The 4 Main Components
Of Waterproof/Breathable Fabrics:
- The Water Repellency Rating System
- Water Resistance & Testing
Water Repellency, The First Line Of Defense:
Repellency is the the ability of the fabric to bead water on the fabric surface.
80% repellency, after 20 home launderings, is the benchmark for water repellency.
To be effective, the outer fabric needs to repel water while also enabling moisture vapor to pass through and escape.
Repellency should enhance comfort and wearer satisfaction.
Although todays DWR (durable water repellency) lasts for a very long time, proper care of the garment is essential for enhancing the performance of the DWR and to provide complete satisfaction.
First, the garment must be kept reasonably clean and it is important that proper
washing instructions are followed. After washing, the garment must be thoroughly and completely rinsed of all detergents. Also, tumble dry and finish with a hot iron (110 C max.) Dry heat only, do not steam! If these instructions are followed, water repellency of up to 80% should be obtained, even after more than 20 home launderings.
The ability of the fabric to bead water on the surface allows the moisture drops to easily roll off. This keeps the surface of the fabric clean and enables the fabric to breathe (moisture vapor will escape through the shell fabric surface).
New water repellency applications, such as our DWR SuperShed, utilize new technology that has just recently been made available. These applications allow for as much as 80% repellency for over 100 home launderings!
It is important to remember that water repellency is restored after proper washing and drying. Therefore, one cannot expect long lasting water repellency on a garment that remains unwashed for an extended time.
View the Water Repellency Rating System
View the Water Repellency Tester
Water resistance can be measured by two different methods. One is the low hydraulic pressure test, JIS L 1092 A/ISO 811. This test is used to measure water resistance up to 2,000mm, approx. 3 psi. The pressure gradient for this test is 600mm pressure rise/minute. This test is commonly called the water column test and can simulate the pressure applied by a column of water up to 6 feet high.
The second method is called the high hydraulic pressure test, JIS l 1092 B. This test is used to measure from 2,000mm to as high as 30,000mm. The pressure gradient for the test is 10,000mm pressure rise/minute.
Each method uses different equipment to measure water resistance. Both methods apply pressure, by water, to the fabric until the fabric begins to leak.
The primary difference between the two methods is the rate at which water pressure is applied to the fabric. Many technicians feel that exposure to the artificial situation created by machines is not realistic after the fabric has been on the machine over 3 minutes. Therefore, some testing may require a wire mesh screen to achieve a more realistic testing situation.
Water resistance is the ability of a fabric to withstand the penetration of water from traveling through the fabric. It is very important that methods used for the testing of water resistance are appropriate and well executed. The ASF Group produces fabrics with appropriate water resistance levels according to the end use and the price range of the garment.
Breathability, Moisture Vapor Transmission & Testing:
Breathability is the measurement of the amount of vapor or perspiration moisture transported through the barrier layer, into the atmosphere (this is true for both coatings and laminates).
There are several different test methods that can be used to measure breathability. However, there is not a global consensus that any one method can measure the conditions encountered during different end uses. It is also clear that a universal correlation cannot be obtained using different methods to test the same fabric. A specific test is needed for a specific end use condition.
The three tests that are generally used are:
1. The Upright Cup Test JIS L 1099 A1: Used to test microporous hydrophobic coatings and laminates, this test measures water or perspiration vapor transmission. Since most micro porous coatings are hydrophobic (as in water-hating) this test is not designed to measure water or perspiration absorption.
2) The Inverted Cup Test JIS L 1099 B1: This test is used to test monolithic hydrophilic films or PTFE film. Since hydrophilic non-porous films breathe by absorbing water or perspiration, this test is designed to measure the amount of water or perspiration that is absorbed.
3) The Sweating Hot Plate Test ISO 11092: Often referred to as the skin model and intended simulate the heat and mass transfer which occur next to the human skin, this test is a combined measurement of both thermal resistance and water vapor resistance. It measures the skin comfort, but does not actually measure moisture permeability, but rather heat loss through moisture evaporation.
Seam sealing is the only way to produce truly waterproof garments. In addition, the fabric, the type of tape, and the method of application are all very important. Sealing factories must be qualified and must utilize modern sealing equipment. The ASF Group provides superior tape products to our customers, and we insure that our ASF fabrics will be fully seam-sealable if the proper seam sealing techniques are utilized.
For effective seam sealing on 3-layer fabrics, it is important to realize that the surface that is being welded is not film, but instead a porous fabric. For good adhesion, the glue must completely penetrate and saturate the fabric through to the middle layer, otherwise the swelling and drying will eventually loosen the glue.
Also for 3-layer fabrics, the following are three important factors to consider in order to achieve satisfactory welding:
- the construction of the backing Tricot.
- the heat energy used to melt the adhesive completely.
- the method in which the welding is executed.