports Clothing and Protective Equipment"

 

GB/T32614-2016 "Outdoor Sportswear Jackets"

 

GB/T21294-2014 "Inspection Methods for Physical and Chemical Properties of Clothing"

 

GB/T21295-2014 "Inspection methods and technical requirements for physical and chemical properties of clothing"

 

Kind tips

 

1. Choose the appropriate method to test the waterproof performance according to the use of the product and the expected effect you hope to achieve.

 

2. In recent years, the application of fluorinated compounds in water-repellent, oil-repellent, and anti-fouling finishing of fabrics has developed rapidly. Perfluorinated compounds represented by PFOA & PFOS are reproductively toxic and difficult to degrade, and have been included in the EU POPs regulations. , waterproof products exported to the EU should ensure material safety.