As an important fireproof material, intumescent fire retardant coating can effectively prevent the spread of flames and the transfer of heat by expanding into carbon when heated, thus buying precious time to protect objects and personnel. Understanding its core flame retardant mechanism is of great significance for in-depth understanding and optimization of this coating.
Intumescent fire retardant coating is usually composed of a carbonizing agent, a foaming agent, an acid source and a resin matrix. When the coating is heated, the acid source will decompose to produce acidic substances, which will cause the carbonizing agent to undergo a dehydration carbonization reaction, and the foaming agent will decompose and produce a large amount of gas when heated. Under the combined action of these reactions, the coating begins to expand and form a porous carbon foam layer.
The formed carbon foam layer has extremely low thermal conductivity and can form an effective thermal insulation barrier between the flame and the substrate. This thermal insulation layer can significantly reduce the speed of heat transfer to the substrate, slow down the temperature rise of the substrate, and thus delay the time it takes to reach the ignition point. For example, after applying intumescent fire retardant coating on the surface of wood, the carbon foam layer can effectively prevent the wood from heating up quickly and burning quickly when a fire occurs.
The gases produced by the decomposition of the foaming agent are mainly non-combustible gases such as carbon dioxide and ammonia. These gases not only expand the volume of the coating during the expansion process, but also play a role in diluting the concentration of oxygen and combustible gases in the combustion area. At the same time, they form tiny pores inside the carbon foam layer, which can hinder the contact between oxygen and combustible substances, thereby inhibiting the combustion reaction. Just like in a closed space, reducing the oxygen content will make it difficult to continue combustion, the gas produced by intumescent fire retardant coating plays a similar role.
During the combustion process, a large number of free radicals will be produced, which are the key factors in maintaining the combustion chain reaction. During the thermal decomposition process of intumescent fire retardant coating, its components may produce some substances that can capture free radicals, such as certain phosphorus and nitrogen compounds. They can react with free radicals and convert them into stable products, thereby interrupting the combustion chain reaction and making it impossible for combustion to continue.
When heated, the substrate releases flammable gases, which are one of the fuel sources for combustion. The carbon foam layer can act as a physical barrier to prevent the flammable gases in the substrate from volatilizing to the combustion area. In this way, the concentration of flammable gases in the combustion area is reduced, and combustion is difficult to continue. Taking plastic substrates as an example, the carbon foam layer formed by intumescent fire retardant coating can effectively block the flammable gases produced by the thermal decomposition of plastics, thereby inhibiting the spread of flames.
The core flame retardant mechanism of intumescent fire retardant coating expanding into charcoal when heated is a complex physical and chemical process. Through the synergistic cooperation of the carbon foam layer's heat insulation, gas dilution and barrier, free radical capture, and prevention of flammable gas volatilization, intumescent fire retardant coating can quickly form effective fire protection when a fire occurs, greatly improve the flame retardant properties of objects, and provide strong protection for fire safety. In-depth research and understanding of these mechanisms will help to further improve and optimize the performance of intumescent fire retardant coating, so that it can play a greater role in more fields.
