Flame Retardant Polymer Materials--Research on The Mechanism of Vapor Phase Flame Retardation

Flame Retardant Polymer Materials--Research on The Mechanism of Vapor Phase Flame Retardation

Gas-phase flame retardant is a flame retardant that exerts flame retardant effect in the gas phase, thus delaying or interrupting the effect of combustion. Vapor phase flame retardant mechanism includes: Burst effect, Dilution effect, Heat removal, Oxygen isolation, Blowing out effect and other mechanisms.

1. Burst Effect

The combustion of polymer materials is a series of free radical chain reaction, which can be blocked to reduce the intensity of combustion and achieve the purpose of flame retardant. In the combustion process of flame-retardant polymer materials, the flame retardant is thermally decomposed to produce substances containing free radicals, and then the free radicals produced by the polymer material are captured to form a flame-retardant reaction product, which reduces the number of free radicals in the combustion process and achieves the purpose of blocking the free-radical chain reaction, reducing the intensity of combustion or even blocking the combustion. This phenomenon is called the burst effect, as shown in Figure 1.0.

Bromine flame retardant combustion Br-; phosphorus flame retardants, such as diethyl hypophosphite metal salt, DOPO and its derivatives and other flame retardants will be decomposed by heat to produce phosphorus compounds free radicals (such as PO-, PO2-, etc.); these free radicals can be captured in the process of combustion of polymer materials to release the H-, HO-, R-, and other important reactive free radicals, so as to prevent or slow down the progress of the combustion chain reaction, which gives polymer materials good flame retardant. These free radicals can capture the H-, HO-, R- and other important active radicals released during the combustion process of polymer materials, thus preventing or slowing down the process of combustion chain reaction, and giving the polymer materials good flame retardancy and self-extinguishing.  

2. Dilution Effect

Dilution effect refers to the thermal decomposition of flame retardants produce refractory gases (such as water vapor, NH3, N2, etc.), can be decomposed out of polymer materials to reduce the concentration of flammable gases, reduce the intensity of combustion, delay or inhibit the combustion of the material, but also to the combustion region of the concentration of oxygen to play a role in diluting the role of combustion inhibition, thus achieving the purpose of flame retardant. The mechanism is shown in Figure 2.0.

Ammonium polyphosphate will produce NH3 during thermal decomposition, diluting the concentration of combustible gases and oxygen in the gas mixture around the material and forming a gas protective layer around the combustible material; flame retardants such as zinc hydrated borate, melamine cyanurate and other flame retardants will produce water vapor, NH3, N2 and other non-flammable gases when they are heated, which can also play a role in diluting combustible gases and oxygen.

3. Heat Removal

Take away the heat is to take away part of the heat generated by the combustion of the material, reduce the temperature of the combustion area, inhibit the intensity of thermal decomposition of polymer materials, slow down the release of combustible gases, and even polymer materials can not maintain the temperature of thermal decomposition in order to produce combustible gases, weakening combustion reaction or even self-extinguishing combustion. The mechanism is shown in Figure 3.0. The way to take away the heat is divided into two kinds, one is heated to produce water vapor, take away the heat. Mainly contains a large number of hydroxide root inorganic flame retardants, such as magnesium hydroxide, aluminum hydroxide, magnesite, etc., in the process of thermal decomposition of a large number of water vapor, take away the heat of the system, to prolong the temperature to reach the ignition point of time, to achieve the effect of flame retardant. Another is to promote the decomposition of polymer materials melt, reduce the viscosity of the melt, so that the molten polymer is easy to drop, thus taking away most of the heat, and play a role in reducing the temperature of the combustion zone, and further to play a flame retardant effect. For example, the use of chlorinated paraffin and antimony oxide composed of synergistic system to flame retardant polymer, will promote the polymer material melt drop, so as to take away the heat. However, the high-temperature droplets dripping from the easy-to-melt-drop materials may ignite other substances, sometimes increasing the danger of the fire house. Therefore, in the building materials, external wall insulation materials, curtains, wall cloth and other materials are not very suitable to adopt the principle of dropping to take away the heat.

4. Oxygen isolation

Gas-phase flame retardant in the isolation of oxygen refers to the flame retardant in the combustion of the release of a larger purpose of the gas, the polymer material surface cover, blocking its contact with flammable gases and oxygen, so as to achieve the purpose of flame retardant, such as antimony trioxide and brominated epoxy resin synergistic flame retardant, can produce density greater than the air antimony triple bromide gas, the polymer material surface cover, the isolation of oxygen, so as to achieve the effect of flame retardant.

5. Blowing out effect

Blow out effect refers to flame retardant materials in the combustion process, the gas generated by the early decomposition of flame retardants in the polymer material inside the rapid formation of larger bubbles, bubbles contain a high concentration of flame retardant components, when the gas in the bubble reaches a certain volume and pressure, it will be in a very short period of time to break through the bubbles to the outside of the high-speed spray, through the centralized release of high-speed gases with flame retardant components, to achieve the purpose of rapid flame extinguishing. The mechanism is shown in Figure 5.0.The blow-out effect mainly occurs in DOPO and its derivatives used in epoxy resins. The gas generated by the decomposition of the flame retardant gathers inside the molten epoxy resin to form bubbles, and when the pressure in the bubbles reaches a certain level, the epoxy resin burns to rupture the bubbles, and the gases containing flame retardant components inside are ejected outward, which blows out the flame and achieves a good flame retardant effect.

Flame retardant flame retardant in the gas phase will contain one or more of these mechanisms, in order to achieve better flame retardant effect, two or more flame retardants can be used in conjunction with each other in the processing formula.

YINSU Flame Retardant Company is a leading supplier of high quality flame retardants. Among our flame retardants, red phosphorus flame retardant, phosphorus flame retardant intumescent flame retardant, also achieves highly efficient flame retardant effect by the mechanism of gas phase flame retardant or even both condensed phase flame retardant.