Combustion is an indispensable natural phenomenon in the objective world and plays an important role in daily production and life. The generation of combustion needs to meet three conditions, that is, a certain temperature, oxygen and flammable substances, all of which are indispensable. Among them, flammable substances are the bodies that can be burned, which are generally hydrocarbons, such as various biological materials such as flowers, plants and trees, or high-molecular polymers, including plastics, rubber, and fibers. Here, let's learn about rubber combustion and rubber flame retardants.
As a polymer compound, rubber has its own unique point of combustion, the process is more complicated, the combustion temperature is generally higher than other substances, mostly above 3000 degrees, the combustion process can be divided into three stages, thermal decomposition, combustion, continuous combustion. In the thermal decomposition stage, after reaching a high temperature, the rubber is depolymerized and melted, and decomposed into low-molecular-weight polymers. There will be no open fire at this stage; in the combustion stage, the thermal decomposition products are mixed with oxygen in the air, accompanied by light and heat. Combustion officially occurs and decomposes to produce carbon monoxide, carbon dioxide, and smoke. Halogen-free rubber also has a continuous combustion stage, which can promote the rubber to continue to burn until the combustible material is completely exhausted.
Flame retardants can usually play a variety of roles, such as cooling and heat absorption, isolating oxygen sources and preventing further combustion. As a special additive for rubber, they can also have the functions of plasticization, modification and filling. Commonly used flame retardants for rubber include:
1. Inorganic flame retardants
Including hydroxide, inorganic salt metal oxide and other non-combustible powders, the advantage is that the cooling and isolation effect is strong and the internal heat model can be flame-retardant by diluting the concentration of combustibles. The disadvantages are: (1) It must be used in a large amount, and too much amount may bring difficulties to the plastic of rubber; (2) The addition amount is too high, resulting in the decline of the overall performance of the rubber compound; (3) Some metal compounds may be more expensive, etc. .
2. Organic flame retardants
(1) Halogen elements: The density of hydrogen halide produced by the combustion of such substances is greater than that of air, and the sinking plays a role in isolating oxygen. The rubber mainly burns with a hydrocarbon-based structure, and the oxygen index of the halogen-containing rubber is higher than that of the halogen-free rubber. Therefore, the flame-retardant performance of the halogen-containing rubber is undisputed, but its combustion will produce corrosive and harmful effects. Toxic hydrogen halide, which is not applicable in safe situations, so other high-performance flame retardants should be developed and utilized. (2) Phosphorus flame retardant: Based on phosphate ester, it has the function of plasticization and modification. The flame retardant effect increases with the increase of carbon atoms in the alkyl group in the structure, and the overall effect is relatively good.
In the process of adding flame retardants to rubber, the coordination between flame retardant effect, performance, cost and safety should be fully considered. Therefore, the coordinated use of multiple flame retardants should be considered to complement each other's advantages and follow the principles of safety, efficiency, smoke-free and non-toxic. Combine the principles to achieve the best results.
Source: Suzhou Dongtuo Chemical Co., Ltd.
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