The flame retardant reaction of high polymers is a complicated process.The gas phase and the solid phase coexist.The organic reaction and the inorganic reaction proceed simultaneously.At high temperatures, many small and large molecular substances are produced and changed.
General combustion must have three conditions: ① there is a flammable substance; ② the temperature reaches the ignition point; ③ there is sufficient oxygen. As long as one of them is missing, the fire will be extinguished. The flame retardant is used for one or more of these factors Yes, flame retardant can be carried out in the following ways.
(1) An endothermic reaction occurs on the surface to produce a cooling effect
The flame retardant may undergo endothermic decomposition or endothermic reaction with the acting substance, reducing the temperature to below the temperature required for the flame to maintain its own chain reaction; or the free radicals or molecules generated by the decomposition of the flame retardant can interact with the flame The substance reacts endothermically, thereby disturbing the heat balance of combustion.
(2) Generate incombustible gas
On the one hand, the generation of non-combustible gas can exclude oxygen from the surface of the polymer; on the other hand, the flammable gas is diluted, so that the decomposition and combustion proceed in the direction of the generation of non-combustible gas.
(3) A carbonized layer is formed on the surface
The carbonized layer generated on the surface can block air, heat, etc., to prevent the combustible substances and oxygen from interdiffusing, and at the same time, the polymer can not get enough heat to decompose, so that the "fuel" generation rate is reduced.
(4) Suppress flammable gas products
Phosphate has the effect of promoting carbonization, which suppresses the generation of flammable gases.
(5) Cut off the chain reaction
Because HO• plays a very important role in combustion, adding substances that can decompose to receive free radicals can remove HO•, interfering with the chain reaction in the flame and stopping the combustion.
(6) Produce relatively dense gas
The relatively dense gas can hinder the exchange of combustion gas with air.