The wholesaler of pvc tarpaulin or pvc tarps said that when making pvc tarpaulin or pvc tarps, in order to enhance its use effect, some flame retardants will be added to it for use, and the mechanism of this flame retardant is mainly:
1) Inhibition of chain reaction: According to the chain reaction theory of combustion, free radicals are needed to maintain combustion. Flame retardants can act on the gas phase combustion zone to capture free radicals in the combustion reaction, thereby preventing the spread of flames, reducing the flame density in the combustion zone, and ultimately reducing the combustion reaction speed until it stops. For example, halogen-containing flame retardants have the same or similar evaporation temperature as the decomposition temperature of the polymer. When the polymer is decomposed by heat, the flame retardant will also volatilize at the same time. At this time, the halogen-containing flame retardant and the thermal decomposition product are in the gas phase combustion zone at the same time, and the halogen can capture the free radicals in the combustion reaction and interfere with the combustion chain reaction.
2) Covering effect: After adding flame retardant to combustible materials, the flame retardant can form a glassy or stable foam covering layer at high temperature, which can insulate oxygen, have the function of heat insulation, oxygen insulation, and prevent combustible gas from escaping outward , So as to achieve the purpose of flame retardant. For example, organic phosphorus flame retardants can produce cross-linked solid substances or carbonized layers with a more stable structure when heated. The formation of the carbonized layer can prevent the polymer from further pyrolysis, and on the other hand, it can prevent the thermal decomposition products inside it from entering the gas phase to participate in the combustion process.
3) Non-combustible gas suffocation: The flame retardant decomposes non-combustible gas when heated, and dilutes the concentration of combustible gas from combustibles below the lower combustion limit. At the same time, it also dilutes the oxygen concentration in the combustion zone, prevents the combustion from continuing, and achieves the effect of flame retardancy.
4) Endothermic effect: the heat released by any combustion in a relatively short period of time is limited. If part of the heat released by the fire source can be absorbed in a relatively short period of time, the temperature of the flame will be lowered, and it will radiate to the burning surface and the effect The amount of heat needed to crack the gasified combustible molecules into free radicals will be reduced, and the combustion reaction will be suppressed to a certain extent. Under high temperature conditions, the flame retardant has a strong endothermic reaction, absorbing part of the heat released by combustion, reducing the surface temperature of combustibles, effectively inhibiting the generation of combustible gases, and preventing the spread of combustion