Testing On The Flame Retardant Properties Of Fabrics

Almost all fabric materials are flammable, and it is difficult to prevent the fibers from burning in the flame even after being treated by fire protection. Only after the fire treatment will reduce the burning speed of the fabric material to varying degrees and quickly stop burning after leaving the fire source, so the fire prevention is relative rather than absolute.

With the progress of urban modernization, people's awareness of fire protection of fabrics is increasing. In order to reduce the fire accidents caused by fabrics and avoid unnecessary losses, the testing of fabric burning performance has received attention in the world in recent years: for fabrics. For different purposes, the old fire regulations have also been expanded from aircraft fabrics, carpets and building materials to pajamas, furniture sofa covers, taste pads and interior decorations: the United Kingdom, the United States, Japan and other countries also provide legal form: Workwear and pajamas for women, children, the elderly, and disabled people must be marked as “fireproof”. Our country’s work in this area is also constantly increasing.

1, test method of fire performance

There are various combustion test methods, and the test results of various test methods are difficult to compare with each other. The experimental results can only explain the combustion performance of the sample to a certain extent. The combustion test method is mainly used to test the combustion range (carbonization area and damage length) of the sample, the afterburning time and the smoldering time. According to the relative position of the sample and the flame, it can be divided into vertical method, tilt method and horizontal method.

China's current test for the fire performance of workwear mainly uses GB/T 5455-1997 "Vertical Method for Combustion Performance Test of Cloth Products". The principle is that a sample of a certain size is placed vertically in a prescribed combustion test chamber, and is ignited by a prescribed fire source for 12 seconds. After the fire source is removed, the sample is renewed and the smoldering time is determined. After the smoldering stops, press The prescribed method measures the length of damage. The method can be used for the fireproof performance of work clothes fabrics, decorative fabrics, cotton tent fabrics, etc.; the 45° tilt method is suitable for aircraft interior decoration fabrics; the horizontal method is applicable to carpet fabrics such as carpets and automobile interior fabrics.

The oxygen index method is to hold the sample. Vertically placed in a transparent combustion cylinder, there is an upward moving oxygen and nitrogen flow in the cylinder, igniting the sample end, and then watching the combustion phenomenon, and comparing its continuous burning time or burning distance with the specified limit: through a series of tests in different concentrations In the same experiment, the minimum oxygen concentration can be measured, and the oxygen index method is more suitable for use in process experiments.

2, the evaluation of fabric fire performance

To assess the flammability of fabrics is mainly considered from two aspects: on the one hand, the ignitability, that is, the height of the ignition point, which indicates the difficulty of the fabric on fire; on the other hand, the burning property of the fabric, that is, the fire resistance.

There are two criteria for assessing the burning performance of a fabric: one is judged from the burning rate of the fabric. That is, the fabric that has been subjected to fireproofing is contacted with the flame for a certain period of time according to a prescribed method, and then the flame is removed, and the time during which the fabric continues to burn with flame and the time of flameless burning, and the extent to which the fabric is damaged are measured. The shorter the time of flaming combustion and the time of flameless combustion, the lower the degree of damage, the better the fire resistance of the fabric; otherwise, the poor fire resistance of the fabric.

The other is judged by the oxygen index (also known as the polar oxygen index) method: oxygen is required for the combustion of the cloth, and the oxygen index (LOI) is the expression of the oxygen required for fiber combustion. Therefore, the fire resistance of the fabric can be determined by measuring the oxygen index. Performance, the higher the oxygen index, the higher the oxygen concentration required to maintain combustion, which means that the more difficult it is to burn: the index can be expressed as the minimum volume percentage of oxygen required to maintain a candle-like combustion in a mixture of nitrogen and oxygen: LOI= Oxygen concentration / (oxygen concentration + nitrogen concentration) × 100%

The oxygen index is less than 20%, which is a flammable fiber; the oxygen index is between 20% and 26%, which is a combustible fiber; the oxygen index is between 36% and 34%, which is a flame retardant fiber; and the oxygen index is more than 35%, which is an incombustible fiber.

3. China's regulations on combustion performance

At present, countries all over the world pay special attention to the fireproof performance of work-cloth fabrics. Some countries even incorporate them into national fire safety regulations, indicating that the fire performance of fabrics is a particularly important test item in the functional inspection of workwear. The regulations on fire performance of fabrics in China are as follows:

It can be seen from the table that China's standard is judged from the burning rate of fabrics, and only fabric products that meet the above requirements can be regarded as fireproof products. With the progress of urban modernization and the reduction of fire accidents caused by fabrics, it is necessary to improve relevant laws and regulations. The current standard of fire protection products in China has exceeded five years, and there is a certain gap between content and advanced households. Therefore, foreign countries should be carefully absorbed. Advanced experience, speed up the improvement of the test method standards for the burning properties of fabrics. Formulate product standards for fireproof fabrics, strengthen the quality supervision and inspection of fabrics, and promote the progress of fireproof fabrics.