1. Scope of application
This standard specifies a hydrostatic test method for determining the resistance of fabrics to water penetration.
This standard is mainly applicable to compact fabrics, such as canvas, oilcloth, tarpaulin, tent cloth, rainproof clothing cloth, etc.
2. Reference standards
The provisions contained in the following standards constitute provisions of this standard through reference in this standard. At the time of publication of this standard, the versions indicated were valid. All standards are subject to revision and parties using this standard should explore the possibility of using new versions of the standards listed below.
GB6529-86 Standard atmosphere for humidity control and testing of textiles (neqISO139: 1987)
3. Testing principle
The hydrostatic pressure experienced by the fabric represents the resistance encountered by water penetrating the fabric. Under standard atmospheric conditions, one side of the specimen is subjected to a continuously rising water pressure until water seeps into three places, and the pressure at this time is recorded. Water pressure can be applied from the top or bottom of the specimen. Which method is chosen should be indicated on the report.
The test results are directly related to the performance of the fabric after being subjected to water pressure for a short or slightly longer period of time.
4. Test instruments
4.1 The test instrument should be able to clamp the specimen in the following manner:
a) The sample is placed horizontally and does not bulge;
b) The area above or below the fabric that is subject to continuously rising water pressure is 100cm2;
c) During the test, the clamping device should not leak;
d) The specimen will not slip in the clamping device;
e) Minimize the possibility of water seepage at the edge of the clamping device.
4.2 The water in contact with the sample must be fresh distilled water or deionized water, and the temperature should be maintained at 20°C ± 2°C or 27°C ± 2°C. Which temperature is selected should be indicated on the test report (use higher temperature water, A lower water pressure value will be obtained, and the magnitude of its influence varies from sample to sample).
4.3 The rate of water pressure rise should be
1.00kPa/min±0.05kPa/min(10cmH2O/min±0.5cmH2O/min)
Or 6.0kPa/min±0.3kPa/(60cmH2O/min±3cmH2O/min),
The results obtained from these two different rates may be different, so which rate is selected should be indicated on the test report.
4.4 The pressure gauge is connected to the test head, and the pressure reading should be accurate to 0.05kPa (0.5cmH20).
5. Humidity control treatment and temperature and humidity testing
5.1 Humidity adjustment and temperature and humidity testing should be carried out in accordance with the regulations of GB6579 in domestic and foreign trade, commodity inspection, brand-name product evaluation and arbitration, and new product assessment.
5.2 Routine inspections or otherwise agreed upon may be conducted at room temperature or under actual conditions.
6. Sample preparation
After taking the sample, try to touch it with your hands as little as possible and avoid folding it hard. No processing (such as ironing) is performed except for humidity control. Take at least five samples from different parts of the fabric to make the samples as representative as possible. It is not necessary to cut the sample during the test, but the test should not be conducted on areas with deep wrinkles or creases.
7. Test steps
Each sample needs to be wiped with fresh distilled water or deionized water to clean the water on the surface of the clamping device, and the humidity-conditioned sample is clamped in the test head so that the fabric test surface is in contact with water. When clamping, water will not penetrate the specimen due to pressure before the test begins. Then immediately apply increasing water pressure to the sample and continuously observe signs of water seepage.
Record the water pressure when the third water droplet first appears on the sample, expressed in kPa (cmH2O). The accuracy of reading water pressure is as follows:
–Below 10kPa (1mH2O): 0.05kPa (0.5cmH2O);
–10～20kPa (1～2mH2O): 0.1kPa (1cmH2O);
–20kPa (2mH2O) and above: 0.2kPa (2cmH2O).
Ignoring those tiny water droplets that will not grow in size after they are formed, continuous water droplets seeping out from the same place on the fabric are not accumulated.
Pay attention to whether the third point of water seepage occurs at the edge of the clamping device. If the water pressure value at this time is lower than the low value of other samples of the same sample, then this data should be eliminated, and additional samples need to be tested separately until the obtained as many times as necessary for normal results.
8. Calculation and presentation of results
Calculate the average value of the test data obtained according to the method described in Chapter 7, and express each test result and its average value in kPa (cmH2O).
9. Test report
The test report should include the following:
a) Explain that the test was conducted in accordance with this standard. If there are any changes, details should be stated;
b) Atmospheric conditions used (temperate standard atmosphere, or tropical standard atmosphere, or other atmospheres);
c) Water temperature (20℃ or 27℃, or other temperatures);
d) Whether to apply water pressure from above or below the sample;
e) The water pressure rise rate is 1.0kPa/min (10cmH2O/min)
Or 6kPa/min (60cmH2O/min);
f) Which side of the fabric to test;
g) The results of each test and their average value;
h) Test date.
Tips to guide this experiment
A1 clamped specimen
In order to obtain the correct clamping state, some testers need to place a suitable rubber pad on the clamping surface.
A2 pressure gauge
A2.1 Choose a pressure gauge with an appropriate range. For fabrics with a structure similar to gabardine, use a pressure gauge with a range of 10kPa (1mH2O). For fabrics with a tighter structure, a pressure gauge with a range of 20kPa (2mH2O) should be used.
A2.2 If the pressure gauge is connected to more than one test head, in order to prevent large amounts of water from leaking through a sample that has three leaks, there should be a device that can isolate each test head separately. Because for most of these instruments, this leakage will significantly reduce the rate of water pressure rise for other specimens still under test.
A3 Measures to purify the water surface If the instrument used is such that the test water is stored in the test head and the water level rises and comes into contact with the sample, the water surface in the test head can be purified by one of the following methods. Preferred in the following order:
A3.1 Drain the test head and refill it with fresh distilled or deionized water.
A3.2 Let distilled or deionized water overflow from the test head to clean the water surface, and use a newly paraffin-coated glass piece to scrape the water surface.
A3.3 Let distilled or deionized water overflow from the test head to clean the water surface.
A4 Impact of volatile organic liquid vapor: The presence of volatile organic liquid vapor in the laboratory will affect the test results.
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