The thermal protection performance of protective clothing is a key test item for many protective clothing. Since people wear such clothing to work in dangerous environments, such as fire scenes or rescue moments and other high-temperature working environments, protective clothing must ensure the safety of the human body, so a reasonable evaluation of the thermal protection performance of protective clothing must be made. Here, Standard Group (Hong Kong) Co., Ltd. uses experimental methods to describe the necessity of such experiments.
Subject content and scope of application
This standard specifies the performance requirements and test methods for ordinary protective clothing for firefighters.
This standard applies to ordinary protective clothing used by firefighters and does not apply to other protective clothing such as thermal insulation clothing and fire-avoiding clothing.
Reference standards
GB 250 Grey scale for evaluating discoloration
GB 3918 Fabric tear strength test method by trapezoidal method
GB 3923 Determination of breaking strength and breaking elongation of woven fabrics by strip method
GB 4744 Textile fabrics Determination of water permeability resistance by hydrostatic pressure test method
GB 4745 Textile fabrics Determination of surface moisture resistance (water-soaking test method)
GB 5455 Textile fabrics Determination of flame retardant properties by vertical method
Water permeability test method
①, Classification by test method
(1) Field test. Field tests are expensive and time-consuming, usually taking about half a year. During the experiment, the waterproofness of the fabric after waterproof and breathable finishing is tested regularly to determine its durability. Although this method has a long cycle and high cost, the test data is accurate.
(2) Simulation test. Simulation tests must be carried out in an environmental control room. The room is equipped with an artificial rain tower, which can release water from a height of 10m to the human model at a flow rate of 450L/m2·h like a rainstorm. Water drops with a diameter of about 5 inches are sprayed from 2,000 holes on the top at a speed of about 40 km/h, reaching 90% of the maximum raindrop speed in the air. Through adjustment, showers of varying degrees can be simulated on an area of about 2m2. The surface of the human model is filled with sensors to determine the time and location of the final water penetration and other indicators. This test method greatly shortens the time required for field testing and can be completed within a few days, but the cost is higher.
(3) Laboratory testing. Compared with field testing and simulation testing, laboratory testing is less expensive, takes less time, can obtain relative results, and is more practical. Tests on the waterproofness of fabrics after waterproof and breathable finishing can be divided into three categories. The first type is the hydrostatic pressure test, such as the domestic YC312 water pressure gauge, the American standard test method ASTM D-751, and the Mullen hydrostatic tester used in the American federal standard test method FED-STD-191A 5512. The second type is the spray test, which is to continuously drip or spray water on the fabric to be tested from a certain height and angle. The time required for water to penetrate from the sprayed side of the fabric to the other side can be measured, and the amount of water absorbed by the sample after a certain period can also be measured or the water stain morphology of the sample can be observed. The domestic ISO 4920 rainproof performance test adopts this principle.
②, Classification by the form of pressure
(1) Dynamic method. Continuously increase the water pressure on one side of the fabric and measure the hydrostatic pressure that the fabric can withstand until a specified number of water drops appear on the other side of the fabric.
(2) Static method. Maintain a certain water pressure on one side of the fabric and measure the time required for water to penetrate from one side to the other side.
Classification by the value of hydrostatic pressure that can be withstood
(1) Low-pressure test method. Standard test methods include China National Standard GB/74744-1997 "Hydrostatic Test for Determination of Water Penetration Resistance of Textile Fabrics"; China Industry Standard FZ/T01004-1991 "Hydrostatic Test for Determination of Water Penetration Resistance of Coated Fabrics" in the low-pressure method; Canadian Standard (CGSB)-4.2No.26.3-1995 "Hydrostatic Test for Determination of Water Penetration Resistance of Textile Fabrics"; International Standard ISO1420-1987 "Hydrostatic Test for Determination of Water Penetration Resistance of Rubber and Plastic Coated Fabrics"; Japanese Industrial Standard JIS L-1092 "Hydrostatic Test A for Water Resistance of Textiles"; American Association of Textile Chemists and Colorists Standard AATCC 127 "Hydrostatic Test for Water Resistance of Textiles"; American Standard Test Method (or American Society for Testing and Materials Standard) ASTM D751-1995 "Determination of Water Resistance of Coated Fabrics B" and other methods.
(2) High-pressure test method. Standard test methods include the high-pressure method in FZ/T01004-1991 "Hydrostatic test for determination of water permeability of coated fabrics"; ISO 1420-1987 "Hydrostatic test for determination of water permeability of rubber and plastic coated fabrics"; JIS L-1092 "Hydrostatic test B for water resistance of textiles"; ASTM D751-95 "Procedure A for determination of water resistance of coated fabrics"; US Federal Standard Test Method FED-STD-191A 5512 and ASTM D3393 "Standard Description of Waterproofness of Coated Fabrics" and other methods.
Factors affecting fabric water pressure resistance
The waterproof index of waterproof and breathable fabrics depends on the following factors.
(1) The tightness of the fabric. The increase in the distance between the yarns will directly affect the water pressure resistance. Generally, the tighter the fabric structure, the better its water permeability resistance.
(2) The size of the coating membrane pore size. The larger the membrane pore size, the worse the hydrostatic pressure resistance of the coated fabric.
(3) The size of the contact angle is 0. When 0>90°, the fabric has water repellency. At this time, as 0 increases, the water pressure resistance value of the fabric also increases accordingly.
(4) Coating thickness. If the coating is too thin, the coating agent cannot easily form a continuous film on the surface, and the water pressure resistance of the coated fabric is reduced; if the coating is thick, the water pressure resistance of the fabric is improved.
(5) Fabric thickness. The thicker the fabric, the greater the moisture resistance and the greater the water pressure resistance value.
(6) Yarn thickness. For a dense fabric woven from fibers with good hygroscopicity, due to the existence of the capillary effect, reducing the yarn radius can improve the fabric's water permeability.
(7) The quality of warp and weft yarns. Under the action of water pressure, the warp and weft yarns with good elasticity are easy to stretch, resulting in the formation of gaps between adjacent warp and weft yarns, and water droplets are easier to penetrate through them, which reduces the water pressure resistance value of the fabric.
(8) Coating quality. The entire fabric surface is required to be uniform and have a certain fastness. The better the coating quality, the better the water permeability resistance.
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