A brief analysis of the testing points for flame retardant textiles
With the progress of urban modernization, people’s awareness of fire prevention of fabrics is increasing day by day. In order to reduce fire accidents caused by fabrics and avoid unnecessary losses, the testing of fabric combustion properties has attracted attention from countries around the world in recent years. In view of the different uses of fabrics, fire protection regulations formulated by various countries have also begun with aircraft interior fabrics, carpets and building materials, and expanded to pajamas, furniture sofa covers, mattresses and interior decorations. Countries such as the United Kingdom, the United States, and Japan also stipulate by law that the work clothes and pajamas of women, children, the elderly, and disabled people must be marked “fireproof”. Our country’s work in this area is also constantly increasing its efforts.
Almost all fabric materials are flammable, and even if they are treated with fireproof technology, it is difficult to prevent the fibers from burning in flames. However, after fire-proof treatment, the burning speed of the fabric material will be reduced to varying degrees and it can quickly stop burning after leaving the fire source. Therefore, fire-proofing is relative rather than absolute.
1 Evaluation of fabric fire resistance
Evaluating the flammability of fabrics is mainly considered from two aspects: on the one hand, the ignitability, that is, the level of the ignition point, which indicates the difficulty of the fabric catching fire; on the other hand, the burning performance of the fabric, that is, the fire resistance.
There are two criteria for evaluating the burning performance of fabrics: one is based on the burning rate of the fabric. That is, the fabric after fireproofing is exposed to the flame for a certain period of time according to the prescribed method, and then the flame is removed, and the time for the fabric to continue burning with flames and the time for burning without flames is measured, as well as the degree of damage to the fabric. The shorter the flame burning time and the flameless burning time, and the lower the degree of damage, the better the fire resistance of the fabric; conversely, the fire resistance of the fabric is poor.
The other is to judge by the oxygen index (also called the extreme oxygen index) method. Fabrics require oxygen to burn. The oxygen index (LOI) is an expression of the oxygen required for fiber combustion. Therefore, the fire resistance of fabrics can be determined by measuring the oxygen index. The higher the oxygen index, the higher the oxygen concentration required to maintain combustion, which means The harder it is to burn. This index can be expressed by the small volume percentage of oxygen required for the sample to maintain candle-like combustion in a mixed gas of nitrogen and oxygen: LOE = oxygen concentration/(oxygen concentration + nitrogen concentration) × 100%. If the oxygen index is less than 20%, it is flammable Fiber; an oxygen index between 20 and 26% is a flammable fiber; an oxygen index between 26 and 34% is a flame-retardant fiber; an oxygen index above 35% is a non-flammable fiber.
2 Test methods for fire performance
There are various combustion test methods, and it is difficult to compare the test results of various test methods with each other. The experimental results can only illustrate the quality of the sample’s combustion performance to a certain extent. The combustion experiment method is mainly used to test the combustion extent (charring area and damage length), afterburning time and smoldering time of the sample. According to the relative position of the sample and the flame, it can be divided into vertical method, tilt method and horizontal method.
my country currently mainly uses GB/T5455~1997 “Vertical Method for Testing the Combustion Performance of Fabrics” for testing the fire resistance of workwear. The principle is to place a sample of a certain size vertically in a specified combustion test chamber and ignite it with a specified fire source for 12 seconds. After removing the fire source, measure the afterburning time and smoldering time of the sample. After the smoldering stops, press Determine the length of damage using prescribed methods. This method can be used for the fire resistance of workwear fabrics, decorative fabrics, construction tent fabrics, etc.; the 45° tilt method is suitable for aircraft interior decoration fabrics; the horizontal method is suitable for carpets and other matting fabrics and automobile interior decoration fabrics.
The oxygen index method is to place the clamped sample vertically into a transparent combustion cylinder. There is an upward moving oxygen and nitrogen gas flow in the cylinder. The upper end of the sample is ignited. The combustion phenomenon is then observed, and the continued combustion is compared with the specified limit. time or distance burned. By experimenting with a series of samples at different concentrations, low oxygen concentrations can be measured. The oxygen index method is more suitable for process experiments.
3 my country’s regulations on combustion performance
At present, countries all over the world attach great importance to the fire resistance of work clothes fabrics. Some countries have even included it in national fire safety regulations, indicating that the fire resistance of clothing fabrics has become a particularly important test in the functional inspection of work clothes. project. my country’s regulations on the fire resistance of fabrics are as follows:
As can be seen from the table, my country’s standards are based on the burning rate of fabrics. Only fabric products that meet the requirements of the above standards can be regarded as fire-resistant products. With the progress of urban modernization, to reduce fire accidents caused by fabrics, it is necessary to improve relevant laws and regulations. my country’s current fire protection product standards have been more than five years old, and there is a certain gap between the content and advanced countries. Therefore, foreign advanced standards should be carefully learned. Experience, accelerate the improvement of test method standards for the combustion performance of fabrics, formulate product standards for fire-resistant fabrics, strengthen the quality supervision and inspection of fabrics, and promote the progress of fire-resistant fabrics.
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