What Are The Main Components Of Flame Retardants?
There are many types of flame retardants, and the general development can be divided into two categories: organic flame retardants and inorganic flame retardants according to composition analysis. One of the organic flame retardants mainly includes halogen flame retardants, phosphorus-nitrogen flame retardants, organic phosphorus flame retardants, and silicone flame retardants. We select several types of questions for technical introduction on the research of flame retardant mechanism of flame retardant.
Halogen-based flame retardants are an important component of organic flame retardants, and their main components are halogen-based organic compounds. The free radicals generated by polymer degradation at high temperatures are the factors that maintain the combustion of organic compounds, while the hydrogen halide gas generated during the thermal decomposition of halogen flame retardants can capture free radicals, thereby preventing the flame from spreading. In addition, hydrogen halide itself cannot burn and is denser than air. It forms a gas barrier on the surface of the polymer material, which prevents the polymer material from contacting oxygen.
Phosphorus nitrogen flame retardants are mainly composed of phosphorus and nitrogen. These flame retardants are also called intumescent flame retardants, because when they are heated, they can produce a uniform layer of carbon foam on the surface of the flame retardant, which acts as a heat and oxygen barrier. Intumescent flame retardant systems generally consist of an acid source (dehydrating agent), a carbon source (carbonizing agent) and a gas source (nitrogen source, blowing agent). After heating, the esterified polyol and inorganic acid, which can be used as a dehydrating agent, are released from the acid source, and the inorganic acid reacts with the polyol (carbon source) to form an ester, which is in a viscous molten state. The water vapor produced during the reaction and the non-combustible gas produced by the gas source make the system expand and foam in the molten state. At the same time, the polyol and ester are dehydrated and carbonized to form inorganic substances and carbon slag. As the temperature rises and the reaction proceeds, the system gels and solidifies to form a porous carbon foam layer.
Inorganic flame retardants mainly include expandable graphite, hydroxide, red phosphorus or polyphosphate, etc. Generally, several different inorganic substances are mixed and used. Under high temperature, expanded graphite expands rapidly, and the surface of the polymer forms a tough carbon layer, which can separate combustibles from the heat source; when the hydroxide is heated, it absorbs a large amount of heat and releases water vapor, dilutes the combustible gas, and generates refractory metal oxidation. Red phosphorus or polyphosphate burns to produce polymetaphosphoric acid glass body, which can cover the surface of the burning body to form a protective film. At the same time, the formed phosphoric acid has strong dehydration properties and can carbonize the polymer to form a carbon isolation layer.
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