The Basic Principle of Retard Agent
Combustion properties of textiles: Under the condition of existing heat source for the vast majority of textile fibers, thermal cracking will happen, then the decomposition of the flame oxide, combust, and release a lot of heat to further promote the thermal cracking of fiber materials, so that the entire combustion cycle can continue. Oxygen index (LOI) is commonly used to represent the flammable of the fabric, the so-called LOI is the minimum volume fraction of oxygen required to maintain a candle-like combustion in the environment of nitrogen and oxygen mixtures. The higher is the Oxygen Demand index, the more difficult the fabric will burn and the better the flame-retardant is.
The mechanism of Flame Retardant Finishing
① Endothermic reaction: When the fabric is ignited, the flame retardant finishing agent coated on the surface of the fabric absorbs heat and decomposes. So that the fabric itself to keep the temperature below the ignition point, thus achieve the purpose of combustion prevention.
② The formation of free radicals: Because of its special chemical composition, flame retardants covering the surface of fabrics changes the rate of fabric burning decomposition , or generates free radicals after thermal decomposition. Then, free radicals reacts with the combustion production of fabric, thus reducing the required energy of combustion system to prevent the combustion.
③ Generating non burning gas: Because of the role of flame retardants, it will generate a number of unburned gases through the thermal decomposition, such as H2O、HCl、HBr、CO2 and so on.On the one hand, diluting the thermal decomposition of the fabric produced by the combustible gas concentration, on the other hand, isolating the oxygen and the surface of the combustion.
④ Melting theory: Under the influence of heat and energy, the flame retardant is transformed into a molten state, which forms a involatile protective layer on the surface of the fabric to isolate the air, making the air unsuitable for contacting with the fiber surface and preventing the release of combustible gas from the surface of the fiber.
⑤ Dehydration theory: For the cellulose fiber fabric, the flame retardant causes the dehydration reaction, promotes the carbonization of cellulose, suppresses the generation of combustible pyrolysis material and finally achieves the goal of flame retardant.