The flame-retardant performance of protective clothing refers to the non-flammable or non-combustible when encountering high temperature or flame. The general indicators for evaluating the flame-retardant performance of textile materials are: degree of difficulty, flame surface propagation speed, smoke visibility, toxicity and corrosivity of combustion products . The first two indicators are the main indicators for the evaluation of combustion performance. There are two main methods for testing flame retardancy of fabrics commonly used at home and abroad:
1. Vertical combustion method
The vertical combustion method is mainly used to test the combustion breadth (carbonized area and damage length), continuous combustion time and smoldering time of materials. This method is a commonly used method at home and abroad, and all countries have corresponding test standards, such as-European standard EN ISO 11611, EN ISO 11612, American standard ASTM D3659, NFPA701-1966, German standard DIN53906, British standard BS 2963A etc.
The test method is to hang a test of a certain size vertically in a prescribed combustion box, ignite it with a prescribed fire source for 12 seconds, and measure the continuous burning time and smoldering time of the experiment after removing the fire source, and calculate the damage length (carbonization length ). Among them, the continuous burning time refers to the duration of keeping a visible flame on the fabric; the smoldering time refers to the duration of keeping the flaming light on the fabric sample; the damage length refers to the material damage area under the specified experimental conditions The greater length in the direction (vertical direction).
2. Limit oxygen index method
Currently, Limiting Oxygen Index (LOI) is widely used internationally to characterize the flammability of fibers. The so-called limiting oxygen index refers to the lower volume fraction of oxygen in the oxygen-helium mixed gas required for the sample to maintain the combustion state under the specified test conditions. The larger the LOI value, the higher the concentration of oxygen required for combustion, and the harder it is to burn under normal conditions. The sample is carried out on the oxygen index tester. The method is to place a certain size sample on the sample holder in the combustion cylinder, adjust the ratio of oxygen and nitrogen, and ignite the sample with a specific igniter to make it burn for a certain period of time When the self-daughter or damage length is a certain value, it will self-extinguish. According to the oxygen and nitrogen flow rate at this time, the oxygen index value is found from the table, which is the oxygen index of the sample.